server.go

package main

import (
	"errors"
	"fmt"
	"log"
	"net"
	"net/http"
)

var ErrNoConnection = errors.New("no connection available")

type singleListener struct {
	conn net.Conn
	addr net.Addr
}

func newSingleListener(conn net.Conn, addr net.Addr) *singleListener {
	return &singleListener{
		conn: conn,
		addr: addr,
	}
}

func (s *singleListener) Accept() (net.Conn, error) {
	if s.conn == nil {
		return nil, ErrNoConnection
	}

	conn := s.conn
	s.conn = nil
	return conn, nil
}

func (s *singleListener) Close() error {
	s.conn = nil
	return nil
}

func (s *singleListener) Addr() net.Addr {
	return s.addr
}

func main() {
	listener, err := net.Listen("tcp", "127.0.0.1:1234")
	if err != nil {
		log.Fatalf("error listening: %s", err)
	}

	for {
		conn, err := listener.Accept()
		if err != nil {
			log.Fatalf("error accepting: %s", err)
		}

		log.Printf("accepted connection from %s", conn.RemoteAddr())

		mux := http.NewServeMux()
		mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
			// connection is available in mux
			body := fmt.Sprintf("this is dedicated server for %s", conn.RemoteAddr())
			w.Write([]byte(body))
		})

		server := &http.Server{
			Handler: mux,
		}

		err = server.Serve(newSingleListener(conn, listener.Addr()))
		if err != ErrNoConnection {
			log.Printf("error serving %s: %s", conn.RemoteAddr(), err)
		}

		log.Printf("finished serving connection from %s", conn.RemoteAddr())
	}
}