#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/time.h>

int sock;

int main(void) {
    struct sockaddr_in sa;
    int len = sizeof(sa);
    pthread_t receiver, sender;
    
    memset(&sa, 0, sizeof(sa));
    
    sock = socket(PF_INET, SOCK_DGRAM, 0);
    sa.sin_port = htons(12388);
    sa.sin_family = PF_INET;
    bind(sock, (struct sockaddr *)&sa, len);
    
    while(1) {
        char buf[32];
        int r;
        r = recvfrom(sock, buf, 32, 0, (struct sockaddr *)&sa, &len);
        if(sendto(sock, buf, r, 0, (struct sockaddr *)&sa, len) == -1)
            perror("sendto");
    }
}