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

int sock;

struct ts_pkt {
    struct timeval tv;
    char rsvd[32 - sizeof(struct timeval)];
};

void *receiverThread(void *arg) {
    int i = 100;
    struct ts_pkt ts;
    struct timeval tv;
    float delay;
    while(i--) {
        int r = recv(sock, &ts, sizeof(ts), 0);
        perror("recv");
        gettimeofday(&tv, NULL);
        delay = tv.tv_sec - ts.tv.tv_sec + ((tv.tv_usec - tv.tv_usec) / 1000000);
        printf("received: %d %d %d %f\n", r, ts.tv.tv_sec, ts.tv.tv_usec, delay);
    }
}

void *senderThread(void *arg) {
    int i = 100;
    struct ts_pkt ts;
    int len = 64;
    while(i--) {
        gettimeofday(&ts.tv, NULL);
        send(sock, &ts, sizeof(ts), 0);
        printf("%d %d\n", ts.tv.tv_sec, ts.tv.tv_usec);
        usleep(20000);
    }
}

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");
    }
}