UDP latency test (Based on https://www.abc.se/~m6695/udp.html)

common.h

#ifndef _COMMON_H

#define MAX_IP_LEN 16
#define MAX_TIME_LEN 32
#define MAX_DATA_LEN 64
/* 6ms */
#define MAX_LATENCY (60 * 1000)

typedef struct _packet {
    unsigned long long sid;
    unsigned long long ts;
    char msg[MAX_DATA_LEN];
} packet;

char *microsecond2time(char *buf, unsigned long long ts)
{
    unsigned long long sec = ts / 1000 / 1000;
    unsigned long long msec = (ts - sec * 1000 * 1000) / 1000;
    unsigned long long usec = (ts - sec * 1000 * 1000) % 1000;
    char time[MAX_TIME_LEN] = { 0x0 };
    struct tm *ptm = NULL;

    if (NULL == buf) {
        return NULL;
    }

    ptm = localtime((time_t *)&sec);
    strftime(time, MAX_TIME_LEN, "%Y-%m-%d %H:%M:%S", ptm);
    sprintf(buf, "[%s:%03d:%03d]", time, msec, usec);

    return buf;
}

#endif

Makefile

CC = gcc
CFLAGS = -O2 -g -Wall
INSTALL_DIR = /usr/bin

.PHONY: clean install uninstall

all: server client

server: udp-server.c
	$(CC) udp-server.c -o udp-server

client: udp-client.c
	$(CC) udp-client.c -o udp-client

clean:
	rm -f *.o udp-server udp-client

install: server client
	cp -f udp-server udp-client $(INSTALL_DIR)/

uninstall:
	rm -f $(INSTALL_DIR)/udp-server $(INSTALL_DIR)/udp-client

udp-client.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/time.h>
#include <arpa/inet.h>
#include "common.h"

static void print_help(const char *program)
{
    printf("Version: %s %s\n", __DATE__,  __TIME__);
    printf("Usage: %s <ip> [port]\n", program);
    printf("  ip          server IP for connecting\n");
    printf("  port        UDP port for communicating (default is 2017)\n");
    printf("  -h, --help  display this help and exit\n");
    printf("\nExample:\n");
    printf("  %s 192.168.1.1\n", program);
    printf("  %s 192.168.1.1 2017\n", program);
}

int main(int argc, char *argv[])
{
    int s = 0; /* UDP socket descriptor */
    int port = 2017; /* UDP port (default) */
    unsigned long long sid = 0; /* UDP packet sequence id */
    char ip[MAX_IP_LEN] = ""; /* Server IP */
    packet pkt;
    struct sockaddr_in si;
    struct timeval tv;
    struct timezone tz;

    if (argc == 2) {
        if ((strcmp(argv[1], "-h") == 0) || (strcmp(argv[1], "--help") == 0)) {
            print_help(argv[0]);
            exit(0);
        } else {
            strncpy(ip, argv[1], MAX_IP_LEN); /* FIXME: verify ip address */
        }
    } else if (argc == 3) {
        strncpy(ip, argv[1], MAX_IP_LEN); /* FIXME: verify ip address */
        port = atoi(argv[2]); /* FIXME: verify port number */
    } else {
        print_help(argv[0]);
        exit(0);
    }

    if ((s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
        fprintf(stderr, "Failed to create socket\n");
        exit(1);
    }

    memset(&si, 0x0, sizeof(si));
    si.sin_family = AF_INET;
    si.sin_port = htons(port);
    if (inet_aton(ip, &si.sin_addr) == 0) {
        fprintf(stderr, "Failed to inet_aton with %s:%d\n", ip, port);
        exit(1);
    }

    while (1) {
        sid++;
        gettimeofday(&tv, &tz);
        memset(&pkt, 0x0, sizeof(pkt));
        pkt.sid = sid;
        pkt.ts = tv.tv_sec * 1000 * 1000 + tv.tv_usec;
        microsecond2time(pkt.msg, pkt.ts);
        sprintf(pkt.msg, "%s-[%08llu]", pkt.msg, sid);
        printf("%s\n", pkt.msg);
        if (sendto(s, &pkt, sizeof(pkt), 0, (struct sockaddr *)&si,\
                   sizeof(struct sockaddr_in)) == -1) {
            fprintf(stderr, "Failed to send [%s] to %s:%d\n", pkt.msg, ip, port);
            close(s);
            exit(1);
        }
    }

    close(s);

    return 0;
}

udp-server.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/time.h>
#include <arpa/inet.h>
#include "common.h"

static void print_help(const char *program)
{
    printf("Version: %s %s\n", __DATE__,  __TIME__);
    printf("Usage: %s [port]\n", program);
    printf("  port        UDP port for binding and listening (default is 2017)\n");
    printf("  -h, --help  display this help and exit\n");
    printf("\nExample:\n");
    printf("  %s\n", program);
    printf("  %s 2017\n", program);
}

int main(int argc, char *argv[])
{
    int s = 0; /* UDP socket descriptor */
    int port = 2017; /* UDP port */
    unsigned long long last_sid = 0;
    unsigned long long ts = 0;
    char time[MAX_TIME_LEN] = { 0x0 };
    socklen_t addrlen;
    struct sockaddr_in si_server, si_client;
    packet pkt;
    struct timeval tv;
    struct timezone tz;

    if (argc == 2) {
        if ((strcmp(argv[1], "-h") == 0) || (strcmp(argv[1], "--help") == 0)) {
            print_help(argv[0]);
            exit(0);
        } else {
            port = atoi(argv[2]); /* FIXME: verify port number */
        }
    } else if (argc != 1) {
        print_help(argv[0]);
        exit(0);
    }

    printf("Starting...\n");

    if ((s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
        fprintf(stderr, "Failed to create socket\n");
        exit(1);
    }

    memset(&si_server, 0x0, sizeof(si_server));
    si_server.sin_family = AF_INET;
    si_server.sin_port = htons(port);
    si_server.sin_addr.s_addr = htonl(INADDR_ANY);
    if (bind(s, (struct sockaddr *)&si_server, sizeof(struct sockaddr)) == -1) {
        fprintf(stderr, "Failed to bind with port %d\n", port);
        exit(1);
    }

    while (1) {
        memset(&pkt, 0x0, sizeof(pkt));
        if (recvfrom(s, &pkt, sizeof(pkt), 0, \
                    (struct sockaddr *)&si_client, &addrlen) == -1) {
            fprintf(stderr, "Failed to recvfrom\n");
            close(s);
            exit(1);
        }
        gettimeofday(&tv, &tz);
        memset(time, 0x0, sizeof(time));
        ts = tv.tv_sec * 1000 * 1000 + tv.tv_usec;
        microsecond2time(time, ts);
        printf("Received from [%s:%d]: %s\n", inet_ntoa(si_client.sin_addr), \
                ntohs(si_client.sin_port), pkt.msg);
        printf("Local time: %s\n", time);
        if (pkt.sid != (last_sid + 1)) {
            printf("Warning: missing sid, expected %llu but actually %llu\n", \
                    last_sid + 1, pkt.sid);
        }
        if (ts - pkt.ts > MAX_LATENCY) {
            printf("Warning: the latency %llu exceeds the threshold %llu(us)\n", \
                    ts - pkt.ts, MAX_LATENCY);
        }
        last_sid = pkt.sid;
    }

    close(s);

    return 0;
}