go-tcp-echo-service.go

package main

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"net"
	"time"
	"strconv"
	"strings"
)

func main() {
	log.SetFlags(log.LstdFlags | log.Lmicroseconds)
	listener, err := net.Listen("tcp", ":9876")
	if err != nil {
		log.Fatalf("Failed to listen: %v", err)
	}
	defer listener.Close()
	log.Printf("TCP Echo Server listening on :9876 at epoch ms: %d", time.Now().UnixMilli())
	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Printf("Failed to accept connection: %v", err)
			continue
		}
		tcpConn, ok := conn.(*net.TCPConn)
		if ok {
			tcpConn.SetNoDelay(true)
		}
		go handleConnection(conn)
	}
}

func handleConnection(conn net.Conn) {
	defer conn.Close()
	remoteAddr := conn.RemoteAddr().String()
	log.Printf("New connection from %s at epoch ms: %d", remoteAddr, time.Now().UnixMilli())
	reader := bufio.NewReader(conn)
	for {
		data, err := reader.ReadString('\n')
		if err != nil {
			if err != io.EOF {
				log.Printf("Error reading from connection: %v", err)
			}
			return
		}
		nowMs := time.Now().UnixMilli()
		dataMs, atolErr := strconv.ParseInt(strings.TrimSpace(data), 10, 64)
		if atolErr != nil {
			fmt.Println(atolErr)
			fmt.Printf("[%d] From %s: %s\n", nowMs, remoteAddr, data)
		} else {
				fmt.Printf("[%d] From %s: %d [%dms]\n", nowMs, remoteAddr, dataMs, dataMs-nowMs)
		}
		//_, err = conn.Write([]byte(strconv.FormatInt(nowMs,10)+"\n"))
		_, err = conn.Write([]byte(data))
		if err != nil {
			log.Printf("Error writing to connection: %v", err)
		return
		}
	}
}

tcp-time-sender-receiver-python.py

import socket
import time

HOST = 'localhost'
PORT = 8080

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((HOST, PORT))
    s.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
    for i in range(10):
        current_time = int(time.time() * 1000)
        s.sendall(str(current_time).encode() + b'\n')
        print(f"Sent: {current_time} ms")

        server_time = s.recv(1024).strip().decode()
        server_time_int = int(server_time)
        received_time = int(time.time() * 1000)
        print(f"Receive time: {received_time} ms [{(received_time-current_time)/2} ms]")

        time.sleep(1)