udpclient.c

Linux平台上UDP通信的client端代码。

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <arpa/inet.h>
#include <string.h>
#include <errno.h>

#define BUFFER_SIZE	1024

int
main (int argc, char **argv)
{
  int fd;

  int rand = 0;


  // XXX: step 1, socket();

  int socket (int domain, int type, int protocol);

  if ((fd = socket (PF_INET, SOCK_DGRAM, 0)) < 0)
    {
      fprintf (stderr, "Create a new UDP socket failed: %s\n",
	       strerror (errno));
      exit (1);
    }

  fd_set rset;
  fd_set wset;
  fd_set eset;
  FD_ZERO (&rset);
  FD_ZERO (&wset);
  FD_ZERO (&eset);
  FD_SET (fd, &eset);
  FD_SET (fd, &rset);
  FD_SET (fd, &wset);


  char line[BUFFER_SIZE] = "hello";
  struct sockaddr_in remote_address;
  ssize_t sent;
  memset (&remote_address, 0, sizeof (remote_address));
  remote_address.sin_family = PF_INET;
  remote_address.sin_port = htons (atoi (argv[2]));
  remote_address.sin_addr.s_addr = inet_addr (argv[1]);

  struct sockaddr_in peer_address;
  socklen_t peer_address_length;
  ssize_t recv;
  peer_address_length = sizeof (peer_address);


  struct timeval tv;
  tv.tv_sec = 1;
  tv.tv_usec = 0;

  while (1)
    {
     rand = random () % 3;
#if _DEBUG_
      printf ("%d\n", rand);
#endif
      sleep (rand);
    //sleep(1);
      int sel;
      if ((sel = select (fd + 1, &rset, &wset, &eset, &tv)) < 0)
	{
	  if (EINTR == errno)
	    {
	      continue;
	    }
	  else
	    {
	      fprintf (stderr, "select failed:%s\n", strerror (errno));
	    }
	}
      else if (0 == sel)
	{
	  fprintf (stdout, "time out...\n");
	}
      else
	{
	  if (FD_ISSET (fd, &wset))
	    {
	    resend:
	      if ((sent =
		   sendto (fd, line, strlen (line), 0,
			   (struct sockaddr *) &remote_address,
			   sizeof (remote_address))) < 0)
		{
		  if (errno == EINTR)
		    {
		      goto resend;
		    }
		  else
		    {
		      fprintf (stderr, "sendto() failed: %s\n",
			       strerror (errno));
		    }
		}
	      else
		{
		  fprintf (stdout, "Sent %d bytes to remote host.\n", sent);
		}
	    }
	}

      FD_SET(fd,&rset);
      if ((sel = select (fd + 1, &rset, &wset, &eset, &tv)) < 0)
	{
	  if (EINTR == errno)
	    {
	      continue;
	    }
	  else
	    {
	      fprintf (stderr, "select failed:%s\n", strerror (errno));
	    }
	}
      else if (0 == sel)
	{
	  fprintf (stdout, "time out...\n");
	}
      else
	{

	  if (FD_ISSET (fd, &rset))
	    {
#if _DEBUG_
	      printf ("enter read\n");
#endif
	    re_receive:
	      if ((recv =
		   recvfrom (fd, line, BUFFER_SIZE, 0,
			     (struct sockaddr *) &peer_address,
			     &peer_address_length)) < 0)
		{
		  if (errno == EINTR)
		    {
		      goto re_receive;
		    }
		  else
		    {
		      fprintf (stderr, "recvfrom() failed: %s\n",
			       strerror (errno));
		    }
		}
	      else
		{
		  fprintf (stdout, "INFO: read %d bytes from %s:%d\n", recv,
			   inet_ntoa (peer_address.sin_addr),
			   ntohs (peer_address.sin_port));
		  fprintf (stdout, "DEBUG: %s\n", line);
		}
	    }
	}
    }

  close (fd);
  return 0;
}