ext/socket/socket.c

root/ext/socket/socket.c

/* */
DEFINITIONS

This source file includes following definitions.
ruby_getaddrinfo
ruby_getaddrinfo__aix
ruby_getnameinfo__aix
init_sock
bsock_s_for_fd
bsock_shutdown
bsock_close_read
bsock_close_write
bsock_setsockopt
bsock_getsockopt
bsock_getsockname
bsock_getpeername
sendto_blocking
send_blocking
bsock_send
bsock_do_not_reverse_lookup
bsock_do_not_reverse_lookup_set
recvfrom_blocking
s_recvfrom
s_recvfrom_nonblock
bsock_recv
bsock_recv_nonblock
bsock_do_not_rev_lookup
bsock_do_not_rev_lookup_set
raise_socket_error
make_ipaddr0
make_ipaddr
make_inetaddr
str_isnumber
host_str
port_str
sock_getaddrinfo
sock_addrinfo
ipaddr
ruby_socket
wait_connectable0
try_wait_connectable
wait_connectable_ensure
wait_connectable
connect_blocking
socks_connect_blocking
ruby_connect
inetsock_cleanup
init_inetsock_internal
init_inetsock
tcp_init
socks_init
socks_s_close
make_hostent_internal
make_hostent
tcp_sockaddr
tcp_s_gethostbyname
tcp_svr_init
make_fd_nonblock
s_accept_nonblock
accept_blocking
s_accept
tcp_accept
tcp_accept_nonblock
tcp_sysaccept
unixsock_connect_internal
init_unixsock
ip_addr
ip_peeraddr
ip_recvfrom
ip_s_getaddress
udp_init
udp_connect_internal
udp_connect
udp_bind
udp_send
udp_recvfrom_nonblock
unix_init
unixpath
unix_path
unix_svr_init
unix_recvfrom
sendmsg_blocking
unix_send_io
recvmsg_blocking
unix_recv_io
unix_accept
unix_accept_nonblock
unix_sysaccept
unixaddr
unix_addr
unix_peeraddr
setup_domain_and_type
sock_initialize
sock_s_socketpair
unix_s_socketpair
sock_connect
sock_connect_nonblock
sock_bind
sock_listen
sock_recvfrom
sock_recvfrom_nonblock
sock_accept
sock_accept_nonblock
sock_sysaccept
sock_gethostname
sock_gethostname
sock_gethostname
make_addrinfo
sock_sockaddr
sock_s_gethostbyname
sock_s_gethostbyaddr
sock_s_getservbyname
sock_s_getservbyport
sock_s_getaddrinfo
sock_s_getnameinfo
sock_s_pack_sockaddr_in
sock_s_unpack_sockaddr_in
sock_s_pack_sockaddr_un
sock_s_unpack_sockaddr_un
sock_define_const
sock_define_uconst
Init_socket
/************************************************

  socket.c -

  $Author: yugui $
  created at: Thu Mar 31 12:21:29 JST 1994

  Copyright (C) 1993-2007 Yukihiro Matsumoto

************************************************/

#include "ruby/ruby.h"
#include "ruby/io.h"
#include "ruby/util.h"
#include <stdio.h>
#include <sys/types.h>

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#ifdef HAVE_SYS_UIO_H
#include <sys/uio.h>
#endif

#ifdef HAVE_XTI_H
#include <xti.h>
#endif

#ifndef _WIN32
#if defined(__BEOS__) && !defined(__HAIKU__) && !defined(BONE)
# include <net/socket.h>
#else
# include <sys/socket.h>
#endif
#include <netinet/in.h>
#ifdef HAVE_NETINET_IN_SYSTM_H
# include <netinet/in_systm.h>
#endif
#ifdef HAVE_NETINET_TCP_H
# include <netinet/tcp.h>
#endif
#ifdef HAVE_NETINET_UDP_H
# include <netinet/udp.h>
#endif
#ifdef HAVE_ARPA_INET_H
# include <arpa/inet.h>
#endif
#include <netdb.h>
#endif
#include <errno.h>
#ifdef HAVE_SYS_UN_H
#include <sys/un.h>
#endif

#if defined(HAVE_FCNTL)
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
#endif
#ifndef EWOULDBLOCK
#define EWOULDBLOCK EAGAIN
#endif
#ifndef HAVE_GETADDRINFO
# include "addrinfo.h"
#endif
#include "sockport.h"

static int do_not_reverse_lookup = 0;
#define FMODE_NOREVLOOKUP 0x100

VALUE rb_cBasicSocket;
VALUE rb_cIPSocket;
VALUE rb_cTCPSocket;
VALUE rb_cTCPServer;
VALUE rb_cUDPSocket;
#ifdef AF_UNIX
VALUE rb_cUNIXSocket;
VALUE rb_cUNIXServer;
#endif
VALUE rb_cSocket;

static VALUE rb_eSocket;

#ifdef SOCKS
VALUE rb_cSOCKSSocket;
#ifdef SOCKS5
#include <socks.h>
#else
void SOCKSinit();
int Rconnect();
#endif
#endif

#define BLOCKING_REGION(func, arg) (long)rb_thread_blocking_region((func), (arg), RUBY_UBF_IO, 0)

#define INET_CLIENT 0
#define INET_SERVER 1
#define INET_SOCKS  2

#ifndef HAVE_SOCKADDR_STORAGE
/*
 * RFC 2553: protocol-independent placeholder for socket addresses
 */
#define _SS_MAXSIZE     128
#define _SS_ALIGNSIZE   (sizeof(double))
#define _SS_PAD1SIZE    (_SS_ALIGNSIZE - sizeof(unsigned char) * 2)
#define _SS_PAD2SIZE    (_SS_MAXSIZE - sizeof(unsigned char) * 2 - \
                                _SS_PAD1SIZE - _SS_ALIGNSIZE)

struct sockaddr_storage {
#ifdef HAVE_SA_LEN
        unsigned char ss_len;           /* address length */
        unsigned char ss_family;        /* address family */
#else
        unsigned short ss_family;
#endif
        char    __ss_pad1[_SS_PAD1SIZE];
        double  __ss_align;     /* force desired structure storage alignment */
        char    __ss_pad2[_SS_PAD2SIZE];
};
#endif

#if defined(INET6) && (defined(LOOKUP_ORDER_HACK_INET) || defined(LOOKUP_ORDER_HACK_INET6))
#define LOOKUP_ORDERS (sizeof(lookup_order_table) / sizeof(lookup_order_table[0]))
static const int lookup_order_table[] = {
#if defined(LOOKUP_ORDER_HACK_INET)
    PF_INET, PF_INET6, PF_UNSPEC,
#elif defined(LOOKUP_ORDER_HACK_INET6)
    PF_INET6, PF_INET, PF_UNSPEC,
#else
    /* should not happen */
#endif
};

static int
ruby_getaddrinfo(char *nodename, char *servname,
                 struct addrinfo *hints, struct addrinfo **res)
{
    struct addrinfo tmp_hints;
    int i, af, error;

    if (hints->ai_family != PF_UNSPEC) {
        return getaddrinfo(nodename, servname, hints, res);
    }

    for (i = 0; i < LOOKUP_ORDERS; i++) {
        af = lookup_order_table[i];
        MEMCPY(&tmp_hints, hints, struct addrinfo, 1);
        tmp_hints.ai_family = af;
        error = getaddrinfo(nodename, servname, &tmp_hints, res);
        if (error) {
            if (tmp_hints.ai_family == PF_UNSPEC) {
                break;
            }
        }
        else {
            break;
        }
    }

    return error;
}
#define getaddrinfo(node,serv,hints,res) ruby_getaddrinfo((node),(serv),(hints),(res))
#endif

#if defined(_AIX)
static int
ruby_getaddrinfo__aix(char *nodename, char *servname,
                      struct addrinfo *hints, struct addrinfo **res)
{
    int error = getaddrinfo(nodename, servname, hints, res);
    struct addrinfo *r;
    if (error)
        return error;
    for (r = *res; r != NULL; r = r->ai_next) {
        if (r->ai_addr->sa_family == 0)
            r->ai_addr->sa_family = r->ai_family;
        if (r->ai_addr->sa_len == 0)
            r->ai_addr->sa_len = r->ai_addrlen;
    }
    return 0;
}
#undef getaddrinfo
#define getaddrinfo(node,serv,hints,res) ruby_getaddrinfo__aix((node),(serv),(hints),(res))
static int
ruby_getnameinfo__aix(sa, salen, host, hostlen, serv, servlen, flags)
     const struct sockaddr *sa;
     size_t salen;
     char *host;
     size_t hostlen;
     char *serv;
     size_t servlen;
     int flags;
{
  struct sockaddr_in6 *sa6;
  u_int32_t *a6;

  if (sa->sa_family == AF_INET6) {
    sa6 = (struct sockaddr_in6 *)sa;
    a6 = sa6->sin6_addr.u6_addr.u6_addr32;

    if (a6[0] == 0 && a6[1] == 0 && a6[2] == 0 && a6[3] == 0) {
      strncpy(host, "::", hostlen);
      snprintf(serv, servlen, "%d", sa6->sin6_port);
      return 0;
    }
  }
  return getnameinfo(sa, salen, host, hostlen, serv, servlen, flags);
}
#undef getnameinfo
#define getnameinfo(sa, salen, host, hostlen, serv, servlen, flags) \
            ruby_getnameinfo__aix((sa), (salen), (host), (hostlen), (serv), (servlen), (flags))
#ifndef CMSG_SPACE
# define CMSG_SPACE(len) (_CMSG_ALIGN(sizeof(struct cmsghdr)) + _CMSG_ALIGN(len))
#endif
#ifndef CMSG_LEN
# define CMSG_LEN(len) (_CMSG_ALIGN(sizeof(struct cmsghdr)) + (len))
#endif
#endif

#ifdef __BEOS__
#undef close
#define close closesocket
#endif

static VALUE
init_sock(VALUE sock, int fd)
{
    rb_io_t *fp;

    MakeOpenFile(sock, fp);
    fp->fd = fd;
    fp->mode = FMODE_READWRITE|FMODE_DUPLEX;
    rb_io_ascii8bit_binmode(sock);
    if (do_not_reverse_lookup) {
        fp->mode |= FMODE_NOREVLOOKUP;
    }
    rb_io_synchronized(fp);

    return sock;
}

static VALUE
bsock_s_for_fd(VALUE klass, VALUE fd)
{
    rb_io_t *fptr;
    VALUE sock = init_sock(rb_obj_alloc(klass), NUM2INT(fd));

    GetOpenFile(sock, fptr);

    return sock;
}

static VALUE
bsock_shutdown(int argc, VALUE *argv, VALUE sock)
{
    VALUE howto;
    int how;
    rb_io_t *fptr;

    if (rb_safe_level() >= 4 && !OBJ_TAINTED(sock)) {
        rb_raise(rb_eSecurityError, "Insecure: can't shutdown socket");
    }
    rb_scan_args(argc, argv, "01", &howto);
    if (howto == Qnil)
        how = 2;
    else {
        how = NUM2INT(howto);
        if (how < 0 || 2 < how) {
            rb_raise(rb_eArgError, "`how' should be either 0, 1, 2");
        }
    }
    GetOpenFile(sock, fptr);
    if (shutdown(fptr->fd, how) == -1)
        rb_sys_fail(0);

    return INT2FIX(0);
}

static VALUE
bsock_close_read(VALUE sock)
{
    rb_io_t *fptr;

    if (rb_safe_level() >= 4 && !OBJ_TAINTED(sock)) {
        rb_raise(rb_eSecurityError, "Insecure: can't close socket");
    }
    GetOpenFile(sock, fptr);
    shutdown(fptr->fd, 0);
    if (!(fptr->mode & FMODE_WRITABLE)) {
        return rb_io_close(sock);
    }
    fptr->mode &= ~FMODE_READABLE;

    return Qnil;
}

static VALUE
bsock_close_write(VALUE sock)
{
    rb_io_t *fptr;

    if (rb_safe_level() >= 4 && !OBJ_TAINTED(sock)) {
        rb_raise(rb_eSecurityError, "Insecure: can't close socket");
    }
    GetOpenFile(sock, fptr);
    if (!(fptr->mode & FMODE_READABLE)) {
        return rb_io_close(sock);
    }
    shutdown(fptr->fd, 1);
    fptr->mode &= ~FMODE_WRITABLE;

    return Qnil;
}

/*
 * Document-method: setsockopt
 * call-seq: setsockopt(level, optname, optval)
 *
 * Sets a socket option. These are protocol and system specific, see your
 * local sytem documentation for details.
 *
 * === Parameters
 * * +level+ is an integer, usually one of the SOL_ constants such as
 *   Socket::SOL_SOCKET, or a protocol level.
 * * +optname+ is an integer, usually one of the SO_ constants, such
 *   as Socket::SO_REUSEADDR.
 * * +optval+ is the value of the option, it is passed to the underlying
 *   setsockopt() as a pointer to a certain number of bytes. How this is
 *   done depends on the type:
 *   - Fixnum: value is assigned to an int, and a pointer to the int is
 *     passed, with length of sizeof(int).
 *   - true or false: 1 or 0 (respectively) is assigned to an int, and the
 *     int is passed as for a Fixnum. Note that +false+ must be passed,
 *     not +nil+.
 *   - String: the string's data and length is passed to the socket.
 *
 * === Examples
 *
 * Some socket options are integers with boolean values, in this case
 * #setsockopt could be called like this:
 *   sock.setsockopt(Socket::SOL_SOCKET,Socket::SO_REUSEADDR, true)
 *
 * Some socket options are integers with numeric values, in this case
 * #setsockopt could be called like this:
 *   sock.setsockopt(Socket::IPPROTO_IP, Socket::IP_TTL, 255)
 *
 * Option values may be structs. Passing them can be complex as it involves
 * examining your system headers to determine the correct definition. An
 * example is an +ip_mreq+, which may be defined in your system headers as:
 *   struct ip_mreq {
 *     struct  in_addr imr_multiaddr;
 *     struct  in_addr imr_interface;
 *   };
 * 
 * In this case #setsockopt could be called like this:
 *   optval =  IPAddr.new("224.0.0.251") + Socket::INADDR_ANY
 *   sock.setsockopt(Socket::IPPROTO_IP, Socket::IP_ADD_MEMBERSHIP, optval)
 *
*/
static VALUE
bsock_setsockopt(VALUE sock, VALUE lev, VALUE optname, VALUE val)
{
    int level, option;
    rb_io_t *fptr;
    int i;
    char *v;
    int vlen;

    rb_secure(2);
    level = NUM2INT(lev);
    option = NUM2INT(optname);

    switch (TYPE(val)) {
      case T_FIXNUM:
        i = FIX2INT(val);
        goto numval;
      case T_FALSE:
        i = 0;
        goto numval;
      case T_TRUE:
        i = 1;
      numval:
        v = (char*)&i; vlen = sizeof(i);
        break;
      default:
        StringValue(val);
        v = RSTRING_PTR(val);
        vlen = RSTRING_LEN(val);
        break;
    }

#define rb_sys_fail_path(path) rb_sys_fail(NIL_P(path) ? 0 : RSTRING_PTR(path))

    GetOpenFile(sock, fptr);
    if (setsockopt(fptr->fd, level, option, v, vlen) < 0)
        rb_sys_fail_path(fptr->pathv);

    return INT2FIX(0);
}

/*
 * Document-method: getsockopt
 * call-seq: getsockopt(level, optname)
 *
 * Gets a socket option. These are protocol and system specific, see your
 * local sytem documentation for details. The option is returned as
 * a String with the data being the binary value of the socket option.
 *
 * === Parameters
 * * +level+ is an integer, usually one of the SOL_ constants such as
 *   Socket::SOL_SOCKET, or a protocol level.
 * * +optname+ is an integer, usually one of the SO_ constants, such
 *   as Socket::SO_REUSEADDR.
 *
 * === Examples
 *
 * Some socket options are integers with boolean values, in this case
 * #getsockopt could be called like this:
 *   optval = sock.getsockopt(Socket::SOL_SOCKET,Socket::SO_REUSEADDR)
 *   optval = optval.unpack "i"
 *   reuseaddr = optval[0] == 0 ? false : true
 *
 * Some socket options are integers with numeric values, in this case
 * #getsockopt could be called like this:
 *   optval = sock.getsockopt(Socket::IPPROTO_IP, Socket::IP_TTL)
 *   ipttl = optval.unpack("i")[0]
 *
 * Option values may be structs. Decoding them can be complex as it involves
 * examining your system headers to determine the correct definition. An
 * example is a +struct linger+, which may be defined in your system headers
 * as:
 *   struct linger {
 *     int l_onoff;
 *     int l_linger;
 *   };
 * 
 * In this case #getsockopt could be called like this:
 *   optval =  sock.getsockopt(Socket::SOL_SOCKET, Socket::SO_LINGER)
 *   onoff, linger = optval.unpack "ii"
*/
static VALUE
bsock_getsockopt(VALUE sock, VALUE lev, VALUE optname)
{
#if !defined(__BEOS__)
    int level, option;
    socklen_t len;
    char *buf;
    rb_io_t *fptr;

    level = NUM2INT(lev);
    option = NUM2INT(optname);
    len = 256;
    buf = ALLOCA_N(char,len);

    GetOpenFile(sock, fptr);
    if (getsockopt(fptr->fd, level, option, buf, &len) < 0)
        rb_sys_fail_path(fptr->pathv);

    return rb_str_new(buf, len);
#else
    rb_notimplement();
#endif
}

static VALUE
bsock_getsockname(VALUE sock)
{
    char buf[1024];
    socklen_t len = sizeof buf;
    rb_io_t *fptr;

    GetOpenFile(sock, fptr);
    if (getsockname(fptr->fd, (struct sockaddr*)buf, &len) < 0)
        rb_sys_fail("getsockname(2)");
    return rb_str_new(buf, len);
}

static VALUE
bsock_getpeername(VALUE sock)
{
    char buf[1024];
    socklen_t len = sizeof buf;
    rb_io_t *fptr;

    GetOpenFile(sock, fptr);
    if (getpeername(fptr->fd, (struct sockaddr*)buf, &len) < 0)
        rb_sys_fail("getpeername(2)");
    return rb_str_new(buf, len);
}

struct send_arg {
    int fd, flags;
    VALUE mesg;
    struct sockaddr *to;
    socklen_t tolen;
};

static VALUE
sendto_blocking(void *data)
{
    struct send_arg *arg = data;
    VALUE mesg = arg->mesg;
    return (VALUE)sendto(arg->fd, RSTRING_PTR(mesg), RSTRING_LEN(mesg),
                         arg->flags, arg->to, arg->tolen);
}

static VALUE
send_blocking(void *data)
{
    struct send_arg *arg = data;
    VALUE mesg = arg->mesg;
    return (VALUE)send(arg->fd, RSTRING_PTR(mesg), RSTRING_LEN(mesg),
                       arg->flags);
}

static VALUE
bsock_send(int argc, VALUE *argv, VALUE sock)
{
    struct send_arg arg;
    VALUE flags, to;
    rb_io_t *fptr;
    int n;
    rb_blocking_function_t *func;

    rb_secure(4);
    rb_scan_args(argc, argv, "21", &arg.mesg, &flags, &to);

    StringValue(arg.mesg);
    if (!NIL_P(to)) {
        StringValue(to);
        to = rb_str_new4(to);
        arg.to = (struct sockaddr *)RSTRING_PTR(to);
        arg.tolen = RSTRING_LEN(to);
        func = sendto_blocking;
    }
    else {
        func = send_blocking;
    }
    GetOpenFile(sock, fptr);
    arg.fd = fptr->fd;
    arg.flags = NUM2INT(flags);
    while (rb_thread_fd_writable(arg.fd),
           (n = (int)BLOCKING_REGION(func, &arg)) < 0) {
        if (rb_io_wait_writable(arg.fd)) {
            continue;
        }
        rb_sys_fail("send(2)");
    }
    return INT2FIX(n);
}

static VALUE
bsock_do_not_reverse_lookup(VALUE sock)
{
    rb_io_t *fptr;

    GetOpenFile(sock, fptr);
    return (fptr->mode & FMODE_NOREVLOOKUP) ? Qtrue : Qfalse;
}

static VALUE
bsock_do_not_reverse_lookup_set(VALUE sock, VALUE state)
{
    rb_io_t *fptr;

    rb_secure(4);
    GetOpenFile(sock, fptr);
    if (RTEST(state)) {
        fptr->mode |= FMODE_NOREVLOOKUP;
    }
    else {
        fptr->mode &= ~FMODE_NOREVLOOKUP;
    }
    return sock;
}

static VALUE ipaddr(struct sockaddr*, int);
#ifdef HAVE_SYS_UN_H
static VALUE unixaddr(struct sockaddr_un*, socklen_t);
#endif

enum sock_recv_type {
    RECV_RECV,                  /* BasicSocket#recv(no from) */
    RECV_IP,                    /* IPSocket#recvfrom */
    RECV_UNIX,                  /* UNIXSocket#recvfrom */
    RECV_SOCKET                 /* Socket#recvfrom */
};

struct recvfrom_arg {
    int fd, flags;
    VALUE str;
    socklen_t alen;
    char buf[1024];
};

static VALUE
recvfrom_blocking(void *data)
{
    struct recvfrom_arg *arg = data;
    return (VALUE)recvfrom(arg->fd, RSTRING_PTR(arg->str), RSTRING_LEN(arg->str),
                           arg->flags, (struct sockaddr*)arg->buf, &arg->alen);
}

static VALUE
s_recvfrom(VALUE sock, int argc, VALUE *argv, enum sock_recv_type from)
{
    rb_io_t *fptr;
    VALUE str, klass;
    struct recvfrom_arg arg;
    VALUE len, flg;
    long buflen;
    long slen;

    rb_scan_args(argc, argv, "11", &len, &flg);

    if (flg == Qnil) arg.flags = 0;
    else             arg.flags = NUM2INT(flg);
    buflen = NUM2INT(len);

    GetOpenFile(sock, fptr);
    if (rb_io_read_pending(fptr)) {
        rb_raise(rb_eIOError, "recv for buffered IO");
    }
    arg.fd = fptr->fd;
    arg.alen = sizeof(arg.buf);

    arg.str = str = rb_tainted_str_new(0, buflen);
    klass = RBASIC(str)->klass;
    RBASIC(str)->klass = 0;

    while (rb_io_check_closed(fptr),
           rb_thread_wait_fd(arg.fd),
           (slen = BLOCKING_REGION(recvfrom_blocking, &arg)) < 0) {
        if (RBASIC(str)->klass || RSTRING_LEN(str) != buflen) {
            rb_raise(rb_eRuntimeError, "buffer string modified");
        }
    }

    RBASIC(str)->klass = klass;
    if (slen < RSTRING_LEN(str)) {
        rb_str_set_len(str, slen);
    }
    rb_obj_taint(str);
    switch (from) {
      case RECV_RECV:
        return str;
      case RECV_IP:
#if 0
        if (arg.alen != sizeof(struct sockaddr_in)) {
            rb_raise(rb_eTypeError, "sockaddr size differs - should not happen");
        }
#endif
        if (arg.alen && arg.alen != sizeof(arg.buf)) /* OSX doesn't return a from result for connection-oriented sockets */
            return rb_assoc_new(str, ipaddr((struct sockaddr*)arg.buf, fptr->mode & FMODE_NOREVLOOKUP));
        else
            return rb_assoc_new(str, Qnil);

#ifdef HAVE_SYS_UN_H
      case RECV_UNIX:
        return rb_assoc_new(str, unixaddr((struct sockaddr_un*)arg.buf, arg.alen));
#endif
      case RECV_SOCKET:
        return rb_assoc_new(str, rb_str_new(arg.buf, arg.alen));
      default:
        rb_bug("s_recvfrom called with bad value");
    }
}

static VALUE
s_recvfrom_nonblock(VALUE sock, int argc, VALUE *argv, enum sock_recv_type from)
{
    rb_io_t *fptr;
    VALUE str;
    char buf[1024];
    socklen_t alen = sizeof buf;
    VALUE len, flg;
    long buflen;
    long slen;
    int fd, flags;
    VALUE addr = Qnil;

    rb_scan_args(argc, argv, "11", &len, &flg);

    if (flg == Qnil) flags = 0;
    else             flags = NUM2INT(flg);
    buflen = NUM2INT(len);

#ifdef MSG_DONTWAIT
    /* MSG_DONTWAIT avoids the race condition between fcntl and recvfrom.
       It is not portable, though. */
    flags |= MSG_DONTWAIT;
#endif

    GetOpenFile(sock, fptr);
    if (rb_io_read_pending(fptr)) {
        rb_raise(rb_eIOError, "recvfrom for buffered IO");
    }
    fd = fptr->fd;

    str = rb_tainted_str_new(0, buflen);

    rb_io_check_closed(fptr);
    rb_io_set_nonblock(fptr);
    slen = recvfrom(fd, RSTRING_PTR(str), buflen, flags, (struct sockaddr*)buf, &alen);

    if (slen < 0) {
        rb_sys_fail("recvfrom(2)");
    }
    if (slen < RSTRING_LEN(str)) {
        rb_str_set_len(str, slen);
    }
    rb_obj_taint(str);
    switch (from) {
      case RECV_RECV:
        return str;

      case RECV_IP:
        if (alen && alen != sizeof(buf)) /* connection-oriented socket may not return a from result */
            addr = ipaddr((struct sockaddr*)buf, fptr->mode & FMODE_NOREVLOOKUP);
        break;

      case RECV_SOCKET:
        addr = rb_str_new(buf, alen);
        break;

      default:
        rb_bug("s_recvfrom_nonblock called with bad value");
    }
    return rb_assoc_new(str, addr);
}

static VALUE
bsock_recv(int argc, VALUE *argv, VALUE sock)
{
    return s_recvfrom(sock, argc, argv, RECV_RECV);
}

/*
 * call-seq:
 *      basicsocket.recv_nonblock(maxlen) => mesg
 *      basicsocket.recv_nonblock(maxlen, flags) => mesg
 * 
 * Receives up to _maxlen_ bytes from +socket+ using recvfrom(2) after
 * O_NONBLOCK is set for the underlying file descriptor.
 * _flags_ is zero or more of the +MSG_+ options.
 * The result, _mesg_, is the data received.
 *
 * When recvfrom(2) returns 0, Socket#recv_nonblock returns
 * an empty string as data.
 * The meaning depends on the socket: EOF on TCP, empty packet on UDP, etc.
 * 
 * === Parameters
 * * +maxlen+ - the number of bytes to receive from the socket
 * * +flags+ - zero or more of the +MSG_+ options 
 * 
 * === Example
 *      serv = TCPServer.new("127.0.0.1", 0)
 *      af, port, host, addr = serv.addr
 *      c = TCPSocket.new(addr, port)
 *      s = serv.accept
 *      c.send "aaa", 0
 *      IO.select([s]) # emulate blocking recv.
 *      p s.recv_nonblock(10) #=> "aaa"
 *
 * Refer to Socket#recvfrom for the exceptions that may be thrown if the call
 * to _recv_nonblock_ fails. 
 *
 * BasicSocket#recv_nonblock may raise any error corresponding to recvfrom(2) failure,
 * including Errno::EWOULDBLOCK.
 *
 * === See
 * * Socket#recvfrom
 */

static VALUE
bsock_recv_nonblock(int argc, VALUE *argv, VALUE sock)
{
    return s_recvfrom_nonblock(sock, argc, argv, RECV_RECV);
}

static VALUE
bsock_do_not_rev_lookup(void)
{
    return do_not_reverse_lookup?Qtrue:Qfalse;
}

static VALUE
bsock_do_not_rev_lookup_set(VALUE self, VALUE val)
{
    rb_secure(4);
    do_not_reverse_lookup = RTEST(val);
    return val;
}

NORETURN(static void raise_socket_error(const char *, int));
static void
raise_socket_error(const char *reason, int error)
{
#ifdef EAI_SYSTEM
    if (error == EAI_SYSTEM) rb_sys_fail(reason);
#endif
    rb_raise(rb_eSocket, "%s: %s", reason, gai_strerror(error));
}

static void
make_ipaddr0(struct sockaddr *addr, char *buf, size_t len)
{
    int error;

    error = getnameinfo(addr, SA_LEN(addr), buf, len, NULL, 0, NI_NUMERICHOST);
    if (error) {
        raise_socket_error("getnameinfo", error);
    }
}

static VALUE
make_ipaddr(struct sockaddr *addr)
{
    char buf[1024];

    make_ipaddr0(addr, buf, sizeof(buf));
    return rb_str_new2(buf);
}

static void
make_inetaddr(long host, char *buf, size_t len)
{
    struct sockaddr_in sin;

    MEMZERO(&sin, struct sockaddr_in, 1);
    sin.sin_family = AF_INET;
    SET_SIN_LEN(&sin, sizeof(sin));
    sin.sin_addr.s_addr = host;
    make_ipaddr0((struct sockaddr*)&sin, buf, len);
}

static int
str_isnumber(const char *p)
{
    char *ep;

    if (!p || *p == '\0')
       return 0;
    ep = NULL;
    (void)STRTOUL(p, &ep, 10);
    if (ep && *ep == '\0')
       return 1;
    else
       return 0;
}

static char*
host_str(VALUE host, char *hbuf, size_t len)
{
    if (NIL_P(host)) {
        return NULL;
    }
    else if (rb_obj_is_kind_of(host, rb_cInteger)) {
        unsigned long i = NUM2ULONG(host);

        make_inetaddr(htonl(i), hbuf, len);
        return hbuf;
    }
    else {
        char *name;

        SafeStringValue(host);
        name = RSTRING_PTR(host);
        if (!name || *name == 0 || (name[0] == '<' && strcmp(name, "<any>") == 0)) {
            make_inetaddr(INADDR_ANY, hbuf, len);
        }
        else if (name[0] == '<' && strcmp(name, "<broadcast>") == 0) {
            make_inetaddr(INADDR_BROADCAST, hbuf, len);
        }
        else if (strlen(name) >= len) {
            rb_raise(rb_eArgError, "hostname too long (%"PRIuSIZE")",
                strlen(name));
        }
        else {
            strcpy(hbuf, name);
        }
        return hbuf;
    }
}

static char*
port_str(VALUE port, char *pbuf, size_t len)
{
    if (NIL_P(port)) {
        return 0;
    }
    else if (FIXNUM_P(port)) {
        snprintf(pbuf, len, "%ld", FIX2LONG(port));
        return pbuf;
    }
    else {
        char *serv;

        SafeStringValue(port);
        serv = RSTRING_PTR(port);
        if (strlen(serv) >= len) {
            rb_raise(rb_eArgError, "service name too long (%"PRIuSIZE")",
                strlen(serv));
        }
        strcpy(pbuf, serv);
        return pbuf;
    }
}

#ifndef NI_MAXHOST
# define NI_MAXHOST 1025
#endif
#ifndef NI_MAXSERV
# define NI_MAXSERV 32
#endif

static struct addrinfo*
sock_getaddrinfo(VALUE host, VALUE port, struct addrinfo *hints, int socktype_hack)
{
    struct addrinfo* res = NULL;
    char *hostp, *portp;
    int error;
    char hbuf[NI_MAXHOST], pbuf[NI_MAXSERV];

    hostp = host_str(host, hbuf, sizeof(hbuf));
    portp = port_str(port, pbuf, sizeof(pbuf));

    if (socktype_hack && hints->ai_socktype == 0 && hints->ai_flags == 0 && str_isnumber(portp)) {
       hints->ai_socktype = SOCK_DGRAM;
    }

    error = getaddrinfo(hostp, portp, hints, &res);
    if (error) {
        if (hostp && hostp[strlen(hostp)-1] == '\n') {
            rb_raise(rb_eSocket, "newline at the end of hostname");
        }
        raise_socket_error("getaddrinfo", error);
    }

#if defined(__APPLE__) && defined(__MACH__)
    {
        struct addrinfo *r;
        r = res;
        while (r) {
            if (! r->ai_socktype) r->ai_socktype = hints->ai_socktype;
            if (! r->ai_protocol) {
                if (r->ai_socktype == SOCK_DGRAM) {
                    r->ai_protocol = IPPROTO_UDP;
                }
                else if (r->ai_socktype == SOCK_STREAM) {
                    r->ai_protocol = IPPROTO_TCP;
                }
            }
            r = r->ai_next;
        }
    }
#endif
    return res;
}

static struct addrinfo*
sock_addrinfo(VALUE host, VALUE port, int socktype, int flags)
{
    struct addrinfo hints;

    MEMZERO(&hints, struct addrinfo, 1);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = socktype;
    hints.ai_flags = flags;
    return sock_getaddrinfo(host, port, &hints, 1);
}

static VALUE
ipaddr(struct sockaddr *sockaddr, int norevlookup)
{
    VALUE family, port, addr1, addr2;
    VALUE ary;
    int error;
    char hbuf[1024], pbuf[1024];

    switch (sockaddr->sa_family) {
    case AF_UNSPEC:
        family = rb_str_new2("AF_UNSPEC");
        break;
    case AF_INET:
        family = rb_str_new2("AF_INET");
        break;
#ifdef INET6
    case AF_INET6:
        family = rb_str_new2("AF_INET6");
        break;
#endif
#ifdef AF_LOCAL
    case AF_LOCAL:
        family = rb_str_new2("AF_LOCAL");
        break;
#elif  AF_UNIX
    case AF_UNIX:
        family = rb_str_new2("AF_UNIX");
        break;
#endif
    default:
        sprintf(pbuf, "unknown:%d", sockaddr->sa_family);
        family = rb_str_new2(pbuf);
        break;
    }

    addr1 = Qnil;
    if (!norevlookup) {
        error = getnameinfo(sockaddr, SA_LEN(sockaddr), hbuf, sizeof(hbuf),
                            NULL, 0, 0);
        if (! error) {
            addr1 = rb_str_new2(hbuf);
        }
    }
    error = getnameinfo(sockaddr, SA_LEN(sockaddr), hbuf, sizeof(hbuf),
                        pbuf, sizeof(pbuf), NI_NUMERICHOST | NI_NUMERICSERV);
    if (error) {
        raise_socket_error("getnameinfo", error);
    }
    addr2 = rb_str_new2(hbuf);
    if (addr1 == Qnil) {
        addr1 = addr2;
    }
    port = INT2FIX(atoi(pbuf));
    ary = rb_ary_new3(4, family, port, addr1, addr2);

    return ary;
}

static int
ruby_socket(int domain, int type, int proto)
{
    int fd;

    fd = socket(domain, type, proto);
    if (fd < 0) {
        if (errno == EMFILE || errno == ENFILE) {
            rb_gc();
            fd = socket(domain, type, proto);
        }
    }
    return fd;
}

static int
wait_connectable0(int fd, rb_fdset_t *fds_w, rb_fdset_t *fds_e)
{
    int sockerr;
    socklen_t sockerrlen;

    for (;;) {
        rb_fd_zero(fds_w);
        rb_fd_zero(fds_e);

        rb_fd_set(fd, fds_w);
        rb_fd_set(fd, fds_e);

        rb_thread_select(fd+1, 0, rb_fd_ptr(fds_w), rb_fd_ptr(fds_e), 0);

        if (rb_fd_isset(fd, fds_w)) {
            return 0;
        }
        else if (rb_fd_isset(fd, fds_e)) {
            sockerrlen = sizeof(sockerr);
            if (getsockopt(fd, SOL_SOCKET, SO_ERROR, (void *)&sockerr,
                           &sockerrlen) == 0) {
                if (sockerr == 0)
                    continue;   /* workaround for winsock */
                errno = sockerr;
            }
            return -1;
        }
    }

    return 0;
}

struct wait_connectable_arg {
    int fd;
    rb_fdset_t fds_w;
    rb_fdset_t fds_e;
};

#ifdef HAVE_RB_FD_INIT
static VALUE
try_wait_connectable(VALUE arg)
{
    struct wait_connectable_arg *p = (struct wait_connectable_arg *)arg;
    return (VALUE)wait_connectable0(p->fd, &p->fds_w, &p->fds_e);
}

static VALUE
wait_connectable_ensure(VALUE arg)
{
    struct wait_connectable_arg *p = (struct wait_connectable_arg *)arg;
    rb_fd_term(&p->fds_w);
    rb_fd_term(&p->fds_e);
    return Qnil;
}
#endif

static int
wait_connectable(int fd)
{
    struct wait_connectable_arg arg;

    rb_fd_init(&arg.fds_w);
    rb_fd_init(&arg.fds_e);
#ifdef HAVE_RB_FD_INIT
    arg.fd = fd;
    return (int)rb_ensure(try_wait_connectable, (VALUE)&arg,
                          wait_connectable_ensure,(VALUE)&arg);
#else
    return wait_connectable0(fd, &arg.fds_w, &arg.fds_e);
#endif
}

#ifdef __CYGWIN__
#define WAIT_IN_PROGRESS 10
#endif
#ifdef __APPLE__
#define WAIT_IN_PROGRESS 10
#endif
#ifdef __linux__
/* returns correct error */
#define WAIT_IN_PROGRESS 0
#endif
#ifndef WAIT_IN_PROGRESS
/* BSD origin code apparently has a problem */
#define WAIT_IN_PROGRESS 1
#endif

struct connect_arg {
    int fd;
    const struct sockaddr *sockaddr;
    socklen_t len;
};

static VALUE
connect_blocking(void *data)
{
    struct connect_arg *arg = data;
    return (VALUE)connect(arg->fd, arg->sockaddr, arg->len);
}

#if defined(SOCKS) && !defined(SOCKS5)
static VALUE
socks_connect_blocking(void *data)
{
    struct connect_arg *arg = data;
    return (VALUE)Rconnect(arg->fd, arg->sockaddr, arg->len);
}
#endif

static int
ruby_connect(int fd, const struct sockaddr *sockaddr, int len, int socks)
{
    int status;
    rb_blocking_function_t *func = connect_blocking;
    struct connect_arg arg;
#if WAIT_IN_PROGRESS > 0
    int wait_in_progress = -1;
    int sockerr;
    socklen_t sockerrlen;
#endif

    arg.fd = fd;
    arg.sockaddr = sockaddr;
    arg.len = len;
#if defined(SOCKS) && !defined(SOCKS5)
    if (socks) func = socks_connect_blocking;
#endif
    for (;;) {
        status = (int)BLOCKING_REGION(func, &arg);
        if (status < 0) {
            switch (errno) {
              case EAGAIN:
#ifdef EINPROGRESS
              case EINPROGRESS:
#endif
#if WAIT_IN_PROGRESS > 0
                sockerrlen = sizeof(sockerr);
                status = getsockopt(fd, SOL_SOCKET, SO_ERROR, (void *)&sockerr, &sockerrlen);
                if (status) break;
                if (sockerr) {
                    status = -1;
                    errno = sockerr;
                    break;
                }
#endif
#ifdef EALREADY
              case EALREADY:
#endif
#if WAIT_IN_PROGRESS > 0
                wait_in_progress = WAIT_IN_PROGRESS;
#endif
                status = wait_connectable(fd);
                if (status) {
                    break;
                }
                errno = 0;
                continue;

#if WAIT_IN_PROGRESS > 0
              case EINVAL:
                if (wait_in_progress-- > 0) {
                    /*
                     * connect() after EINPROGRESS returns EINVAL on
                     * some platforms, need to check true error
                     * status.
                     */
                    sockerrlen = sizeof(sockerr);
                    status = getsockopt(fd, SOL_SOCKET, SO_ERROR, (void *)&sockerr, &sockerrlen);
                    if (!status && !sockerr) {
                        struct timeval tv = {0, 100000};
                        rb_thread_wait_for(tv);
                        continue;
                    }
                    status = -1;
                    errno = sockerr;
                }
                break;
#endif

#ifdef EISCONN
              case EISCONN:
                status = 0;
                errno = 0;
                break;
#endif
              default:
                break;
            }
        }
        return status;
    }
}

struct inetsock_arg
{
    VALUE sock;
    struct {
        VALUE host, serv;
        struct addrinfo *res;
    } remote, local;
    int type;
    int fd;
};

static VALUE
inetsock_cleanup(struct inetsock_arg *arg)
{
    if (arg->remote.res) {
        freeaddrinfo(arg->remote.res);
        arg->remote.res = 0;
    }
    if (arg->local.res) {
        freeaddrinfo(arg->local.res);
        arg->local.res = 0;
    }
    if (arg->fd >= 0) {
        close(arg->fd);
    }
    return Qnil;
}

static VALUE
init_inetsock_internal(struct inetsock_arg *arg)
{
    int type = arg->type;
    struct addrinfo *res;
    int fd, status = 0;
    const char *syscall = 0;

    arg->remote.res = sock_addrinfo(arg->remote.host, arg->remote.serv, SOCK_STREAM,
                                    (type == INET_SERVER) ? AI_PASSIVE : 0);
    /*
     * Maybe also accept a local address
     */

    if (type != INET_SERVER && (!NIL_P(arg->local.host) || !NIL_P(arg->local.serv))) {
        arg->local.res = sock_addrinfo(arg->local.host, arg->local.serv, SOCK_STREAM, 0);
    }

    arg->fd = fd = -1;
    for (res = arg->remote.res; res; res = res->ai_next) {
        status = ruby_socket(res->ai_family,res->ai_socktype,res->ai_protocol);
        syscall = "socket(2)";
        fd = status;
        if (fd < 0) {
            continue;
        }
        arg->fd = fd;
        if (type == INET_SERVER) {
#if !defined(_WIN32) && !defined(__CYGWIN__)
            status = 1;
            setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
                       (char*)&status, sizeof(status));
#endif
            status = bind(fd, res->ai_addr, res->ai_addrlen);
            syscall = "bind(2)";
        }
        else {
            if (arg->local.res) {
                status = bind(fd, arg->local.res->ai_addr, arg->local.res->ai_addrlen);
                syscall = "bind(2)";
            }

            if (status >= 0) {
                status = ruby_connect(fd, res->ai_addr, res->ai_addrlen,
                                      (type == INET_SOCKS));
                syscall = "connect(2)";
            }
        }

        if (status < 0) {
            close(fd);
            arg->fd = fd = -1;
            continue;
        } else
            break;
    }
    if (status < 0) {
        rb_sys_fail(syscall);
    }

    arg->fd = -1;

    if (type == INET_SERVER)
        listen(fd, 5);

    /* create new instance */
    return init_sock(arg->sock, fd);
}

static VALUE
init_inetsock(VALUE sock, VALUE remote_host, VALUE remote_serv,
              VALUE local_host, VALUE local_serv, int type)
{
    struct inetsock_arg arg;
    arg.sock = sock;
    arg.remote.host = remote_host;
    arg.remote.serv = remote_serv;
    arg.remote.res = 0;
    arg.local.host = local_host;
    arg.local.serv = local_serv;
    arg.local.res = 0;
    arg.type = type;
    arg.fd = -1;
    return rb_ensure(init_inetsock_internal, (VALUE)&arg,
                     inetsock_cleanup, (VALUE)&arg);
}

/*
 * call-seq:
 *    TCPSocket.new(remote_host, remote_port, local_host=nil, local_port=nil)
 *
 * Opens a TCP connection to +remote_host+ on +remote_port+.  If +local_host+
 * and +local_port+ are specified, then those parameters are used on the local
 * end to establish the connection.
 */
static VALUE
tcp_init(int argc, VALUE *argv, VALUE sock)
{
    VALUE remote_host, remote_serv;
    VALUE local_host, local_serv;

    rb_scan_args(argc, argv, "22", &remote_host, &remote_serv,
                        &local_host, &local_serv);

    return init_inetsock(sock, remote_host, remote_serv,
                        local_host, local_serv, INET_CLIENT);
}

#ifdef SOCKS
static VALUE
socks_init(VALUE sock, VALUE host, VALUE serv)
{
    static init = 0;

    if (init == 0) {
        SOCKSinit("ruby");
        init = 1;
    }

    return init_inetsock(sock, host, serv, Qnil, Qnil, INET_SOCKS);
}

#ifdef SOCKS5
static VALUE
socks_s_close(VALUE sock)
{
    rb_io_t *fptr;

    if (rb_safe_level() >= 4 && !OBJ_TAINTED(sock)) {
        rb_raise(rb_eSecurityError, "Insecure: can't close socket");
    }
    GetOpenFile(sock, fptr);
    shutdown(fptr->fd, 2);
    return rb_io_close(sock);
}
#endif
#endif

struct hostent_arg {
    VALUE host;
    struct addrinfo* addr;
    VALUE (*ipaddr)(struct sockaddr*, size_t);
};

static VALUE
make_hostent_internal(struct hostent_arg *arg)
{
    VALUE host = arg->host;
    struct addrinfo* addr = arg->addr;
    VALUE (*ipaddr)(struct sockaddr*, size_t) = arg->ipaddr;

    struct addrinfo *ai;
    struct hostent *h;
    VALUE ary, names;
    char **pch;
    const char* hostp;
    char hbuf[NI_MAXHOST];

    ary = rb_ary_new();
    if (addr->ai_canonname) {
        hostp = addr->ai_canonname;
    }
    else {
        hostp = host_str(host, hbuf, sizeof(hbuf));
    }
    rb_ary_push(ary, rb_str_new2(hostp));

    if (addr->ai_canonname && (h = gethostbyname(addr->ai_canonname))) {
        names = rb_ary_new();
        if (h->h_aliases != NULL) {
            for (pch = h->h_aliases; *pch; pch++) {
                rb_ary_push(names, rb_str_new2(*pch));
            }
        }
    }
    else {
        names = rb_ary_new2(0);
    }
    rb_ary_push(ary, names);
    rb_ary_push(ary, INT2NUM(addr->ai_family));
    for (ai = addr; ai; ai = ai->ai_next) {
        rb_ary_push(ary, (*ipaddr)(ai->ai_addr, ai->ai_addrlen));
    }

    return ary;
}

static VALUE
make_hostent(VALUE host, struct addrinfo *addr, VALUE (*ipaddr)(struct sockaddr *, size_t))
{
    struct hostent_arg arg;

    arg.host = host;
    arg.addr = addr;
    arg.ipaddr = ipaddr;
    return rb_ensure(make_hostent_internal, (VALUE)&arg,
                     RUBY_METHOD_FUNC(freeaddrinfo), (VALUE)addr);
}

static VALUE
tcp_sockaddr(struct sockaddr *addr, size_t len)
{
    return make_ipaddr(addr);
}

static VALUE
tcp_s_gethostbyname(VALUE obj, VALUE host)
{
    rb_secure(3);
    return make_hostent(host, sock_addrinfo(host, Qnil, SOCK_STREAM, AI_CANONNAME),
                        tcp_sockaddr);
}

static VALUE
tcp_svr_init(int argc, VALUE *argv, VALUE sock)
{
    VALUE arg1, arg2;

    if (rb_scan_args(argc, argv, "11", &arg1, &arg2) == 2)
        return init_inetsock(sock, arg1, arg2, Qnil, Qnil, INET_SERVER);
    else
        return init_inetsock(sock, Qnil, arg1, Qnil, Qnil, INET_SERVER);
}

static void
make_fd_nonblock(int fd)
{
    int flags;
#ifdef F_GETFL
    flags = fcntl(fd, F_GETFL);
    if (flags == -1) {
        rb_sys_fail(0);
    }
#else
    flags = 0;
#endif
    flags |= O_NONBLOCK;
    if (fcntl(fd, F_SETFL, flags) == -1) {
        rb_sys_fail(0);
    }
}

static VALUE
s_accept_nonblock(VALUE klass, rb_io_t *fptr, struct sockaddr *sockaddr, socklen_t *len)
{
    int fd2;

    rb_secure(3);
    rb_io_set_nonblock(fptr);
    fd2 = accept(fptr->fd, (struct sockaddr*)sockaddr, len);
    if (fd2 < 0) {
        rb_sys_fail("accept(2)");
    }
    make_fd_nonblock(fd2);
    return init_sock(rb_obj_alloc(klass), fd2);
}

struct accept_arg {
    int fd;
    struct sockaddr *sockaddr;
    socklen_t *len;
};

static VALUE
accept_blocking(void *data)
{
    struct accept_arg *arg = data;
    return (VALUE)accept(arg->fd, arg->sockaddr, arg->len);
}

static VALUE
s_accept(VALUE klass, int fd, struct sockaddr *sockaddr, socklen_t *len)
{
    int fd2;
    int retry = 0;
    struct accept_arg arg;

    rb_secure(3);
    arg.fd = fd;
    arg.sockaddr = sockaddr;
    arg.len = len;
  retry:
    rb_thread_wait_fd(fd);
    fd2 = BLOCKING_REGION(accept_blocking, &arg);
    if (fd2 < 0) {
        switch (errno) {
          case EMFILE:
          case ENFILE:
            if (retry) break;
            rb_gc();
            retry = 1;
            goto retry;
          default:
            if (!rb_io_wait_readable(fd)) break;
            retry = 0;
            goto retry;
        }
        rb_sys_fail(0);
    }
    if (!klass) return INT2NUM(fd2);
    return init_sock(rb_obj_alloc(klass), fd2);
}

static VALUE
tcp_accept(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_storage from;
    socklen_t fromlen;
 
    GetOpenFile(sock, fptr);
    fromlen = sizeof(from);
    return s_accept(rb_cTCPSocket, fptr->fd,
                    (struct sockaddr*)&from, &fromlen);
}

/*
 * call-seq:
 *      tcpserver.accept_nonblock => tcpsocket
 * 
 * Accepts an incoming connection using accept(2) after
 * O_NONBLOCK is set for the underlying file descriptor.
 * It returns an accepted TCPSocket for the incoming connection.
 * 
 * === Example
 *      require 'socket'
 *      serv = TCPServer.new(2202)
 *      begin # emulate blocking accept
 *        sock = serv.accept_nonblock
 *      rescue Errno::EAGAIN, Errno::EWOULDBLOCK, Errno::ECONNABORTED, Errno::EPROTO, Errno::EINTR
 *        IO.select([serv])
 *        retry
 *      end
 *      # sock is an accepted socket.
 * 
 * Refer to Socket#accept for the exceptions that may be thrown if the call
 * to TCPServer#accept_nonblock fails. 
 *
 * TCPServer#accept_nonblock may raise any error corresponding to accept(2) failure,
 * including Errno::EWOULDBLOCK.
 * 
 * === See
 * * TCPServer#accept
 * * Socket#accept
 */
static VALUE
tcp_accept_nonblock(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_storage from;
    socklen_t fromlen;

    GetOpenFile(sock, fptr);
    fromlen = sizeof(from);
    return s_accept_nonblock(rb_cTCPSocket, fptr,
                             (struct sockaddr *)&from, &fromlen);
}

static VALUE
tcp_sysaccept(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_storage from;
    socklen_t fromlen;

    GetOpenFile(sock, fptr);
    fromlen = sizeof(from);
    return s_accept(0, fptr->fd, (struct sockaddr*)&from, &fromlen);
}

#ifdef HAVE_SYS_UN_H
struct unixsock_arg {
    struct sockaddr_un *sockaddr;
    int fd;
};

static VALUE
unixsock_connect_internal(struct unixsock_arg *arg)
{
    return (VALUE)ruby_connect(arg->fd, (struct sockaddr*)arg->sockaddr,
                               sizeof(*arg->sockaddr), 0);
}

static VALUE
init_unixsock(VALUE sock, VALUE path, int server)
{
    struct sockaddr_un sockaddr;
    int fd, status;
    rb_io_t *fptr;

    SafeStringValue(path);
    fd = ruby_socket(AF_UNIX, SOCK_STREAM, 0);
    if (fd < 0) {
        rb_sys_fail("socket(2)");
    }

    MEMZERO(&sockaddr, struct sockaddr_un, 1);
    sockaddr.sun_family = AF_UNIX;
    if (sizeof(sockaddr.sun_path) <= RSTRING_LEN(path)) {
        rb_raise(rb_eArgError, "too long unix socket path (max: %dbytes)",
            (int)sizeof(sockaddr.sun_path)-1);
    }
    memcpy(sockaddr.sun_path, RSTRING_PTR(path), RSTRING_LEN(path));

    if (server) {
        status = bind(fd, (struct sockaddr*)&sockaddr, sizeof(sockaddr));
    }
    else {
        int prot;
        struct unixsock_arg arg;
        arg.sockaddr = &sockaddr;
        arg.fd = fd;
        status = rb_protect((VALUE(*)(VALUE))unixsock_connect_internal,
                            (VALUE)&arg, &prot);
        if (prot) {
            close(fd);
            rb_jump_tag(prot);
        }
    }

    if (status < 0) {
        close(fd);
        rb_sys_fail(sockaddr.sun_path);
    }

    if (server) listen(fd, 5);

    init_sock(sock, fd);
    if (server) {
        GetOpenFile(sock, fptr);
        fptr->pathv = rb_str_new_frozen(path);
    }

    return sock;
}
#endif

static VALUE
ip_addr(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_storage addr;
    socklen_t len = sizeof addr;

    GetOpenFile(sock, fptr);

    if (getsockname(fptr->fd, (struct sockaddr*)&addr, &len) < 0)
        rb_sys_fail("getsockname(2)");
    return ipaddr((struct sockaddr*)&addr, fptr->mode & FMODE_NOREVLOOKUP);
}

static VALUE
ip_peeraddr(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_storage addr;
    socklen_t len = sizeof addr;

    GetOpenFile(sock, fptr);

    if (getpeername(fptr->fd, (struct sockaddr*)&addr, &len) < 0)
        rb_sys_fail("getpeername(2)");
    return ipaddr((struct sockaddr*)&addr, fptr->mode & FMODE_NOREVLOOKUP);
}

static VALUE
ip_recvfrom(int argc, VALUE *argv, VALUE sock)
{
    return s_recvfrom(sock, argc, argv, RECV_IP);
}

static VALUE
ip_s_getaddress(VALUE obj, VALUE host)
{
    struct sockaddr_storage addr;
    struct addrinfo *res = sock_addrinfo(host, Qnil, SOCK_STREAM, 0);

    /* just take the first one */
    memcpy(&addr, res->ai_addr, res->ai_addrlen);
    freeaddrinfo(res);

    return make_ipaddr((struct sockaddr*)&addr);
}

static VALUE
udp_init(int argc, VALUE *argv, VALUE sock)
{
    VALUE arg;
    int socktype = AF_INET;
    int fd;

    rb_secure(3);
    if (rb_scan_args(argc, argv, "01", &arg) == 1) {
        socktype = NUM2INT(arg);
    }
    fd = ruby_socket(socktype, SOCK_DGRAM, 0);
    if (fd < 0) {
        rb_sys_fail("socket(2) - udp");
    }

    return init_sock(sock, fd);
}

struct udp_arg
{
    struct addrinfo *res;
    int fd;
};

static VALUE
udp_connect_internal(struct udp_arg *arg)
{
    int fd = arg->fd;
    struct addrinfo *res;

    for (res = arg->res; res; res = res->ai_next) {
        if (ruby_connect(fd, res->ai_addr, res->ai_addrlen, 0) >= 0) {
            return Qtrue;
        }
    }
    return Qfalse;
}

static VALUE
udp_connect(VALUE sock, VALUE host, VALUE port)
{
    rb_io_t *fptr;
    struct udp_arg arg;
    VALUE ret;

    rb_secure(3);
    arg.res = sock_addrinfo(host, port, SOCK_DGRAM, 0);
    GetOpenFile(sock, fptr);
    arg.fd = fptr->fd;
    ret = rb_ensure(udp_connect_internal, (VALUE)&arg,
                    RUBY_METHOD_FUNC(freeaddrinfo), (VALUE)arg.res);
    if (!ret) rb_sys_fail("connect(2)");
    return INT2FIX(0);
}

static VALUE
udp_bind(VALUE sock, VALUE host, VALUE port)
{
    rb_io_t *fptr;
    struct addrinfo *res0, *res;

    rb_secure(3);
    res0 = sock_addrinfo(host, port, SOCK_DGRAM, 0);
    GetOpenFile(sock, fptr);
    for (res = res0; res; res = res->ai_next) {
        if (bind(fptr->fd, res->ai_addr, res->ai_addrlen) < 0) {
            continue;
        }
        freeaddrinfo(res0);
        return INT2FIX(0);
    }
    freeaddrinfo(res0);
    rb_sys_fail("bind(2)");
    return INT2FIX(0);
}

static VALUE
udp_send(int argc, VALUE *argv, VALUE sock)
{
    VALUE flags, host, port;
    rb_io_t *fptr;
    int n;
    struct addrinfo *res0, *res;
    struct send_arg arg;

    if (argc == 2 || argc == 3) {
        return bsock_send(argc, argv, sock);
    }
    rb_secure(4);
    rb_scan_args(argc, argv, "4", &arg.mesg, &flags, &host, &port);

    StringValue(arg.mesg);
    res0 = sock_addrinfo(host, port, SOCK_DGRAM, 0);
    GetOpenFile(sock, fptr);
    arg.fd = fptr->fd;
    arg.flags = NUM2INT(flags);
    for (res = res0; res; res = res->ai_next) {
      retry:
        arg.to = res->ai_addr;
        arg.tolen = res->ai_addrlen;
        rb_thread_fd_writable(arg.fd);
        n = (int)BLOCKING_REGION(sendto_blocking, &arg);
        if (n >= 0) {
            freeaddrinfo(res0);
            return INT2FIX(n);
        }
        if (rb_io_wait_writable(fptr->fd)) {
            goto retry;
        }
    }
    freeaddrinfo(res0);
    rb_sys_fail("sendto(2)");
    return INT2FIX(n);
}

/*
 * call-seq:
 *      udpsocket.recvfrom_nonblock(maxlen) => [mesg, sender_inet_addr]
 *      udpsocket.recvfrom_nonblock(maxlen, flags) => [mesg, sender_inet_addr]
 * 
 * Receives up to _maxlen_ bytes from +udpsocket+ using recvfrom(2) after
 * O_NONBLOCK is set for the underlying file descriptor.
 * _flags_ is zero or more of the +MSG_+ options.
 * The first element of the results, _mesg_, is the data received.
 * The second element, _sender_inet_addr_, is an array to represent the sender address.
 *
 * When recvfrom(2) returns 0,
 * Socket#recvfrom_nonblock returns an empty string as data.
 * It means an empty packet.
 * 
 * === Parameters
 * * +maxlen+ - the number of bytes to receive from the socket
 * * +flags+ - zero or more of the +MSG_+ options 
 * 
 * === Example
 *      require 'socket'
 *      s1 = UDPSocket.new
 *      s1.bind("127.0.0.1", 0)
 *      s2 = UDPSocket.new
 *      s2.bind("127.0.0.1", 0)
 *      s2.connect(*s1.addr.values_at(3,1))
 *      s1.connect(*s2.addr.values_at(3,1))
 *      s1.send "aaa", 0
 *      IO.select([s2]) # emulate blocking recvfrom
 *      p s2.recvfrom_nonblock(10)  #=> ["aaa", ["AF_INET", 33302, "localhost.localdomain", "127.0.0.1"]]
 *
 * Refer to Socket#recvfrom for the exceptions that may be thrown if the call
 * to _recvfrom_nonblock_ fails. 
 *
 * UDPSocket#recvfrom_nonblock may raise any error corresponding to recvfrom(2) failure,
 * including Errno::EWOULDBLOCK.
 *
 * === See
 * * Socket#recvfrom
 */
static VALUE
udp_recvfrom_nonblock(int argc, VALUE *argv, VALUE sock)
{
    return s_recvfrom_nonblock(sock, argc, argv, RECV_IP);
}

#ifdef HAVE_SYS_UN_H
static VALUE
unix_init(VALUE sock, VALUE path)
{
    return init_unixsock(sock, path, 0);
}

static const char*
unixpath(struct sockaddr_un *sockaddr, socklen_t len)
{
    if (sockaddr->sun_path < (char*)sockaddr + len)
        return sockaddr->sun_path;
    else
        return "";
}

static VALUE
unix_path(VALUE sock)
{
    rb_io_t *fptr;

    GetOpenFile(sock, fptr);
    if (NIL_P(fptr->pathv)) {
        struct sockaddr_un addr;
        socklen_t len = sizeof(addr);
        if (getsockname(fptr->fd, (struct sockaddr*)&addr, &len) < 0)
            rb_sys_fail(0);
        fptr->pathv = rb_obj_freeze(rb_str_new_cstr(unixpath(&addr, len)));
    }
    return rb_str_dup(fptr->pathv);
}

static VALUE
unix_svr_init(VALUE sock, VALUE path)
{
    return init_unixsock(sock, path, 1);
}

static VALUE
unix_recvfrom(int argc, VALUE *argv, VALUE sock)
{
    return s_recvfrom(sock, argc, argv, RECV_UNIX);
}

#if defined(HAVE_ST_MSG_CONTROL) && defined(SCM_RIGHTS)
#define FD_PASSING_BY_MSG_CONTROL 1
#else
#define FD_PASSING_BY_MSG_CONTROL 0
#endif

#if defined(HAVE_ST_MSG_ACCRIGHTS)
#define FD_PASSING_BY_MSG_ACCRIGHTS 1
#else
#define FD_PASSING_BY_MSG_ACCRIGHTS 0
#endif

struct iomsg_arg {
    int fd;
    struct msghdr msg;
};

static VALUE
sendmsg_blocking(void *data)
{
    struct iomsg_arg *arg = data;
    return sendmsg(arg->fd, &arg->msg, 0);
}

static VALUE
unix_send_io(VALUE sock, VALUE val)
{
#if defined(HAVE_SENDMSG) && (FD_PASSING_BY_MSG_CONTROL || FD_PASSING_BY_MSG_ACCRIGHTS)
    int fd;
    rb_io_t *fptr;
    struct iomsg_arg arg;
    struct iovec vec[1];
    char buf[1];

#if FD_PASSING_BY_MSG_CONTROL
    struct {
        struct cmsghdr hdr;
        char pad[8+sizeof(int)+8];
    } cmsg;
#endif

    if (rb_obj_is_kind_of(val, rb_cIO)) {
        rb_io_t *valfptr;
        GetOpenFile(val, valfptr);
        fd = valfptr->fd;
    }
    else if (FIXNUM_P(val)) {
        fd = FIX2INT(val);
    }
    else {
        rb_raise(rb_eTypeError, "neither IO nor file descriptor");
    }

    GetOpenFile(sock, fptr);

    arg.msg.msg_name = NULL;
    arg.msg.msg_namelen = 0;

    /* Linux and Solaris doesn't work if msg_iov is NULL. */
    buf[0] = '\0';
    vec[0].iov_base = buf;
    vec[0].iov_len = 1;
    arg.msg.msg_iov = vec;
    arg.msg.msg_iovlen = 1;

#if FD_PASSING_BY_MSG_CONTROL
    arg.msg.msg_control = (caddr_t)&cmsg;
    arg.msg.msg_controllen = CMSG_LEN(sizeof(int));
    arg.msg.msg_flags = 0;
    MEMZERO((char*)&cmsg, char, sizeof(cmsg));
    cmsg.hdr.cmsg_len = CMSG_LEN(sizeof(int));
    cmsg.hdr.cmsg_level = SOL_SOCKET;
    cmsg.hdr.cmsg_type = SCM_RIGHTS;
    *(int *)CMSG_DATA(&cmsg.hdr) = fd;
#else
    arg.msg.msg_accrights = (caddr_t)&fd;
    arg.msg.msg_accrightslen = sizeof(fd);
#endif

    arg.fd = fptr->fd;
    rb_thread_fd_writable(arg.fd);
    if ((int)BLOCKING_REGION(sendmsg_blocking, &arg) == -1)
        rb_sys_fail("sendmsg(2)");

    return Qnil;
#else
    rb_notimplement();
    return Qnil;                /* not reached */
#endif
}

static VALUE
recvmsg_blocking(void *data)
{
    struct iomsg_arg *arg = data;
    return recvmsg(arg->fd, &arg->msg, 0);
}

static VALUE
unix_recv_io(int argc, VALUE *argv, VALUE sock)
{
#if defined(HAVE_RECVMSG) && (FD_PASSING_BY_MSG_CONTROL || FD_PASSING_BY_MSG_ACCRIGHTS)
    VALUE klass, mode;
    rb_io_t *fptr;
    struct iomsg_arg arg;
    struct iovec vec[2];
    char buf[1];

    int fd;
#if FD_PASSING_BY_MSG_CONTROL
    struct {
        struct cmsghdr hdr;
        char pad[8+sizeof(int)+8];
    } cmsg;
#endif

    rb_scan_args(argc, argv, "02", &klass, &mode);
    if (argc == 0)
        klass = rb_cIO;
    if (argc <= 1)
        mode = Qnil;

    GetOpenFile(sock, fptr);

    arg.msg.msg_name = NULL;
    arg.msg.msg_namelen = 0;

    vec[0].iov_base = buf;
    vec[0].iov_len = sizeof(buf);
    arg.msg.msg_iov = vec;
    arg.msg.msg_iovlen = 1;

#if FD_PASSING_BY_MSG_CONTROL
    arg.msg.msg_control = (caddr_t)&cmsg;
    arg.msg.msg_controllen = CMSG_SPACE(sizeof(int));
    arg.msg.msg_flags = 0;
    cmsg.hdr.cmsg_len = CMSG_LEN(sizeof(int));
    cmsg.hdr.cmsg_level = SOL_SOCKET;
    cmsg.hdr.cmsg_type = SCM_RIGHTS;
    *(int *)CMSG_DATA(&cmsg.hdr) = -1;
#else
    arg.msg.msg_accrights = (caddr_t)&fd;
    arg.msg.msg_accrightslen = sizeof(fd);
    fd = -1;
#endif

    arg.fd = fptr->fd;
    rb_thread_wait_fd(arg.fd);
    if ((int)BLOCKING_REGION(recvmsg_blocking, &arg) == -1)
        rb_sys_fail("recvmsg(2)");

#if FD_PASSING_BY_MSG_CONTROL
    if (arg.msg.msg_controllen < CMSG_LEN(sizeof(int))) {
        rb_raise(rb_eSocket,
                 "file descriptor was not passed (msg_controllen=%d smaller than CMSG_LEN(sizeof(int))=%d)",
                 (int)arg.msg.msg_controllen, (int)CMSG_LEN(sizeof(int)));
    }
    if (CMSG_SPACE(sizeof(int)) < arg.msg.msg_controllen) {
        rb_raise(rb_eSocket,
                 "file descriptor was not passed (msg_controllen=%d bigger than CMSG_SPACE(sizeof(int))=%d)",
                 (int)arg.msg.msg_controllen, (int)CMSG_SPACE(sizeof(int)));
    }
    if (cmsg.hdr.cmsg_len != CMSG_LEN(sizeof(int))) {
        rb_raise(rb_eSocket,
                 "file descriptor was not passed (cmsg_len=%d, %d expected)",
                 (int)cmsg.hdr.cmsg_len, (int)CMSG_LEN(sizeof(int)));
    }
    if (cmsg.hdr.cmsg_level != SOL_SOCKET) {
        rb_raise(rb_eSocket,
                 "file descriptor was not passed (cmsg_level=%d, %d expected)",
                 cmsg.hdr.cmsg_level, SOL_SOCKET);
    }
    if (cmsg.hdr.cmsg_type != SCM_RIGHTS) {
        rb_raise(rb_eSocket,
                 "file descriptor was not passed (cmsg_type=%d, %d expected)",
                 cmsg.hdr.cmsg_type, SCM_RIGHTS);
    }
#else
    if (arg.msg.msg_accrightslen != sizeof(fd)) {
        rb_raise(rb_eSocket,
                 "file descriptor was not passed (accrightslen) : %d != %d",
                 arg.msg.msg_accrightslen, (int)sizeof(fd));
    }
#endif

#if FD_PASSING_BY_MSG_CONTROL
    fd = *(int *)CMSG_DATA(&cmsg.hdr);
#endif

    if (klass == Qnil)
        return INT2FIX(fd);
    else {
        ID for_fd;
        int ff_argc;
        VALUE ff_argv[2];
        CONST_ID(for_fd, "for_fd");
        ff_argc = mode == Qnil ? 1 : 2;
        ff_argv[0] = INT2FIX(fd);
        ff_argv[1] = mode;
        return rb_funcall2(klass, for_fd, ff_argc, ff_argv);
    }
#else
    rb_notimplement();
    return Qnil;                /* not reached */
#endif
}

static VALUE
unix_accept(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_un from;
    socklen_t fromlen;

    GetOpenFile(sock, fptr);
    fromlen = sizeof(struct sockaddr_un);
    return s_accept(rb_cUNIXSocket, fptr->fd,
                    (struct sockaddr*)&from, &fromlen);
}

/*
 * call-seq:
 *      unixserver.accept_nonblock => unixsocket
 * 
 * Accepts an incoming connection using accept(2) after
 * O_NONBLOCK is set for the underlying file descriptor.
 * It returns an accepted UNIXSocket for the incoming connection.
 * 
 * === Example
 *      require 'socket'
 *      serv = UNIXServer.new("/tmp/sock")
 *      begin # emulate blocking accept
 *        sock = serv.accept_nonblock
 *      rescue Errno::EAGAIN, Errno::EWOULDBLOCK, Errno::ECONNABORTED, Errno::EPROTO, Errno::EINTR
 *        IO.select([serv])
 *        retry
 *      end
 *      # sock is an accepted socket.
 * 
 * Refer to Socket#accept for the exceptions that may be thrown if the call
 * to UNIXServer#accept_nonblock fails. 
 *
 * UNIXServer#accept_nonblock may raise any error corresponding to accept(2) failure,
 * including Errno::EWOULDBLOCK.
 * 
 * === See
 * * UNIXServer#accept
 * * Socket#accept
 */
static VALUE
unix_accept_nonblock(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_un from;
    socklen_t fromlen;

    GetOpenFile(sock, fptr);
    fromlen = sizeof(from);
    return s_accept_nonblock(rb_cUNIXSocket, fptr,
                             (struct sockaddr *)&from, &fromlen);
}

static VALUE
unix_sysaccept(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_un from;
    socklen_t fromlen;

    GetOpenFile(sock, fptr);
    fromlen = sizeof(struct sockaddr_un);
    return s_accept(0, fptr->fd, (struct sockaddr*)&from, &fromlen);
}

#ifdef HAVE_SYS_UN_H
static VALUE
unixaddr(struct sockaddr_un *sockaddr, socklen_t len)
{
    return rb_assoc_new(rb_str_new2("AF_UNIX"),
                        rb_str_new2(unixpath(sockaddr, len)));
}
#endif

static VALUE
unix_addr(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_un addr;
    socklen_t len = sizeof addr;

    GetOpenFile(sock, fptr);

    if (getsockname(fptr->fd, (struct sockaddr*)&addr, &len) < 0)
        rb_sys_fail("getsockname(2)");
    return unixaddr(&addr, len);
}

static VALUE
unix_peeraddr(VALUE sock)
{
    rb_io_t *fptr;
    struct sockaddr_un addr;
    socklen_t len = sizeof addr;

    GetOpenFile(sock, fptr);

    if (getpeername(fptr->fd, (struct sockaddr*)&addr, &len) < 0)
        rb_sys_fail("getpeername(2)");
    return unixaddr(&addr, len);
}
#endif

static void
setup_domain_and_type(VALUE domain, int *dv, VALUE type, int *tv)
{
    VALUE tmp;
    char *ptr;

    tmp = rb_check_string_type(domain);
    if (!NIL_P(tmp)) {
        domain = tmp;
        rb_check_safe_obj(domain);
        ptr = RSTRING_PTR(domain);
        if (strcmp(ptr, "AF_INET") == 0)
            *dv = AF_INET;
#ifdef AF_UNIX
        else if (strcmp(ptr, "AF_UNIX") == 0)
            *dv = AF_UNIX;
#endif
#ifdef AF_ISO
        else if (strcmp(ptr, "AF_ISO") == 0)
            *dv = AF_ISO;
#endif
#ifdef AF_NS
        else if (strcmp(ptr, "AF_NS") == 0)
            *dv = AF_NS;
#endif
#ifdef AF_IMPLINK
        else if (strcmp(ptr, "AF_IMPLINK") == 0)
            *dv = AF_IMPLINK;
#endif
#ifdef PF_INET
        else if (strcmp(ptr, "PF_INET") == 0)
            *dv = PF_INET;
#endif
#ifdef PF_UNIX
        else if (strcmp(ptr, "PF_UNIX") == 0)
            *dv = PF_UNIX;
#endif
#ifdef PF_IMPLINK
        else if (strcmp(ptr, "PF_IMPLINK") == 0)
            *dv = PF_IMPLINK;
        else if (strcmp(ptr, "AF_IMPLINK") == 0)
            *dv = AF_IMPLINK;
#endif
#ifdef PF_AX25
        else if (strcmp(ptr, "PF_AX25") == 0)
            *dv = PF_AX25;
#endif
#ifdef PF_IPX
        else if (strcmp(ptr, "PF_IPX") == 0)
            *dv = PF_IPX;
#endif
        else
            rb_raise(rb_eSocket, "unknown socket domain %s", ptr);
    }
    else {
        *dv = NUM2INT(domain);
    }
    tmp = rb_check_string_type(type);
    if (!NIL_P(tmp)) {
        type = tmp;
        rb_check_safe_obj(type);
        ptr = RSTRING_PTR(type);
        if (strcmp(ptr, "SOCK_STREAM") == 0)
            *tv = SOCK_STREAM;
        else if (strcmp(ptr, "SOCK_DGRAM") == 0)
            *tv = SOCK_DGRAM;
#ifdef SOCK_RAW
        else if (strcmp(ptr, "SOCK_RAW") == 0)
            *tv = SOCK_RAW;
#endif
#ifdef SOCK_SEQPACKET
        else if (strcmp(ptr, "SOCK_SEQPACKET") == 0)
            *tv = SOCK_SEQPACKET;
#endif
#ifdef SOCK_RDM
        else if (strcmp(ptr, "SOCK_RDM") == 0)
            *tv = SOCK_RDM;
#endif
#ifdef SOCK_PACKET
        else if (strcmp(ptr, "SOCK_PACKET") == 0)
            *tv = SOCK_PACKET;
#endif
        else
            rb_raise(rb_eSocket, "unknown socket type %s", ptr);
    }
    else {
        *tv = NUM2INT(type);
    }
}

static VALUE
sock_initialize(VALUE sock, VALUE domain, VALUE type, VALUE protocol)
{
    int fd;
    int d, t;

    rb_secure(3);
    setup_domain_and_type(domain, &d, type, &t);
    fd = ruby_socket(d, t, NUM2INT(protocol));
    if (fd < 0) rb_sys_fail("socket(2)");

    return init_sock(sock, fd);
}

static VALUE
sock_s_socketpair(VALUE klass, VALUE domain, VALUE type, VALUE protocol)
{
#if defined HAVE_SOCKETPAIR
    int d, t, p, sp[2];
    int ret;

    setup_domain_and_type(domain, &d, type, &t);
    p = NUM2INT(protocol);
    ret = socketpair(d, t, p, sp);
    if (ret < 0 && (errno == EMFILE || errno == ENFILE)) {
        rb_gc();
        ret = socketpair(d, t, p, sp);
    }
    if (ret < 0) {
        rb_sys_fail("socketpair(2)");
    }

    return rb_assoc_new(init_sock(rb_obj_alloc(klass), sp[0]),
                        init_sock(rb_obj_alloc(klass), sp[1]));
#else
    rb_notimplement();
#endif
}

#ifdef HAVE_SYS_UN_H
static VALUE
unix_s_socketpair(int argc, VALUE *argv, VALUE klass)
{
    VALUE domain, type, protocol;
    domain = INT2FIX(PF_UNIX);

    rb_scan_args(argc, argv, "02", &type, &protocol);
    if (argc == 0)
        type = INT2FIX(SOCK_STREAM);
    if (argc <= 1)
        protocol = INT2FIX(0);

    return sock_s_socketpair(klass, domain, type, protocol);
}
#endif

/*
 * call-seq:
 *      socket.connect(server_sockaddr) => 0
 * 
 * Requests a connection to be made on the given +server_sockaddr+. Returns 0 if
 * successful, otherwise an exception is raised.
 *  
 * === Parameter
 * * +server_sockaddr+ - the +struct+ sockaddr contained in a string
 * 
 * === Example:
 *      # Pull down Google's web page
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
 *      sockaddr = Socket.pack_sockaddr_in( 80, 'www.google.com' )
 *      socket.connect( sockaddr )
 *      socket.write( "GET / HTTP/1.0\r\n\r\n" )
 *      results = socket.read 
 * 
 * === Unix-based Exceptions
 * On unix-based systems the following system exceptions may be raised if 
 * the call to _connect_ fails:
 * * Errno::EACCES - search permission is denied for a component of the prefix
 *   path or write access to the +socket+ is denided
 * * Errno::EADDRINUSE - the _sockaddr_ is already in use
 * * Errno::EADDRNOTAVAIL - the specified _sockaddr_ is not available from the
 *   local machine
 * * Errno::EAFNOSUPPORT - the specified _sockaddr_ is not a valid address for 
 *   the address family of the specified +socket+
 * * Errno::EALREADY - a connection is already in progress for the specified
 *   socket
 * * Errno::EBADF - the +socket+ is not a valid file descriptor
 * * Errno::ECONNREFUSED - the target _sockaddr_ was not listening for connections
 *   refused the connection request
 * * Errno::ECONNRESET - the remote host reset the connection request
 * * Errno::EFAULT - the _sockaddr_ cannot be accessed
 * * Errno::EHOSTUNREACH - the destination host cannot be reached (probably 
 *   because the host is down or a remote router cannot reach it)
 * * Errno::EINPROGRESS - the O_NONBLOCK is set for the +socket+ and the
 *   connection cnanot be immediately established; the connection will be
 *   established asynchronously
 * * Errno::EINTR - the attempt to establish the connection was interrupted by
 *   delivery of a signal that was caught; the connection will be established
 *   asynchronously
 * * Errno::EISCONN - the specified +socket+ is already connected
 * * Errno::EINVAL - the address length used for the _sockaddr_ is not a valid
 *   length for the address family or there is an invalid family in _sockaddr_ 
 * * Errno::ENAMETOOLONG - the pathname resolved had a length which exceeded
 *   PATH_MAX
 * * Errno::ENETDOWN - the local interface used to reach the destination is down
 * * Errno::ENETUNREACH - no route to the network is present
 * * Errno::ENOBUFS - no buffer space is available
 * * Errno::ENOSR - there were insufficient STREAMS resources available to 
 *   complete the operation
 * * Errno::ENOTSOCK - the +socket+ argument does not refer to a socket
 * * Errno::EOPNOTSUPP - the calling +socket+ is listening and cannot be connected
 * * Errno::EPROTOTYPE - the _sockaddr_ has a different type than the socket 
 *   bound to the specified peer address
 * * Errno::ETIMEDOUT - the attempt to connect time out before a connection
 *   was made.
 * 
 * On unix-based systems if the address family of the calling +socket+ is
 * AF_UNIX the follow exceptions may be raised if the call to _connect_
 * fails:
 * * Errno::EIO - an i/o error occured while reading from or writing to the 
 *   file system
 * * Errno::ELOOP - too many symbolic links were encountered in translating
 *   the pathname in _sockaddr_
 * * Errno::ENAMETOOLLONG - a component of a pathname exceeded NAME_MAX 
 *   characters, or an entired pathname exceeded PATH_MAX characters
 * * Errno::ENOENT - a component of the pathname does not name an existing file
 *   or the pathname is an empty string
 * * Errno::ENOTDIR - a component of the path prefix of the pathname in _sockaddr_
 *   is not a directory 
 * 
 * === Windows Exceptions
 * On Windows systems the following system exceptions may be raised if 
 * the call to _connect_ fails:
 * * Errno::ENETDOWN - the network is down
 * * Errno::EADDRINUSE - the socket's local address is already in use
 * * Errno::EINTR - the socket was cancelled
 * * Errno::EINPROGRESS - a blocking socket is in progress or the service provider
 *   is still processing a callback function. Or a nonblocking connect call is 
 *   in progress on the +socket+.
 * * Errno::EALREADY - see Errno::EINVAL
 * * Errno::EADDRNOTAVAIL - the remote address is not a valid address, such as 
 *   ADDR_ANY TODO check ADDRANY TO INADDR_ANY
 * * Errno::EAFNOSUPPORT - addresses in the specified family cannot be used with
 *   with this +socket+
 * * Errno::ECONNREFUSED - the target _sockaddr_ was not listening for connections
 *   refused the connection request
 * * Errno::EFAULT - the socket's internal address or address length parameter
 *   is too small or is not a valid part of the user space address
 * * Errno::EINVAL - the +socket+ is a listening socket
 * * Errno::EISCONN - the +socket+ is already connected
 * * Errno::ENETUNREACH - the network cannot be reached from this host at this time
 * * Errno::EHOSTUNREACH - no route to the network is present
 * * Errno::ENOBUFS - no buffer space is available
 * * Errno::ENOTSOCK - the +socket+ argument does not refer to a socket
 * * Errno::ETIMEDOUT - the attempt to connect time out before a connection
 *   was made.
 * * Errno::EWOULDBLOCK - the socket is marked as nonblocking and the 
 *   connection cannot be completed immediately
 * * Errno::EACCES - the attempt to connect the datagram socket to the 
 *   broadcast address failed
 * 
 * === See
 * * connect manual pages on unix-based systems
 * * connect function in Microsoft's Winsock functions reference
 */
static VALUE
sock_connect(VALUE sock, VALUE addr)
{
    rb_io_t *fptr;
    int fd, n;

    StringValue(addr);
    addr = rb_str_new4(addr);
    GetOpenFile(sock, fptr);
    fd = fptr->fd;
    n = ruby_connect(fd, (struct sockaddr*)RSTRING_PTR(addr), RSTRING_LEN(addr), 0);
    if (n < 0) {
        rb_sys_fail("connect(2)");
    }

    return INT2FIX(n);
}

/*
 * call-seq:
 *      socket.connect_nonblock(server_sockaddr) => 0
 * 
 * Requests a connection to be made on the given +server_sockaddr+ after
 * O_NONBLOCK is set for the underlying file descriptor.
 * Returns 0 if successful, otherwise an exception is raised.
 *  
 * === Parameter
 * * +server_sockaddr+ - the +struct+ sockaddr contained in a string
 * 
 * === Example:
 *      # Pull down Google's web page
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new(AF_INET, SOCK_STREAM, 0)
 *      sockaddr = Socket.sockaddr_in(80, 'www.google.com')
 *      begin # emulate blocking connect
 *        socket.connect_nonblock(sockaddr)
 *      rescue Errno::EINPROGRESS
 *        IO.select(nil, [socket])
 *        begin
 *          socket.connect_nonblock(sockaddr)
 *        rescue Errno::EISCONN
 *        end
 *      end
 *      socket.write("GET / HTTP/1.0\r\n\r\n")
 *      results = socket.read 
 * 
 * Refer to Socket#connect for the exceptions that may be thrown if the call
 * to _connect_nonblock_ fails. 
 *
 * Socket#connect_nonblock may raise any error corresponding to connect(2) failure,
 * including Errno::EINPROGRESS.
 *
 * === See
 * * Socket#connect
 */
static VALUE
sock_connect_nonblock(VALUE sock, VALUE addr)
{
    rb_io_t *fptr;
    int n;

    StringValue(addr);
    addr = rb_str_new4(addr);
    GetOpenFile(sock, fptr);
    rb_io_set_nonblock(fptr);
    n = connect(fptr->fd, (struct sockaddr*)RSTRING_PTR(addr), RSTRING_LEN(addr));
    if (n < 0) {
        rb_sys_fail("connect(2)");
    }

    return INT2FIX(n);
}

/*
 * call-seq:
 *      socket.bind(server_sockaddr) => 0
 * 
 * Binds to the given +struct+ sockaddr.
 * 
 * === Parameter
 * * +server_sockaddr+ - the +struct+ sockaddr contained in a string
 *
 * === Example
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
 *      sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
 *      socket.bind( sockaddr )
 *  
 * === Unix-based Exceptions
 * On unix-based based systems the following system exceptions may be raised if 
 * the call to _bind_ fails:
 * * Errno::EACCES - the specified _sockaddr_ is protected and the current
 *   user does not have permission to bind to it
 * * Errno::EADDRINUSE - the specified _sockaddr_ is already in use
 * * Errno::EADDRNOTAVAIL - the specified _sockaddr_ is not available from the
 *   local machine
 * * Errno::EAFNOSUPPORT - the specified _sockaddr_ isnot a valid address for
 *   the family of the calling +socket+
 * * Errno::EBADF - the _sockaddr_ specified is not a valid file descriptor
 * * Errno::EFAULT - the _sockaddr_ argument cannot be accessed
 * * Errno::EINVAL - the +socket+ is already bound to an address, and the 
 *   protocol does not support binding to the new _sockaddr_ or the +socket+
 *   has been shut down.
 * * Errno::EINVAL - the address length is not a valid length for the address
 *   family
 * * Errno::ENAMETOOLONG - the pathname resolved had a length which exceeded
 *   PATH_MAX
 * * Errno::ENOBUFS - no buffer space is available
 * * Errno::ENOSR - there were insufficient STREAMS resources available to 
 *   complete the operation
 * * Errno::ENOTSOCK - the +socket+ does not refer to a socket
 * * Errno::EOPNOTSUPP - the socket type of the +socket+ does not support 
 *   binding to an address
 * 
 * On unix-based based systems if the address family of the calling +socket+ is
 * Socket::AF_UNIX the follow exceptions may be raised if the call to _bind_
 * fails:
 * * Errno::EACCES - search permission is denied for a component of the prefix
 *   path or write access to the +socket+ is denided
 * * Errno::EDESTADDRREQ - the _sockaddr_ argument is a null pointer
 * * Errno::EISDIR - same as Errno::EDESTADDRREQ
 * * Errno::EIO - an i/o error occurred
 * * Errno::ELOOP - too many symbolic links were encountered in translating
 *   the pathname in _sockaddr_
 * * Errno::ENAMETOOLLONG - a component of a pathname exceeded NAME_MAX 
 *   characters, or an entired pathname exceeded PATH_MAX characters
 * * Errno::ENOENT - a component of the pathname does not name an existing file
 *   or the pathname is an empty string
 * * Errno::ENOTDIR - a component of the path prefix of the pathname in _sockaddr_
 *   is not a directory
 * * Errno::EROFS - the name would reside on a read only filesystem
 * 
 * === Windows Exceptions
 * On Windows systems the following system exceptions may be raised if 
 * the call to _bind_ fails:
 * * Errno::ENETDOWN-- the network is down
 * * Errno::EACCES - the attempt to connect the datagram socket to the 
 *   broadcast address failed
 * * Errno::EADDRINUSE - the socket's local address is already in use
 * * Errno::EADDRNOTAVAIL - the specified address is not a valid address for this
 *   computer
 * * Errno::EFAULT - the socket's internal address or address length parameter
 *   is too small or is not a valid part of the user space addressed
 * * Errno::EINVAL - the +socket+ is already bound to an address
 * * Errno::ENOBUFS - no buffer space is available
 * * Errno::ENOTSOCK - the +socket+ argument does not refer to a socket
 * 
 * === See
 * * bind manual pages on unix-based systems
 * * bind function in Microsoft's Winsock functions reference
 */ 
static VALUE
sock_bind(VALUE sock, VALUE addr)
{
    rb_io_t *fptr;

    StringValue(addr);
    GetOpenFile(sock, fptr);
    if (bind(fptr->fd, (struct sockaddr*)RSTRING_PTR(addr), RSTRING_LEN(addr)) < 0)
        rb_sys_fail("bind(2)");

    return INT2FIX(0);
}

/*
 * call-seq:
 *      socket.listen( int ) => 0
 * 
 * Listens for connections, using the specified +int+ as the backlog. A call
 * to _listen_ only applies if the +socket+ is of type SOCK_STREAM or 
 * SOCK_SEQPACKET.
 * 
 * === Parameter
 * * +backlog+ - the maximum length of the queue for pending connections.
 * 
 * === Example 1
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
 *      sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
 *      socket.bind( sockaddr )
 *      socket.listen( 5 )
 * 
 * === Example 2 (listening on an arbitary port, unix-based systems only):
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
 *      socket.listen( 1 )
 * 
 * === Unix-based Exceptions
 * On unix based systems the above will work because a new +sockaddr+ struct
 * is created on the address ADDR_ANY, for an arbitrary port number as handed
 * off by the kernel. It will not work on Windows, because Windows requires that
 * the +socket+ is bound by calling _bind_ before it can _listen_.
 * 
 * If the _backlog_ amount exceeds the implementation-dependent maximum
 * queue length, the implementation's maximum queue length will be used.
 * 
 * On unix-based based systems the following system exceptions may be raised if the
 * call to _listen_ fails:
 * * Errno::EBADF - the _socket_ argument is not a valid file descriptor
 * * Errno::EDESTADDRREQ - the _socket_ is not bound to a local address, and 
 *   the protocol does not support listening on an unbound socket
 * * Errno::EINVAL - the _socket_ is already connected
 * * Errno::ENOTSOCK - the _socket_ argument does not refer to a socket
 * * Errno::EOPNOTSUPP - the _socket_ protocol does not support listen
 * * Errno::EACCES - the calling process does not have approriate privileges
 * * Errno::EINVAL - the _socket_ has been shut down
 * * Errno::ENOBUFS - insufficient resources are available in the system to 
 *   complete the call
 * 
 * === Windows Exceptions
 * On Windows systems the following system exceptions may be raised if 
 * the call to _listen_ fails:
 * * Errno::ENETDOWN - the network is down
 * * Errno::EADDRINUSE - the socket's local address is already in use. This 
 *   usually occurs during the execution of _bind_ but could be delayed
 *   if the call to _bind_ was to a partially wildcard address (involving
 *   ADDR_ANY) and if a specific address needs to be commmitted at the 
 *   time of the call to _listen_
 * * Errno::EINPROGRESS - a Windows Sockets 1.1 call is in progress or the
 *   service provider is still processing a callback function
 * * Errno::EINVAL - the +socket+ has not been bound with a call to _bind_.
 * * Errno::EISCONN - the +socket+ is already connected
 * * Errno::EMFILE - no more socket descriptors are available
 * * Errno::ENOBUFS - no buffer space is available
 * * Errno::ENOTSOC - +socket+ is not a socket
 * * Errno::EOPNOTSUPP - the referenced +socket+ is not a type that supports
 *   the _listen_ method
 * 
 * === See
 * * listen manual pages on unix-based systems
 * * listen function in Microsoft's Winsock functions reference
 */
static VALUE
sock_listen(VALUE sock, VALUE log)
{
    rb_io_t *fptr;
    int backlog;

    rb_secure(4);
    backlog = NUM2INT(log);
    GetOpenFile(sock, fptr);
    if (listen(fptr->fd, backlog) < 0)
        rb_sys_fail("listen(2)");

    return INT2FIX(0);
}

/*
 * call-seq:
 *      socket.recvfrom(maxlen) => [mesg, sender_sockaddr]
 *      socket.recvfrom(maxlen, flags) => [mesg, sender_sockaddr]
 * 
 * Receives up to _maxlen_ bytes from +socket+. _flags_ is zero or more
 * of the +MSG_+ options. The first element of the results, _mesg_, is the data
 * received. The second element, _sender_sockaddr_, contains protocol-specific information
 * on the sender.
 * 
 * === Parameters
 * * +maxlen+ - the number of bytes to receive from the socket
 * * +flags+ - zero or more of the +MSG_+ options 
 * 
 * === Example
 *      # In one file, start this first
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
 *      sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
 *      socket.bind( sockaddr )
 *      socket.listen( 5 )
 *      client, client_sockaddr = socket.accept
 *      data = client.recvfrom( 20 )[0].chomp
 *      puts "I only received 20 bytes '#{data}'"
 *      sleep 1
 *      socket.close
 * 
 *      # In another file, start this second
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
 *      sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
 *      socket.connect( sockaddr )
 *      socket.puts "Watch this get cut short!"
 *      socket.close 
 * 
 * === Unix-based Exceptions
 * On unix-based based systems the following system exceptions may be raised if the
 * call to _recvfrom_ fails:
 * * Errno::EAGAIN - the +socket+ file descriptor is marked as O_NONBLOCK and no
 *   data is waiting to be received; or MSG_OOB is set and no out-of-band data
 *   is available and either the +socket+ file descriptor is marked as 
 *   O_NONBLOCK or the +socket+ does not support blocking to wait for 
 *   out-of-band-data
 * * Errno::EWOULDBLOCK - see Errno::EAGAIN
 * * Errno::EBADF - the +socket+ is not a valid file descriptor
 * * Errno::ECONNRESET - a connection was forcibly closed by a peer
 * * Errno::EFAULT - the socket's internal buffer, address or address length 
 *   cannot be accessed or written
 * * Errno::EINTR - a signal interupted _recvfrom_ before any data was available
 * * Errno::EINVAL - the MSG_OOB flag is set and no out-of-band data is available
 * * Errno::EIO - an i/o error occurred while reading from or writing to the 
 *   filesystem
 * * Errno::ENOBUFS - insufficient resources were available in the system to 
 *   perform the operation
 * * Errno::ENOMEM - insufficient memory was available to fulfill the request
 * * Errno::ENOSR - there were insufficient STREAMS resources available to 
 *   complete the operation
 * * Errno::ENOTCONN - a receive is attempted on a connection-mode socket that
 *   is not connected
 * * Errno::ENOTSOCK - the +socket+ does not refer to a socket
 * * Errno::EOPNOTSUPP - the specified flags are not supported for this socket type
 * * Errno::ETIMEDOUT - the connection timed out during connection establishment
 *   or due to a transmission timeout on an active connection
 * 
 * === Windows Exceptions
 * On Windows systems the following system exceptions may be raised if 
 * the call to _recvfrom_ fails:
 * * Errno::ENETDOWN - the network is down
 * * Errno::EFAULT - the internal buffer and from parameters on +socket+ are not
 *   part of the user address space, or the internal fromlen parameter is
 *   too small to accomodate the peer address
 * * Errno::EINTR - the (blocking) call was cancelled by an internal call to
 *   the WinSock function WSACancelBlockingCall
 * * Errno::EINPROGRESS - a blocking Windows Sockets 1.1 call is in progress or 
 *   the service provider is still processing a callback function
 * * Errno::EINVAL - +socket+ has not been bound with a call to _bind_, or an
 *   unknown flag was specified, or MSG_OOB was specified for a socket with
 *   SO_OOBINLINE enabled, or (for byte stream-style sockets only) the internal
 *   len parameter on +socket+ was zero or negative
 * * Errno::EISCONN - +socket+ is already connected. The call to _recvfrom_ is
 *   not permitted with a connected socket on a socket that is connetion 
 *   oriented or connectionless.
 * * Errno::ENETRESET - the connection has been broken due to the keep-alive 
 *   activity detecting a failure while the operation was in progress.
 * * Errno::EOPNOTSUPP - MSG_OOB was specified, but +socket+ is not stream-style
 *   such as type SOCK_STREAM. OOB data is not supported in the communication
 *   domain associated with +socket+, or +socket+ is unidirectional and 
 *   supports only send operations
 * * Errno::ESHUTDOWN - +socket+ has been shutdown. It is not possible to 
 *   call _recvfrom_ on a socket after _shutdown_ has been invoked.
 * * Errno::EWOULDBLOCK - +socket+ is marked as nonblocking and a  call to 
 *   _recvfrom_ would block.
 * * Errno::EMSGSIZE - the message was too large to fit into the specified buffer
 *   and was truncated.
 * * Errno::ETIMEDOUT - the connection has been dropped, because of a network
 *   failure or because the system on the other end went down without
 *   notice
 * * Errno::ECONNRESET - the virtual circuit was reset by the remote side 
 *   executing a hard or abortive close. The application should close the
 *   socket; it is no longer usable. On a UDP-datagram socket this error
 *   indicates a previous send operation resulted in an ICMP Port Unreachable
 *   message.
 */
static VALUE
sock_recvfrom(int argc, VALUE *argv, VALUE sock)
{
    return s_recvfrom(sock, argc, argv, RECV_SOCKET);
}

/*
 * call-seq:
 *      socket.recvfrom_nonblock(maxlen) => [mesg, sender_sockaddr]
 *      socket.recvfrom_nonblock(maxlen, flags) => [mesg, sender_sockaddr]
 * 
 * Receives up to _maxlen_ bytes from +socket+ using recvfrom(2) after
 * O_NONBLOCK is set for the underlying file descriptor.
 * _flags_ is zero or more of the +MSG_+ options.
 * The first element of the results, _mesg_, is the data received.
 * The second element, _sender_sockaddr_, contains protocol-specific information
 * on the sender.
 *
 * When recvfrom(2) returns 0, Socket#recvfrom_nonblock returns
 * an empty string as data.
 * The meaning depends on the socket: EOF on TCP, empty packet on UDP, etc.
 * 
 * === Parameters
 * * +maxlen+ - the number of bytes to receive from the socket
 * * +flags+ - zero or more of the +MSG_+ options 
 * 
 * === Example
 *      # In one file, start this first
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new(AF_INET, SOCK_STREAM, 0)
 *      sockaddr = Socket.sockaddr_in(2200, 'localhost')
 *      socket.bind(sockaddr)
 *      socket.listen(5)
 *      client, client_sockaddr = socket.accept
 *      begin # emulate blocking recvfrom
 *        pair = client.recvfrom_nonblock(20)
 *      rescue Errno::EAGAIN, Errno::EWOULDBLOCK
 *        IO.select([client])
 *        retry
 *      end
 *      data = pair[0].chomp
 *      puts "I only received 20 bytes '#{data}'"
 *      sleep 1
 *      socket.close
 * 
 *      # In another file, start this second
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new(AF_INET, SOCK_STREAM, 0)
 *      sockaddr = Socket.sockaddr_in(2200, 'localhost')
 *      socket.connect(sockaddr)
 *      socket.puts "Watch this get cut short!"
 *      socket.close 
 * 
 * Refer to Socket#recvfrom for the exceptions that may be thrown if the call
 * to _recvfrom_nonblock_ fails. 
 *
 * Socket#recvfrom_nonblock may raise any error corresponding to recvfrom(2) failure,
 * including Errno::EWOULDBLOCK.
 *
 * === See
 * * Socket#recvfrom
 */
static VALUE
sock_recvfrom_nonblock(int argc, VALUE *argv, VALUE sock)
{
    return s_recvfrom_nonblock(sock, argc, argv, RECV_SOCKET);
}

static VALUE
sock_accept(VALUE sock)
{
    rb_io_t *fptr;
    VALUE sock2;
    char buf[1024];
    socklen_t len = sizeof buf;

    GetOpenFile(sock, fptr);
    sock2 = s_accept(rb_cSocket,fptr->fd,(struct sockaddr*)buf,&len);

    return rb_assoc_new(sock2, rb_str_new(buf, len));
}

/*
 * call-seq:
 *      socket.accept_nonblock => [client_socket, client_sockaddr]
 * 
 * Accepts an incoming connection using accept(2) after
 * O_NONBLOCK is set for the underlying file descriptor.
 * It returns an array containg the accpeted socket
 * for the incoming connection, _client_socket_,
 * and a string that contains the +struct+ sockaddr information
 * about the caller, _client_sockaddr_.
 * 
 * === Example
 *      # In one script, start this first
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new(AF_INET, SOCK_STREAM, 0)
 *      sockaddr = Socket.sockaddr_in(2200, 'localhost')
 *      socket.bind(sockaddr)
 *      socket.listen(5)
 *      begin # emulate blocking accept
 *        client_socket, client_sockaddr = socket.accept_nonblock
 *      rescue Errno::EAGAIN, Errno::EWOULDBLOCK, Errno::ECONNABORTED, Errno::EPROTO, Errno::EINTR
 *        IO.select([socket])
 *        retry
 *      end
 *      puts "The client said, '#{client_socket.readline.chomp}'"
 *      client_socket.puts "Hello from script one!"
 *      socket.close
 * 
 *      # In another script, start this second
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new(AF_INET, SOCK_STREAM, 0)
 *      sockaddr = Socket.sockaddr_in(2200, 'localhost')
 *      socket.connect(sockaddr)
 *      socket.puts "Hello from script 2." 
 *      puts "The server said, '#{socket.readline.chomp}'"
 *      socket.close
 * 
 * Refer to Socket#accept for the exceptions that may be thrown if the call
 * to _accept_nonblock_ fails. 
 *
 * Socket#accept_nonblock may raise any error corresponding to accept(2) failure,
 * including Errno::EWOULDBLOCK.
 * 
 * === See
 * * Socket#accept
 */
static VALUE
sock_accept_nonblock(VALUE sock)
{
    rb_io_t *fptr;
    VALUE sock2;
    char buf[1024];
    socklen_t len = sizeof buf;

    GetOpenFile(sock, fptr);
    sock2 = s_accept_nonblock(rb_cSocket, fptr, (struct sockaddr *)buf, &len);
    return rb_assoc_new(sock2, rb_str_new(buf, len));
}

/*
 * call-seq:
 *      socket.sysaccept => [client_socket_fd, client_sockaddr]
 * 
 * Accepts an incoming connection returnings an array containg the (integer)
 * file descriptor for the incoming connection, _client_socket_fd_,
 * and a string that contains the +struct+ sockaddr information
 * about the caller, _client_sockaddr_.
 * 
 * === Example
 *      # In one script, start this first
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
 *      sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
 *      socket.bind( sockaddr )
 *      socket.listen( 5 )
 *      client_fd, client_sockaddr = socket.sysaccept
 *      client_socket = Socket.for_fd( client_fd )
 *      puts "The client said, '#{client_socket.readline.chomp}'"
 *      client_socket.puts "Hello from script one!"
 *      socket.close
 * 
 *      # In another script, start this second
 *      require 'socket'
 *      include Socket::Constants
 *      socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
 *      sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
 *      socket.connect( sockaddr )
 *      socket.puts "Hello from script 2." 
 *      puts "The server said, '#{socket.readline.chomp}'"
 *      socket.close
 * 
 * Refer to Socket#accept for the exceptions that may be thrown if the call
 * to _sysaccept_ fails. 
 * 
 * === See
 * * Socket#accept
 */
static VALUE
sock_sysaccept(VALUE sock)
{
    rb_io_t *fptr;
    VALUE sock2;
    char buf[1024];
    socklen_t len = sizeof buf;

    GetOpenFile(sock, fptr);
    sock2 = s_accept(0,fptr->fd,(struct sockaddr*)buf,&len);

    return rb_assoc_new(sock2, rb_str_new(buf, len));
}

#ifdef HAVE_GETHOSTNAME
static VALUE
sock_gethostname(VALUE obj)
{
    char buf[1024];

    rb_secure(3);
    if (gethostname(buf, (int)sizeof buf - 1) < 0)
        rb_sys_fail("gethostname");

    buf[sizeof buf - 1] = '\0';
    return rb_str_new2(buf);
}
#else
#ifdef HAVE_UNAME

#include <sys/utsname.h>

static VALUE
sock_gethostname(VALUE obj)
{
    struct utsname un;

    rb_secure(3);
    uname(&un);
    return rb_str_new2(un.nodename);
}
#else
static VALUE
sock_gethostname(VALUE obj)
{
    rb_notimplement();
}
#endif
#endif

static VALUE
make_addrinfo(struct addrinfo *res0)
{
    VALUE base, ary;
    struct addrinfo *res;

    if (res0 == NULL) {
        rb_raise(rb_eSocket, "host not found");
    }
    base = rb_ary_new();
    for (res = res0; res; res = res->ai_next) {
        ary = ipaddr(res->ai_addr, do_not_reverse_lookup);
        if (res->ai_canonname) {
            RARRAY_PTR(ary)[2] = rb_str_new2(res->ai_canonname);
        }
        rb_ary_push(ary, INT2FIX(res->ai_family));
        rb_ary_push(ary, INT2FIX(res->ai_socktype));
        rb_ary_push(ary, INT2FIX(res->ai_protocol));
        rb_ary_push(base, ary);
    }
    return base;
}

static VALUE
sock_sockaddr(struct sockaddr *addr, size_t len)
{
    char *ptr;

    switch (addr->sa_family) {
      case AF_INET:
        ptr = (char*)&((struct sockaddr_in*)addr)->sin_addr.s_addr;
        len = sizeof(((struct sockaddr_in*)addr)->sin_addr.s_addr);
        break;
#ifdef INET6
      case AF_INET6:
        ptr = (char*)&((struct sockaddr_in6*)addr)->sin6_addr.s6_addr;
        len = sizeof(((struct sockaddr_in6*)addr)->sin6_addr.s6_addr);
        break;
#endif
      default:
        rb_raise(rb_eSocket, "unknown socket family:%d", addr->sa_family);
        break;
    }
    return rb_str_new(ptr, len);
}

static VALUE
sock_s_gethostbyname(VALUE obj, VALUE host)
{
    rb_secure(3);
    return make_hostent(host, sock_addrinfo(host, Qnil, SOCK_STREAM, AI_CANONNAME), sock_sockaddr);
}

static VALUE
sock_s_gethostbyaddr(int argc, VALUE *argv)
{
    VALUE addr, type;
    struct hostent *h;
    struct sockaddr *sa;
    char **pch;
    VALUE ary, names;
    int t = AF_INET;

    rb_scan_args(argc, argv, "11", &addr, &type);
    sa = (struct sockaddr*)StringValuePtr(addr);
    if (!NIL_P(type)) {
        t = NUM2INT(type);
    }
#ifdef INET6
    else if (RSTRING_LEN(addr) == 16) {
        t = AF_INET6;
    }
#endif
    h = gethostbyaddr(RSTRING_PTR(addr), RSTRING_LEN(addr), t);
    if (h == NULL) {
#ifdef HAVE_HSTRERROR
        extern int h_errno;
        rb_raise(rb_eSocket, "%s", (char*)hstrerror(h_errno));
#else
        rb_raise(rb_eSocket, "host not found");
#endif
    }
    ary = rb_ary_new();
    rb_ary_push(ary, rb_str_new2(h->h_name));
    names = rb_ary_new();
    rb_ary_push(ary, names);
    if (h->h_aliases != NULL) {
        for (pch = h->h_aliases; *pch; pch++) {
            rb_ary_push(names, rb_str_new2(*pch));
        }
    }
    rb_ary_push(ary, INT2NUM(h->h_addrtype));
#ifdef h_addr
    for (pch = h->h_addr_list; *pch; pch++) {
        rb_ary_push(ary, rb_str_new(*pch, h->h_length));
    }
#else
    rb_ary_push(ary, rb_str_new(h->h_addr, h->h_length));
#endif

    return ary;
}

static VALUE
sock_s_getservbyname(int argc, VALUE *argv)
{
    VALUE service, proto;
    struct servent *sp;
    int port;
    const char *servicename, *protoname = "tcp";

    rb_scan_args(argc, argv, "11", &service, &proto);
    StringValue(service);
    if (!NIL_P(proto)) StringValue(proto);
    servicename = StringValueCStr(service);
    if (!NIL_P(proto)) protoname = StringValueCStr(proto);
    sp = getservbyname(servicename, protoname);
    if (sp) {
        port = ntohs(sp->s_port);
    }
    else {
        char *end;

        port = STRTOUL(servicename, &end, 0);
        if (*end != '\0') {
            rb_raise(rb_eSocket, "no such service %s/%s", servicename, protoname);
        }
    }
    return INT2FIX(port);
}

static VALUE
sock_s_getservbyport(int argc, VALUE *argv)
{
    VALUE port, proto;
    struct servent *sp;
    long portnum;
    const char *protoname = "tcp";

    rb_scan_args(argc, argv, "11", &port, &proto);
    portnum = NUM2LONG(port);
    if (portnum != (uint16_t)portnum) {
        const char *s = portnum > 0 ? "big" : "small";
        rb_raise(rb_eRangeError, "integer %ld too %s to convert into `int16_t'", portnum, s);
    }
    if (!NIL_P(proto)) protoname = StringValueCStr(proto);

    sp = getservbyport((int)htons((uint16_t)portnum), protoname);
    if (!sp) {
        rb_raise(rb_eSocket, "no such service for port %d/%s", (int)portnum, protoname);
    }
    return rb_tainted_str_new2(sp->s_name);
}

static VALUE
sock_s_getaddrinfo(int argc, VALUE *argv)
{
    VALUE host, port, family, socktype, protocol, flags, ret;
    char *ap;
    struct addrinfo hints, *res;

    rb_scan_args(argc, argv, "24", &host, &port, &family, &socktype, &protocol, &flags);

    MEMZERO(&hints, struct addrinfo, 1);
    if (NIL_P(family)) {
        hints.ai_family = PF_UNSPEC;
    }
    else if (FIXNUM_P(family)) {
        hints.ai_family = FIX2INT(family);
    }
    else if ((ap = StringValuePtr(family)) != 0) {
        if (strcmp(ap, "AF_INET") == 0) {
            hints.ai_family = PF_INET;
        }
#ifdef INET6
        else if (strcmp(ap, "AF_INET6") == 0) {
            hints.ai_family = PF_INET6;
        }
#endif
    }

    if (!NIL_P(socktype)) {
        hints.ai_socktype = NUM2INT(socktype);
    }
    if (!NIL_P(protocol)) {
        hints.ai_protocol = NUM2INT(protocol);
    }
    if (!NIL_P(flags)) {
        hints.ai_flags = NUM2INT(flags);
    }
    res = sock_getaddrinfo(host, port, &hints, 0);

    ret = make_addrinfo(res);
    freeaddrinfo(res);
    return ret;
}

static VALUE
sock_s_getnameinfo(int argc, VALUE *argv)
{
    VALUE sa, af = Qnil, host = Qnil, port = Qnil, flags, tmp;
    char *hptr, *pptr;
    char hbuf[1024], pbuf[1024];
    int fl;
    struct addrinfo hints, *res = NULL, *r;
    int error;
    struct sockaddr_storage ss;
    struct sockaddr *sap;
    char *ap;

    sa = flags = Qnil;
    rb_scan_args(argc, argv, "11", &sa, &flags);

    fl = 0;
    if (!NIL_P(flags)) {
        fl = NUM2INT(flags);
    }
    tmp = rb_check_string_type(sa);
    if (!NIL_P(tmp)) {
        sa = tmp;
        if (sizeof(ss) < RSTRING_LEN(sa)) {
            rb_raise(rb_eTypeError, "sockaddr length too big");
        }
        memcpy(&ss, RSTRING_PTR(sa), RSTRING_LEN(sa));
        if (RSTRING_LEN(sa) != SA_LEN((struct sockaddr*)&ss)) {
            rb_raise(rb_eTypeError, "sockaddr size differs - should not happen");
        }
        sap = (struct sockaddr*)&ss;
        goto call_nameinfo;
    }
    tmp = rb_check_array_type(sa);
    if (!NIL_P(tmp)) {
        sa = tmp;
        MEMZERO(&hints, struct addrinfo, 1);
        if (RARRAY_LEN(sa) == 3) {
            af = RARRAY_PTR(sa)[0];
            port = RARRAY_PTR(sa)[1];
            host = RARRAY_PTR(sa)[2];
        }
        else if (RARRAY_LEN(sa) >= 4) {
            af = RARRAY_PTR(sa)[0];
            port = RARRAY_PTR(sa)[1];
            host = RARRAY_PTR(sa)[3];
            if (NIL_P(host)) {
                host = RARRAY_PTR(sa)[2];
            }
            else {
                /*
                 * 4th element holds numeric form, don't resolve.
                 * see ipaddr().
                 */
#ifdef AI_NUMERICHOST /* AIX 4.3.3 doesn't have AI_NUMERICHOST. */
                hints.ai_flags |= AI_NUMERICHOST;
#endif
            }
        }
        else {
            rb_raise(rb_eArgError, "array size should be 3 or 4, %ld given",
                     RARRAY_LEN(sa));
        }
        /* host */
        if (NIL_P(host)) {
            hptr = NULL;
        }
        else {
            strncpy(hbuf, StringValuePtr(host), sizeof(hbuf));
            hbuf[sizeof(hbuf) - 1] = '\0';
            hptr = hbuf;
        }
        /* port */
        if (NIL_P(port)) {
            strcpy(pbuf, "0");
            pptr = NULL;
        }
        else if (FIXNUM_P(port)) {
            snprintf(pbuf, sizeof(pbuf), "%ld", NUM2LONG(port));
            pptr = pbuf;
        }
        else {
            strncpy(pbuf, StringValuePtr(port), sizeof(pbuf));
            pbuf[sizeof(pbuf) - 1] = '\0';
            pptr = pbuf;
        }
        hints.ai_socktype = (fl & NI_DGRAM) ? SOCK_DGRAM : SOCK_STREAM;
        /* af */
        if (NIL_P(af)) {
            hints.ai_family = PF_UNSPEC;
        }
        else if (FIXNUM_P(af)) {
            hints.ai_family = FIX2INT(af);
        }
        else if ((ap = StringValuePtr(af)) != 0) {
            if (strcmp(ap, "AF_INET") == 0) {
                hints.ai_family = PF_INET;
            }
#ifdef INET6
            else if (strcmp(ap, "AF_INET6") == 0) {
                hints.ai_family = PF_INET6;
            }
#endif
        }
        error = getaddrinfo(hptr, pptr, &hints, &res);
        if (error) goto error_exit_addr;
        sap = res->ai_addr;
    }
    else {
        rb_raise(rb_eTypeError, "expecting String or Array");
    }

  call_nameinfo:
    error = getnameinfo(sap, SA_LEN(sap), hbuf, sizeof(hbuf),
                        pbuf, sizeof(pbuf), fl);
    if (error) goto error_exit_name;
    if (res) {
        for (r = res->ai_next; r; r = r->ai_next) {
            char hbuf2[1024], pbuf2[1024];

            sap = r->ai_addr;
            error = getnameinfo(sap, SA_LEN(sap), hbuf2, sizeof(hbuf2),
                                pbuf2, sizeof(pbuf2), fl);
            if (error) goto error_exit_name;
            if (strcmp(hbuf, hbuf2) != 0|| strcmp(pbuf, pbuf2) != 0) {
                freeaddrinfo(res);
                rb_raise(rb_eSocket, "sockaddr resolved to multiple nodename");
            }
        }
        freeaddrinfo(res);
    }
    return rb_assoc_new(rb_str_new2(hbuf), rb_str_new2(pbuf));

  error_exit_addr:
    if (res) freeaddrinfo(res);
    raise_socket_error("getaddrinfo", error);

  error_exit_name:
    if (res) freeaddrinfo(res);
    raise_socket_error("getnameinfo", error);
}

static VALUE
sock_s_pack_sockaddr_in(VALUE self, VALUE port, VALUE host)
{
    struct addrinfo *res = sock_addrinfo(host, port, 0, 0);
    VALUE addr = rb_str_new((char*)res->ai_addr, res->ai_addrlen);

    freeaddrinfo(res);
    OBJ_INFECT(addr, port);
    OBJ_INFECT(addr, host);

    return addr;
}

static VALUE
sock_s_unpack_sockaddr_in(VALUE self, VALUE addr)
{
    struct sockaddr_in * sockaddr;
    VALUE host;

    sockaddr = (struct sockaddr_in*)StringValuePtr(addr);
    if (RSTRING_LEN(addr) <
        (char*)&((struct sockaddr *)sockaddr)->sa_family +
        sizeof(((struct sockaddr *)sockaddr)->sa_family) -
        (char*)sockaddr)
        rb_raise(rb_eArgError, "too short sockaddr");
    if (((struct sockaddr *)sockaddr)->sa_family != AF_INET
#ifdef INET6
        && ((struct sockaddr *)sockaddr)->sa_family != AF_INET6
#endif
        ) {
#ifdef INET6
        rb_raise(rb_eArgError, "not an AF_INET/AF_INET6 sockaddr");
#else
        rb_raise(rb_eArgError, "not an AF_INET sockaddr");
#endif
    }
    host = make_ipaddr((struct sockaddr*)sockaddr);
    OBJ_INFECT(host, addr);
    return rb_assoc_new(INT2NUM(ntohs(sockaddr->sin_port)), host);
}

#ifdef HAVE_SYS_UN_H
static VALUE
sock_s_pack_sockaddr_un(VALUE self, VALUE path)
{
    struct sockaddr_un sockaddr;
    char *sun_path;
    VALUE addr;

    MEMZERO(&sockaddr, struct sockaddr_un, 1);
    sockaddr.sun_family = AF_UNIX;
    sun_path = StringValueCStr(path);
    if (sizeof(sockaddr.sun_path) <= strlen(sun_path)) {
        rb_raise(rb_eArgError, "too long unix socket path (max: %dbytes)",
            (int)sizeof(sockaddr.sun_path)-1);
    }
    strncpy(sockaddr.sun_path, sun_path, sizeof(sockaddr.sun_path)-1);
    addr = rb_str_new((char*)&sockaddr, sizeof(sockaddr));
    OBJ_INFECT(addr, path);

    return addr;
}

static VALUE
sock_s_unpack_sockaddr_un(VALUE self, VALUE addr)
{
    struct sockaddr_un * sockaddr;
    const char *sun_path;
    VALUE path;

    sockaddr = (struct sockaddr_un*)StringValuePtr(addr);
    if (RSTRING_LEN(addr) <
        (char*)&((struct sockaddr *)sockaddr)->sa_family +
        sizeof(((struct sockaddr *)sockaddr)->sa_family) -
        (char*)sockaddr)
        rb_raise(rb_eArgError, "too short sockaddr");
    if (((struct sockaddr *)sockaddr)->sa_family != AF_UNIX) {
        rb_raise(rb_eArgError, "not an AF_UNIX sockaddr");
    }
    if (sizeof(struct sockaddr_un) < RSTRING_LEN(addr)) {
        rb_raise(rb_eTypeError, "too long sockaddr_un - %ld longer than %d",
                 RSTRING_LEN(addr), (int)sizeof(struct sockaddr_un));
    }
    sun_path = unixpath(sockaddr, RSTRING_LEN(addr));
    if (sizeof(struct sockaddr_un) == RSTRING_LEN(addr) &&
        sun_path == sockaddr->sun_path &&
        sun_path + strlen(sun_path) == RSTRING_PTR(addr) + RSTRING_LEN(addr)) {
        rb_raise(rb_eArgError, "sockaddr_un.sun_path not NUL terminated");
    }
    path = rb_str_new2(sun_path);
    OBJ_INFECT(path, addr);
    return path;
}
#endif

static void
sock_define_const(const char *name, int value, VALUE mConst)
{
    rb_define_const(rb_cSocket, name, INT2FIX(value));
    rb_define_const(mConst, name, INT2FIX(value));
}

static void
sock_define_uconst(const char *name, unsigned int value, VALUE mConst)
{
    rb_define_const(rb_cSocket, name, UINT2NUM(value));
    rb_define_const(mConst, name, UINT2NUM(value));
}

#define sock_define_const(name, value) sock_define_const(name, value, mConst)
#define sock_define_uconst(name, value) sock_define_uconst(name, value, mConst)

/*
 * Class +Socket+ provides access to the underlying operating system
 * socket implementations. It can be used to provide more operating system
 * specific functionality than the protocol-specific socket classes but at the
 * expense of greater complexity. In particular, the class handles addresses
 * using +struct+ sockaddr structures packed into Ruby strings, which can be
 * a joy to manipulate.
 * 
 * === Exception Handling
 * Ruby's implementation of +Socket+ causes an exception to be raised
 * based on the error generated by the system dependent implementation.
 * This is why the methods are documented in a way that isolate
 * Unix-based system exceptions from Windows based exceptions. If more
 * information on particular exception is needed please refer to the 
 * Unix manual pages or the Windows WinSock reference.
 * 
 * 
 * === Documentation by
 * * Zach Dennis
 * * Sam Roberts
 * * <em>Programming Ruby</em> from The Pragmatic Bookshelf.  
 * 
 * Much material in this documentation is taken with permission from  
 * <em>Programming Ruby</em> from The Pragmatic Bookshelf.  
 */
void
Init_socket()
{
    VALUE mConst;

    rb_eSocket = rb_define_class("SocketError", rb_eStandardError);

    rb_cBasicSocket = rb_define_class("BasicSocket", rb_cIO);
    rb_undef_method(rb_cBasicSocket, "initialize");

    rb_define_singleton_method(rb_cBasicSocket, "do_not_reverse_lookup",
                               bsock_do_not_rev_lookup, 0);
    rb_define_singleton_method(rb_cBasicSocket, "do_not_reverse_lookup=",
                               bsock_do_not_rev_lookup_set, 1);
    rb_define_singleton_method(rb_cBasicSocket, "for_fd", bsock_s_for_fd, 1);

    rb_define_method(rb_cBasicSocket, "close_read", bsock_close_read, 0);
    rb_define_method(rb_cBasicSocket, "close_write", bsock_close_write, 0);
    rb_define_method(rb_cBasicSocket, "shutdown", bsock_shutdown, -1);
    rb_define_method(rb_cBasicSocket, "setsockopt", bsock_setsockopt, 3);
    rb_define_method(rb_cBasicSocket, "getsockopt", bsock_getsockopt, 2);
    rb_define_method(rb_cBasicSocket, "getsockname", bsock_getsockname, 0);
    rb_define_method(rb_cBasicSocket, "getpeername", bsock_getpeername, 0);
    rb_define_method(rb_cBasicSocket, "send", bsock_send, -1);
    rb_define_method(rb_cBasicSocket, "recv", bsock_recv, -1);
    rb_define_method(rb_cBasicSocket, "recv_nonblock", bsock_recv_nonblock, -1);
    rb_define_method(rb_cBasicSocket, "do_not_reverse_lookup", bsock_do_not_reverse_lookup, 0);
    rb_define_method(rb_cBasicSocket, "do_not_reverse_lookup=", bsock_do_not_reverse_lookup_set, 1);

    rb_cIPSocket = rb_define_class("IPSocket", rb_cBasicSocket);
    rb_define_method(rb_cIPSocket, "addr", ip_addr, 0);
    rb_define_method(rb_cIPSocket, "peeraddr", ip_peeraddr, 0);
    rb_define_method(rb_cIPSocket, "recvfrom", ip_recvfrom, -1);
    rb_define_singleton_method(rb_cIPSocket, "getaddress", ip_s_getaddress, 1);

    rb_cTCPSocket = rb_define_class("TCPSocket", rb_cIPSocket);
    rb_define_singleton_method(rb_cTCPSocket, "gethostbyname", tcp_s_gethostbyname, 1);
    rb_define_method(rb_cTCPSocket, "initialize", tcp_init, -1);

#ifdef SOCKS
    rb_cSOCKSSocket = rb_define_class("SOCKSSocket", rb_cTCPSocket);
    rb_define_method(rb_cSOCKSSocket, "initialize", socks_init, 2);
#ifdef SOCKS5
    rb_define_method(rb_cSOCKSSocket, "close", socks_s_close, 0);
#endif
#endif

    rb_cTCPServer = rb_define_class("TCPServer", rb_cTCPSocket);
    rb_define_method(rb_cTCPServer, "accept", tcp_accept, 0);
    rb_define_method(rb_cTCPServer, "accept_nonblock", tcp_accept_nonblock, 0);
    rb_define_method(rb_cTCPServer, "sysaccept", tcp_sysaccept, 0);
    rb_define_method(rb_cTCPServer, "initialize", tcp_svr_init, -1);
    rb_define_method(rb_cTCPServer, "listen", sock_listen, 1);

    rb_cUDPSocket = rb_define_class("UDPSocket", rb_cIPSocket);
    rb_define_method(rb_cUDPSocket, "initialize", udp_init, -1);
    rb_define_method(rb_cUDPSocket, "connect", udp_connect, 2);
    rb_define_method(rb_cUDPSocket, "bind", udp_bind, 2);
    rb_define_method(rb_cUDPSocket, "send", udp_send, -1);
    rb_define_method(rb_cUDPSocket, "recvfrom_nonblock", udp_recvfrom_nonblock, -1);

#ifdef HAVE_SYS_UN_H
    rb_cUNIXSocket = rb_define_class("UNIXSocket", rb_cBasicSocket);
    rb_define_method(rb_cUNIXSocket, "initialize", unix_init, 1);
    rb_define_method(rb_cUNIXSocket, "path", unix_path, 0);
    rb_define_method(rb_cUNIXSocket, "addr", unix_addr, 0);
    rb_define_method(rb_cUNIXSocket, "peeraddr", unix_peeraddr, 0);
    rb_define_method(rb_cUNIXSocket, "recvfrom", unix_recvfrom, -1);
    rb_define_method(rb_cUNIXSocket, "send_io", unix_send_io, 1);
    rb_define_method(rb_cUNIXSocket, "recv_io", unix_recv_io, -1);
    rb_define_singleton_method(rb_cUNIXSocket, "socketpair", unix_s_socketpair, -1);
    rb_define_singleton_method(rb_cUNIXSocket, "pair", unix_s_socketpair, -1);

    rb_cUNIXServer = rb_define_class("UNIXServer", rb_cUNIXSocket);
    rb_define_method(rb_cUNIXServer, "initialize", unix_svr_init, 1);
    rb_define_method(rb_cUNIXServer, "accept", unix_accept, 0);
    rb_define_method(rb_cUNIXServer, "accept_nonblock", unix_accept_nonblock, 0);
    rb_define_method(rb_cUNIXServer, "sysaccept", unix_sysaccept, 0);
    rb_define_method(rb_cUNIXServer, "listen", sock_listen, 1);
#endif

    rb_cSocket = rb_define_class("Socket", rb_cBasicSocket);

    rb_define_method(rb_cSocket, "initialize", sock_initialize, 3);
    rb_define_method(rb_cSocket, "connect", sock_connect, 1);
    rb_define_method(rb_cSocket, "connect_nonblock", sock_connect_nonblock, 1);
    rb_define_method(rb_cSocket, "bind", sock_bind, 1);
    rb_define_method(rb_cSocket, "listen", sock_listen, 1);
    rb_define_method(rb_cSocket, "accept", sock_accept, 0);
    rb_define_method(rb_cSocket, "accept_nonblock", sock_accept_nonblock, 0);
    rb_define_method(rb_cSocket, "sysaccept", sock_sysaccept, 0);

    rb_define_method(rb_cSocket, "recvfrom", sock_recvfrom, -1);
    rb_define_method(rb_cSocket, "recvfrom_nonblock", sock_recvfrom_nonblock, -1);

    rb_define_singleton_method(rb_cSocket, "socketpair", sock_s_socketpair, 3);
    rb_define_singleton_method(rb_cSocket, "pair", sock_s_socketpair, 3);
    rb_define_singleton_method(rb_cSocket, "gethostname", sock_gethostname, 0);
    rb_define_singleton_method(rb_cSocket, "gethostbyname", sock_s_gethostbyname, 1);
    rb_define_singleton_method(rb_cSocket, "gethostbyaddr", sock_s_gethostbyaddr, -1);
    rb_define_singleton_method(rb_cSocket, "getservbyname", sock_s_getservbyname, -1);
    rb_define_singleton_method(rb_cSocket, "getservbyport", sock_s_getservbyport, -1);
    rb_define_singleton_method(rb_cSocket, "getaddrinfo", sock_s_getaddrinfo, -1);
    rb_define_singleton_method(rb_cSocket, "getnameinfo", sock_s_getnameinfo, -1);
    rb_define_singleton_method(rb_cSocket, "sockaddr_in", sock_s_pack_sockaddr_in, 2);
    rb_define_singleton_method(rb_cSocket, "pack_sockaddr_in", sock_s_pack_sockaddr_in, 2);
    rb_define_singleton_method(rb_cSocket, "unpack_sockaddr_in", sock_s_unpack_sockaddr_in, 1);
#ifdef HAVE_SYS_UN_H
    rb_define_singleton_method(rb_cSocket, "sockaddr_un", sock_s_pack_sockaddr_un, 1);
    rb_define_singleton_method(rb_cSocket, "pack_sockaddr_un", sock_s_pack_sockaddr_un, 1);
    rb_define_singleton_method(rb_cSocket, "unpack_sockaddr_un", sock_s_unpack_sockaddr_un, 1);
#endif

    /* constants */
    mConst = rb_define_module_under(rb_cSocket, "Constants");
#include "constants.h"
#ifdef INET6 /* IPv6 is not supported although AF_INET6 is defined on bcc32/mingw */
    sock_define_const("AF_INET6", AF_INET6);
    sock_define_const("PF_INET6", PF_INET6);
#endif
}
/* */