1 .\" Copyright (c) 1986 Regents of the University of California. 2 .\" All rights reserved. The Berkeley software License Agreement 3 .\" specifies the terms and conditions for redistribution. 4 .\" 5 .\" @(#)dgramsend.c 6.2 (Berkeley) 05/08/86 6 .\" 7 #include <sys/types.h> 8 #include <sys/socket.h> 9 #include <netinet/in.h> 10 #include <netdb.h> 11 #include <stdio.h> 12 13 #define DATA "The sea is calm tonight, the tide is full . . ." 14 15 /* 16 * Here I send a datagram to a receiver whose name I get from the command 17 * line arguments. The form of the command line is dgramsend hostname 18 * portnumber 19 */ 20 21 main(argc, argv) 22 int argc; 23 char *argv[]; 24 { 25 int sock; 26 struct sockaddr_in name; 27 struct hostent *hp, *gethostbyname(); 28 29 /* Create socket on which to send. */ 30 sock = socket(AF_INET, SOCK_DGRAM, 0); 31 if (sock < 0) { 32 perror("opening datagram socket"); 33 exit(1); 34 } 35 /* 36 * Construct name, with no wildcards, of the socket to send to. 37 * Getnostbyname() returns a structure including the network address 38 * of the specified host. The port number is taken from the command 39 * line. 40 */ 41 hp = gethostbyname(argv[1]); 42 if (hp == 0) { 43 fprintf(stderr, "%s: unknown host\n", argv[1]); 44 exit(2); 45 } 46 bcopy(hp->h_addr, &name.sin_addr, hp->h_length); 47 name.sin_family = AF_INET; 48 name.sin_port = htons(atoi(argv[2])); 49 /* Send message. */ 50 if (sendto(sock, DATA, sizeof(DATA), 0, &name, sizeof(name)) < 0) 51 perror("sending datagram message"); 52 close(sock); 53 } 54