/*
* This program fragment sends a datagram to a receiver whose
* name is retrieved from the command line arguments. The form
* of the command line is dgramsend hostname portnumber.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#define DATA "The sea is calm tonight, the tide is full..."
main(argc, argv)
int argc;
char *argv[];
{
int sock;
struct sockaddr_in name;
struct hostent *hp, *gethostbyname();
/* Create a socket on which to send. */
sock = socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) {
perror("opening datagram socket");
exit(1);
}
/*
* Construct name, with no wildcards, of the socket to send to.
* gethostbyname() returns a structure including the network
* address of the specified host. The port number is taken
* from the command line.
*/
hp = gethostbyname(argv[1]);
if (hp == 0) {
fprintf(stderr, "%s: unknown host", argv[1]);
exit(2);
}
bcopy(hp->h_addr, &name.sin_addr, hp->h_length);
name.sin_family = AF_INET;
name.sin_len = sizeof(name);
name.sin_port = htons(atoi(argv[2]));
/* Send message. */
if (sendto(sock, DATA, sizeof(DATA), 0,
(struct sockaddr *)&name,
sizeof(name)) < 0)
perror("sending datagram message");
close(sock);
}