1 #include <stdio.h> 2 #include <stdlib.h> 3 #include <string.h> 4 #include <sys/types.h> 5 #include <sys/socket.h> 6 #include <netinet/in.h> 7 #include <netinet/ip.h> 8 9 #define PORT 12345 10 11 int 12 main (int argc, char **argv) 13 { 14 int fd; 15 struct sockaddr_in sa; 16 struct msghdr msg; 17 struct iovec iov[2]; 18 19 fd = socket (AF_INET, SOCK_DGRAM, 0); 20 if (fd == -1) 21 { 22 perror ("socket()"); 23 exit (EXIT_FAILURE); 24 } 25 26 sa.sin_family = AF_INET; 27 sa.sin_addr.s_addr = htonl (INADDR_LOOPBACK); 28 sa.sin_port = htons (PORT); 29 if (connect (fd, (struct sockaddr *) &sa, sizeof (sa)) == -1) 30 { 31 perror ("connect ()"); 32 exit (EXIT_FAILURE); 33 } 34 35 // Create msg_hdr. Oops, we forget to set msg_name... 36 msg.msg_namelen = 0; 37 iov[0].iov_base = "one"; 38 iov[0].iov_len = 3; 39 iov[1].iov_base = "two"; 40 iov[1].iov_len = 3; 41 msg.msg_iov = &iov[0]; 42 msg.msg_iovlen = 2; 43 msg.msg_control = NULL; 44 msg.msg_controllen = 0; 45 46 size_t s = sendmsg (fd, &msg, 0); 47 48 // Note how we now do set msg_name, but don't set msg_flags. 49 // The msg_flags field is ignored by sendmsg. 50 msg.msg_name = NULL; 51 52 fd = socket (AF_INET, SOCK_DGRAM, 0); 53 if (fd == -1) 54 { 55 perror ("socket()"); 56 exit (EXIT_FAILURE); 57 } 58 59 if (connect (fd, (struct sockaddr *) &sa, sizeof (sa)) == -1) 60 { 61 perror ("connect ()"); 62 exit (EXIT_FAILURE); 63 } 64 65 s = sendmsg (fd, &msg, 0); 66 if (s == -1) 67 { 68 perror ("sendmsg ()"); 69 exit (EXIT_FAILURE); 70 } 71 else 72 fprintf (stderr, "sendmsg: %d\n", (int) s); 73 74 return 0; 75 } 76
