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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#define PORT 12345
int
main (int argc, char **argv)
{
int fd;
struct sockaddr_in sa;
struct msghdr msg;
struct iovec iov[2];
fd = socket (AF_INET, SOCK_DGRAM, 0);
if (fd == -1)
{
perror ("socket()");
exit (EXIT_FAILURE);
}
sa.sin_family = AF_INET;
sa.sin_addr.s_addr = htonl (INADDR_LOOPBACK);
sa.sin_port = htons (PORT);
if (connect (fd, (struct sockaddr *) &sa, sizeof (sa)) == -1)
{
perror ("connect ()");
exit (EXIT_FAILURE);
}
// Create msg_hdr. Oops, we forget to set msg_name...
msg.msg_namelen = 0;
iov[0].iov_base = "one";
iov[0].iov_len = 3;
iov[1].iov_base = "two";
iov[1].iov_len = 3;
msg.msg_iov = &iov[0];
msg.msg_iovlen = 2;
msg.msg_control = NULL;
msg.msg_controllen = 0;
size_t s = sendmsg (fd, &msg, 0);
// Note how we now do set msg_name, but don't set msg_flags.
// The msg_flags field is ignored by sendmsg.
msg.msg_name = NULL;
fd = socket (AF_INET, SOCK_DGRAM, 0);
if (fd == -1)
{
perror ("socket()");
exit (EXIT_FAILURE);
}
if (connect (fd, (struct sockaddr *) &sa, sizeof (sa)) == -1)
{
perror ("connect ()");
exit (EXIT_FAILURE);
}
s = sendmsg (fd, &msg, 0);
if (s == -1)
{
perror ("sendmsg ()");
exit (EXIT_FAILURE);
}
else
fprintf (stderr, "sendmsg: %d\n", (int) s);
return 0;
}
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