golang socket server & client ping-pong demo

client.go

package main

import (
	"os"
    	"log"
	"net"
	"strconv"
	"strings"
)

const (
	message       = "Ping"
	StopCharacter = "\r\n\r\n"
)

func SocketClient(ip string, port int) {
	addr := strings.Join([]string{ip, strconv.Itoa(port)}, ":")
	conn, err := net.Dial("tcp", addr)

	if err != nil {
		log.Fatalln(err)
		os.Exit(1)
	}
	
	defer conn.Close()

	conn.Write([]byte(message))
	conn.Write([]byte(StopCharacter))
	log.Printf("Send: %s", message)

	buff := make([]byte, 1024)
	n, _ := conn.Read(buff)
	log.Printf("Receive: %s", buff[:n])

}

func main() {

	var (
		ip   = "127.0.0.1"
		port = 3333
	)

	SocketClient(ip, port)

}

server.go

package main

import (
    "bufio"
	"io"
	"log"
	"net"
	"os"
	"strconv"
	"strings"
)

const (
	Message       = "Pong"
	StopCharacter = "\r\n\r\n"
)

func SocketServer(port int) {

	listen, err := net.Listen("tcp4", ":"+strconv.Itoa(port))
	
	if err != nil {
		log.Fatalf("Socket listen port %d failed,%s", port, err)
		os.Exit(1)
	}
	
	defer listen.Close()
	
	log.Printf("Begin listen port: %d", port)

	for {
		conn, err := listen.Accept()
		if err != nil {
			log.Fatalln(err)
			continue
		}
		go handler(conn)
	}

}

func handler(conn net.Conn) {

	defer conn.Close()

	var (
		buf = make([]byte, 1024)
		r   = bufio.NewReader(conn)
		w   = bufio.NewWriter(conn)
	)

ILOOP:
	for {
		n, err := r.Read(buf)
		data := string(buf[:n])

		switch err {
		case io.EOF:
			break ILOOP
		case nil:
			log.Println("Receive:", data)
			if isTransportOver(data) {
				break ILOOP
			}

		default:
			log.Fatalf("Receive data failed:%s", err)
			return
		}

	}
	w.Write([]byte(Message))
	w.Flush()
	log.Printf("Send: %s", Message)

}

func isTransportOver(data string) (over bool) {
	over = strings.HasSuffix(data, "\r\n\r\n")
	return
}

func main() {

	port := 3333

	SocketServer(port)

}

What's does ILOOP mean in the code?

@cre8andctrl it breaks the outer for Loop, since writing only break; will only break the switch statement execution and not the the outer for loop

How to detect closed TCP connection when client disconnected?

Thanks for your gist! I think the defer listen.Close() action should be after err handle.

Revised, thanks a lot @you06

Thank you very much, your contribution helped me !

Verify Github on Galaxy. gid:853fCjKgvQfoCSEgaWbQeg