UDP

udp.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

void server(void) {
	int s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if(s < 0) {
		perror("socket");
		exit(1);
	}
	
	struct sockaddr_in server;
	server.sin_family = AF_INET;
	server.sin_addr.s_addr = INADDR_ANY;
	server.sin_port = htons(8888);
	
	if(bind(s, (struct sockaddr *)&server, sizeof(server)) < 0) {
		perror("bind");
		exit(1);
	}
	
	while(1) {
		char r = 0;
		
		if(recv(s, &r, sizeof(r), 0) < 0) {
			perror("recv");
			exit(1);
		}
		
		printf("%c", r);
	}
	
	close(s);
}

void client(void) {
	int s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if(s < 0) {
		perror("socket");
		exit(1);
	}
	
	struct sockaddr_in server;
	server.sin_family = AF_INET;
	server.sin_addr.s_addr = inet_addr("127.0.0.1");
	server.sin_port = htons(8888);
	
	while(1) {
		if(sendto(s, "x", 1, 0, (struct sockaddr *)&server, sizeof(server)) < 0) {
			perror("sendto");
			exit(1);
		}
	}
	
	close(s);
}

int main(void) {
	if(fork() == 0) server();
	else client();
	
	return 0;
}