nettest.go

package main

import (
	"fmt"
	"net"
	"sync/atomic"
	"time"
)

func main() {
	ln, err := net.Listen("tcp", ":8080")
	if err != nil {
		panic(err)
	}
	go func() {
		for {
			conn, err := ln.Accept()
			if err != nil {
				panic(err)
			}
			go func() {
				for {
					buff := make([]byte, 4)
					if _, err := conn.Read(buff); err != nil {
						panic(err)
					}
					time.Sleep(time.Millisecond * 200)
					if _, err := conn.Write(buff); err != nil {
						panic(err)
					}
				}
			}()
		}
	}()

	duration := int64(0)
	count := int64(0)
	connections := int64(0)

	go func() {
		for {
			for i := 0; i < 400; i++ {
				go func() {
					conn, err := net.Dial("tcp", "localhost:8080")
					if err != nil {
						panic(err)
					}

					atomic.AddInt64(&connections, 1)

					for {
						start := time.Now()

						buff := []byte{1, 2, 3, 4}
						if _, err := conn.Write(buff); err != nil {
							panic(err)
						}
						if _, err := conn.Read(buff); err != nil {
							panic(err)
						}

						atomic.AddInt64(&duration, int64(time.Since(start)))
						atomic.AddInt64(&count, 1)
					}
				}()

				time.Sleep(time.Millisecond)
			}

			time.Sleep(time.Second * 4)
		}
	}()

	for {
		time.Sleep(time.Second)

		d := atomic.SwapInt64(&duration, 0)
		c := atomic.SwapInt64(&count, 0)
		n := atomic.LoadInt64(&connections)

		if c > 0 {
			fmt.Printf("% 4d: %v (%d)\n", n, time.Duration(d/c), c)
		}
	}
}