1 #include <netinet/ip.h> 2 #include <stdio.h> 3 #include <stdlib.h> 4 #include <string.h> 5 #include <sys/types.h> 6 #include <sys/socket.h> 7 8 #define PORT 12345 9 10 int 11 main (int argc, char **argv) 12 { 13 int fd; 14 struct sockaddr_in sa; 15 struct msghdr msg; 16 struct iovec iov[2]; 17 18 fd = socket (AF_INET, SOCK_DGRAM, 0); 19 if (fd == -1) 20 { 21 perror ("socket()"); 22 exit (EXIT_FAILURE); 23 } 24 25 sa.sin_family = AF_INET; 26 sa.sin_addr.s_addr = htonl (INADDR_LOOPBACK); 27 sa.sin_port = htons (PORT); 28 if (connect (fd, (struct sockaddr *) &sa, sizeof (sa)) == -1) 29 { 30 perror ("connect ()"); 31 exit (EXIT_FAILURE); 32 } 33 34 // Create msg_hdr. Oops, we forget to set msg_name... 35 msg.msg_namelen = 0; 36 iov[0].iov_base = "one"; 37 iov[0].iov_len = 3; 38 iov[1].iov_base = "two"; 39 iov[1].iov_len = 3; 40 msg.msg_iov = &iov[0]; 41 msg.msg_iovlen = 2; 42 msg.msg_control = NULL; 43 msg.msg_controllen = 0; 44 45 size_t s = sendmsg (fd, &msg, 0); 46 47 // Note how we now do set msg_name, but don't set msg_flags. 48 // The msg_flags field is ignored by sendmsg. 49 msg.msg_name = NULL; 50 51 fd = socket (AF_INET, SOCK_DGRAM, 0); 52 if (fd == -1) 53 { 54 perror ("socket()"); 55 exit (EXIT_FAILURE); 56 } 57 58 if (connect (fd, (struct sockaddr *) &sa, sizeof (sa)) == -1) 59 { 60 perror ("connect ()"); 61 exit (EXIT_FAILURE); 62 } 63 64 s = sendmsg (fd, &msg, 0); 65 if (s == -1) 66 { 67 perror ("sendmsg ()"); 68 exit (EXIT_FAILURE); 69 } 70 else 71 fprintf (stderr, "sendmsg: %d\n", (int) s); 72 73 return 0; 74 } 75
