/*
* This program creates a datagram socket, binds a name to it, and
* then reads from the socket.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
main()
{
int sock, length;
struct sockaddr_in name;
char buf[1024];
/* Create a socket from which to read. */
sock = socket(AF_INET, SOCK_DGRAM, 0);
if (sock < 0) {
perror("opening datagram socket");
exit(1);
}
/* Create name with wildcards. */
name.sin_family = AF_INET;
name.sin_addr.s_addr = INADDR_ANY;
name.sin_port = 0;
if (bind(sock, (struct sockaddr *)&name, sizeof(name))) {
perror("binding datagram socket");
exit(1);
}
/* Find assigned port value and print it out. */
length = sizeof(name);
if (getsockname(sock, (struct sockaddr *)&name, &length)) {
perror("getting socket name");
exit(1);
}
printf("Socket has port #%d\n", ntohs(name.sin_port));
/* Read from the socket. */
if (read(sock, buf, 1024) < 0)
perror("receiving datagram packet");
printf("-->%s\n", buf);
close(sock);
}
/*
* recvfrom() can also be used in place of the read. recvfrom()
* provides an extra field for setting flags. More explanation
* is available in Understanding Socket Data Transfer.
*/