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

#define PACKETS 10000

int sock;

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

static inline double delta(struct timeval a, struct timeval b)
{
      if (a.tv_usec & b.tv_usec)  {
              a.tv_sec--;
              a.tv_usec += 1000000;
      }
      return a.tv_sec-b.tv_sec + (a.tv_usec-b.tv_usec)/1000000.0;
}

void *receiverThread(void *arg) {
    struct ts_pkt ts;
    struct timeval tv;
    float delay;
    while(1) {
        pthread_testcancel();
        if(recv(sock, &ts, sizeof(ts), 0) == -1)
            perror("recv");
        gettimeofday(&tv, NULL);
        printf("%f\n", delta(tv, ts.tv));
    }
}

void *senderThread(void *arg) {
    int i = PACKETS;
    struct ts_pkt ts;
    while(i--) {
        gettimeofday(&ts.tv, NULL);
        send(sock, &ts, sizeof(ts), 0);
        usleep(15000);
    }
}

int main(void) {
    struct sockaddr_in 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;
    sa.sin_addr.s_addr = inet_addr("127.0.0.1");
    connect(sock, (struct sockaddr *)&sa, sizeof(sa));
    
    pthread_create(&receiver, 0, receiverThread, 0);
    pthread_create(&sender, 0, senderThread, 0);
    pthread_join(sender, 0);
    pthread_cancel(receiver);
}