Create a network service that sits on TCP port 12321, which accepts connections on that port, and which echoes complete lines (using a carriage-return/line-feed sequence as line separator) back to clients. No error handling is required. For the purposes of testing, it is only necessary to support connections from localhost (127.0.0.1 or perhaps ::1). Logging of connection information to standard output is recommended.

The implementation must be able to handle simultaneous connections from multiple clients. A multi-threaded or multi-process solution may be used. Each connection must be able to echo more than a single line.

The implementation must not stop responding to other clients if one client sends a partial line or stops reading responses.

package main
 
import (
	"fmt"
	"net"
	"bufio"
)
 
func echo(s net.Conn, i int) {
	defer s.Close();
 
	fmt.Printf("%d: %v <-> %v\n", i, s.LocalAddr(), s.RemoteAddr())
	b := bufio.NewReader(s)
	for {
		line, e := b.ReadBytes('\n')
		if e != nil {
			break
		}
		s.Write(line)
	}
	fmt.Printf("%d: closed\n", i)
}
 
func main() {
	l, e := net.Listen("tcp", ":12321")
	for i := 0; e == nil; i++ {
		var s net.Conn
		s, e = l.Accept()
		go echo(s, i)
	}
}