An attempt to establish a TCP/IP connection to a host (C socket)

conn.c

/* written by ooharak 2012. */
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <poll.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define HOST_IP "8.8.8.8"
#define HOST_PORT 80
#define TIMEOUT_MILLIS 1234

#define maybe(s) (errno=0,_maybe(#s, s))

int _maybe(char *s, int r);
int
_maybe(char *s, int r)
{
  if (r == -1) {
    perror(s);
    exit(1);
  }
  return r;
}


int
main(int argc, char *argv[])
{
  int timeout = TIMEOUT_MILLIS;
  int fd;
  int flag;
  struct sockaddr_in addr = { AF_INET, htons(HOST_PORT), inet_addr(HOST_IP) };
  int pollresult = -1;
  
  struct pollfd aPollfd;
  aPollfd.events = POLLOUT;
  
  fd = maybe(socket(PF_INET, SOCK_STREAM, 0));
  flag = maybe(fcntl(fd, F_GETFL));
  maybe(fcntl(fd, F_SETFL, flag|O_NONBLOCK));
  
  if (-1 == connect(fd, (struct sockaddr *) &addr, sizeof(addr))) {
    if (EINPROGRESS == errno) {
      //ok
    } else {
      perror("connect");
      exit(4);
    }
  } else {
    puts("connection succeeded before polling");
  }
  
  aPollfd.fd = fd;
  pollresult = maybe(poll(&aPollfd, 1, timeout));
  if (0 == pollresult) {
    puts("timeout");
  } else {
    puts("success");
  }
  
  flag = maybe(fcntl(fd, F_GETFL));
  maybe(fcntl(fd, F_SETFL, flag|O_NONBLOCK));
  maybe(shutdown(fd, SHUT_RDWR));
  maybe(close(fd));
  
  exit(0);
}