/*Сервер должен быть запущен в 1-ой консоли */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <errno.h>
#define PORT 6969
#define BUFSIZE 16
int sock;
struct sockaddr_in addr;
char buf[BUFSIZE];
int bytes_read, total = 0;

int main() {
sock = socket(AF_INET, SOCK_DGRAM, 0);
addr.sin_family = AF_INET;
addr.sin_port = htons(PORT);
addr.sin_addr.s_addr = htonl(INADDR_ANY);
bind(sock, (struct sockaddr *)&addr, sizeof(addr));

while(1) {
bytes_read = recvfrom(sock, buf, BUFSIZE, 0, NULL, NULL);
total = total + bytes_read;
buf[bytes_read] = '\0';
fprintf(stdout, buf);fflush(stdout);
if (total>BUFSIZE) break;
}
printf("\nTotal %d bytes received", total);
return 0;
}
/* Клиент должен быть запущен во 2-ой консоли */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#define PORT 6969
char ss[]={"Hello world"};
int sock;
struct sockaddr_in addr;

int main() {
sock = socket(AF_INET, SOCK_DGRAM, 0);
addr.sin_family = AF_INET;
addr.sin_port = htons(PORT);
addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
connect(sock, (struct sockaddr *)&addr, sizeof(addr));
send(sock, ss, strlen(ss), 0);
close(sock);
return 0;
}