Create an AF_INET socket and connect() it to itself

tcp-self-connect.c

/*
 * Copyright (c) 2012, Ben Noordhuis <info@bnoordhuis.nl>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>

#define E(expr) \
  do { \
    errno = 0; \
    do { expr; } while (0); \
    if (errno) perror(#expr), abort(); \
  } \
  while (0)

int main(void)
{
  struct sockaddr_in sin;
  char buf[32];
  int on;
  int fd;

  memset(&sin, 0, sizeof(sin));
  sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
  sin.sin_family = AF_INET;
  sin.sin_port = htons(1337);
  on = 1;

  E(fd = socket(AF_INET, SOCK_STREAM, 0));
  E(setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)));
  E(bind(fd, (struct sockaddr *) &sin, sizeof(sin)));
//  E(listen(fd, 32)); // should make connect() fail with EISCONN
  E(connect(fd, (struct sockaddr *) &sin, sizeof(sin)));
//  E(listen(fd, 32)); // should fail with EOPNOTSUPP

  E(write(fd, "test", 4));
  E(read(fd, buf, sizeof(buf))); // reads "test"

  return 0;
}