udp send

#include <sys/socket.h>#include <sys/types.h>#include <netinet/in.h>#include <pthread.h>#include <sys/time.h>#include <sys/ioctl.h>#include <linux/rtc.h>#include <unistd.h>#include <fcntl.h>#include <stdio.h>#define PACKETS 50000int sock;struct timeval start;FILE *logfile;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);        fprintf(logfile, "%f %f\n", delta(tv, start), delta(tv, ts.tv));    }}void *senderThread(void *arg) {    int rtc;    unsigned long ticks;    int i = PACKETS;    struct ts_pkt ts;        rtc = open("/dev/rtc", O_RDONLY);    if(rtc == -1) {        perror("/dev/rtc");        pthread_exit(NULL);    }    ticks = 64;    ioctl(rtc, RTC_PIE_ON, 0);    if(ioctl(rtc, RTC_IRQP_SET, ticks) == -1) {        perror("/dev/rtc");        pthread_exit(NULL);    }    while(i--) {        read(rtc, &ticks, sizeof(ticks));        ticks >>=8;        while(ticks--) {            gettimeofday(&ts.tv, NULL);            send(sock, &ts, sizeof(ts), 0);        }    }    ioctl(rtc, RTC_PIE_OFF, 0);    close(rtc);}int main(int argc, char **argv) {    struct sockaddr_in sa;    pthread_t receiver, sender;    FILE *gnuplot;        if(argc < 3) {      printf("Syntax: udp-send [ip] [file]\n");      exit(0);    }    memset(&sa, 0, sizeof(sa));    logfile = fopen(argv[2], "w");    sock = socket(PF_INET, SOCK_DGRAM, 0);    sa.sin_port = htons(12388);    sa.sin_family = PF_INET;    sa.sin_addr.s_addr = inet_addr(argv[1]);    connect(sock, (struct sockaddr *)&sa, sizeof(sa));        gettimeofday(&start, NULL);    pthread_create(&receiver, 0, receiverThread, 0);    pthread_create(&sender, 0, senderThread, 0);    pthread_join(sender, 0);    sleep(3);    pthread_cancel(receiver);    fclose(logfile);    gnuplot = popen("/usr/bin/gnuplot", "w");    fprintf(gnuplot, "set terminal png large size 1280,1024\n");    fprintf(gnuplot, "set output '%s.png'\n", argv[2]);    fprintf(gnuplot, "set title 'UDP RTT Timing at 64pps'\n");    fprintf(gnuplot, "set xlabel 'Time in Seconds'\n");    fprintf(gnuplot, "set ylabel 'UDP Response in Seconds'\n");    fprintf(gnuplot, "plot '%s' title 'UDP Response Time'\n", argv[2]);    fflush(gnuplot);    pclose(gnuplot);}