UDP, Server and Client examples

06 Dec 2011

/*
 * udpserver.c
 *
 * UDP Server example
 */
 
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define pexit(s) ({perror(s); exit(EXIT_FAILURE);})

int main(int argc, char **argv)
{
#define BUFLEN 1000
        char buf[BUFLEN];
        int sock, error, clilen, bytes;
        struct sockaddr_in srv, cli; 
        
        if (argc < 2) {
                printf("Usage: %s PORT\n", argv[0]);
                exit(EXIT_FAILURE);
        }

        sock = socket(AF_INET, SOCK_DGRAM, 0);
        if (sock == -1)
                pexit("socket");


        memset(&srv, 0, sizeof(srv));
        srv.sin_family =  AF_INET;
        srv.sin_port = htons(atoi(argv[1]));
        srv.sin_addr.s_addr = htonl(INADDR_ANY);

        error = bind(sock, (struct sockaddr *)&srv, sizeof(srv));

        for (;;) {
               clilen = sizeof(cli);
               bytes = recvfrom(sock, buf, BUFLEN, 0, (struct sockaddr *)&cli,
                               &clilen);
               if (bytes == -1)
                       pexit("recvfrom");

               printf("received data from %s\n",
                               inet_ntoa(cli.sin_addr.s_addr));
               buf[bytes] = '\0';
               printf(">>%s<<\n", buf);
        }
        return 0;
} 

/*
 * udpclient.c
 *
 * UDP client example
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define pexit(s) ({perror(s); exit(EXIT_FAILURE);})

int main(int argc, char **argv)
{
        int sock, error, srvlen, bytes;
        struct sockaddr_in srv;
        
        if (argc <= 2) {
                printf("Usage: %s IP PORT\n", argv[0]);
                exit(EXIT_FAILURE);
        }

        sock = socket(AF_INET, SOCK_DGRAM, 0);
        if (sock == -1)
                pexit("socket");


        memset(&srv, 0, sizeof(srv));
        srv.sin_family =  AF_INET;
        srv.sin_port = htons(atoi(argv[2]));
        srv.sin_addr.s_addr = inet_addr(argv[1]);

        bytes = sendto(sock, "Hello World", strlen("Hello World"), 0,
                        (struct sockaddr *)&srv, sizeof(srv));
        if (bytes == -1)
                pexit("sendto");

        close(sock);

        return 0;
}