golang unix domain socket

client.go

package main

import (
	"io"
	"log"
	"net"
	"time"
)

func reader(r io.Reader) {
	buf := make([]byte, 1024)
	for {
		n, err := r.Read(buf[:])
		if err != nil {
			return
		}
		println("Client got:", string(buf[0:n]))
	}
}

func main() {
	c, err := net.Dial("unix", "/tmp/go.sock")
	if err != nil {
		log.Fatal("Dial error", err)
	}
	defer c.Close()

	go reader(c)
	for {
		msg := "hi"
		_, err := c.Write([]byte(msg))
		if err != nil {
			log.Fatal("Write error:", err)
			break
		}
		println("Client sent:", msg)
		time.Sleep(1e9)
	}
}

server.go

package main

import (
	"log"
	"net"
	"os"
	"os/signal"
	"syscall"
)

func echoServer(c net.Conn) {
	for {
		buf := make([]byte, 512)
		nr, err := c.Read(buf)
		if err != nil {
			return
		}

		data := buf[0:nr]
		println("Server got:", string(data))
		_, err = c.Write(data)
		if err != nil {
			log.Fatal("Writing client error: ", err)
		}
	}
}

func main() {
	log.Println("Starting echo server")
	ln, err := net.Listen("unix", "/tmp/go.sock")
	if err != nil {
		log.Fatal("Listen error: ", err)
	}

	sigc := make(chan os.Signal, 1)
	signal.Notify(sigc, os.Interrupt, syscall.SIGTERM)
	go func(ln net.Listener, c chan os.Signal) {
		sig := <-c
		log.Printf("Caught signal %s: shutting down.", sig)
		ln.Close()
		os.Exit(0)
	}(ln, sigc)

	for {
		fd, err := ln.Accept()
		if err != nil {
			log.Fatal("Accept error: ", err)
		}

		go echoServer(fd)
	}
}

learn

When I exit without the ln.Close() being called, then restart results in Listen error: listen unix .sock: bind: address already in use exit status 1. Anyway to handle this?

When you call ln.Close() this function remove socket file /tmp/go.sock. You can stop your program, remove this file manually and start program.

// So, servers should unlink the socket pathname prior to binding it.
// https://troydhanson.github.io/network/Unix_domain_sockets.html
syscall.unlink("/tmp/go.sock")
log.Println("Starting echo server")
ln, err := net.Listen("unix", "/tmp/go.sock")

How can we unit test this ? I don't find any reference to get started with unit testing of unix domain sockets.

// So, servers should unlink the socket pathname prior to binding it.
// https://troydhanson.github.io/network/Unix_domain_sockets.html
syscall.unlink("/tmp/go.sock")
log.Println("Starting echo server")
ln, err := net.Listen("unix", "/tmp/go.sock")

unlink should be Unlink ( capitalize u).