func newListener(proto, addr string, bufferRequests bool) (net.Listener, error) {
	if bufferRequests {
		return listenbuffer.NewListenBuffer(proto, addr, activationLock)
	}

	return net.Listen(proto, addr)
}

func NewTcpSocket(addr string, tlsConfig *tls.Config, activate chan struct{}) (net.Listener, error) {
	l, err := listenbuffer.NewListenBuffer("tcp", addr, activate)
	if err != nil {
		return nil, err
	}
	if tlsConfig != nil {
		tlsConfig.NextProtos = []string{"http/1.1"}
		l = tls.NewListener(l, tlsConfig)
	}
	return l, nil
}

func NewTcpSocket(addr string, config *tlsConfig) (net.Listener, error) {
	l, err := listenbuffer.NewListenBuffer("tcp", addr, activationLock)
	if err != nil {
		return nil, err
	}
	if config != nil {
		if l, err = setupTls(l, config); err != nil {
			return nil, err
		}
	}
	return l, nil
}

func newTCPSocket(addr string, config *TLSConfig, activate <-chan struct{}) (net.Listener, error) {
	l, err := listenbuffer.NewListenBuffer("tcp", addr, activate)
	if err != nil {
		return nil, err
	}
	if config != nil {
		if l, err = setupTLS(l, config); err != nil {
			return nil, err
		}
	}
	return l, nil
}

func newUnixSocket(path, group string, activate <-chan struct{}) (net.Listener, error) {
	if err := syscall.Unlink(path); err != nil && !os.IsNotExist(err) {
		return nil, err
	}
	mask := syscall.Umask(0777)
	defer syscall.Umask(mask)
	l, err := listenbuffer.NewListenBuffer("unix", path, activate)
	if err != nil {
		return nil, err
	}
	if err := setSocketGroup(path, group); err != nil {
		l.Close()
		return nil, err
	}
	if err := os.Chmod(path, 0660); err != nil {
		l.Close()
		return nil, err
	}
	return l, nil
}

// ListenAndServe sets up the required http.Server and gets it listening for
// each addr passed in and does protocol specific checking.
func ListenAndServe(proto, addr string, job *engine.Job) error {
	var l net.Listener
	r, err := createRouter(job.Eng, job.GetenvBool("Logging"), job.GetenvBool("EnableCors"), job.Getenv("Version"))
	if err != nil {
		return err
	}

	if proto == "fd" {
		return ServeFd(addr, r)
	}

	if proto == "unix" {
		if err := syscall.Unlink(addr); err != nil && !os.IsNotExist(err) {
			return err
		}
	}

	var oldmask int
	if proto == "unix" {
		oldmask = syscall.Umask(0777)
	}

	if job.GetenvBool("BufferRequests") {
		l, err = listenbuffer.NewListenBuffer(proto, addr, activationLock)
	} else {
		l, err = net.Listen(proto, addr)
	}

	if proto == "unix" {
		syscall.Umask(oldmask)
	}
	if err != nil {
		return err
	}

	if proto != "unix" && (job.GetenvBool("Tls") || job.GetenvBool("TlsVerify")) {
		tlsCert := job.Getenv("TlsCert")
		tlsKey := job.Getenv("TlsKey")
		cert, err := tls.LoadX509KeyPair(tlsCert, tlsKey)
		if err != nil {
			return fmt.Errorf("Couldn't load X509 key pair (%s, %s): %s. Key encrypted?",
				tlsCert, tlsKey, err)
		}
		tlsConfig := &tls.Config{
			NextProtos:   []string{"http/1.1"},
			Certificates: []tls.Certificate{cert},
		}
		if job.GetenvBool("TlsVerify") {
			certPool := x509.NewCertPool()
			file, err := ioutil.ReadFile(job.Getenv("TlsCa"))
			if err != nil {
				return fmt.Errorf("Couldn't read CA certificate: %s", err)
			}
			certPool.AppendCertsFromPEM(file)

			tlsConfig.ClientAuth = tls.RequireAndVerifyClientCert
			tlsConfig.ClientCAs = certPool
		}
		l = tls.NewListener(l, tlsConfig)
	}

	// Basic error and sanity checking
	switch proto {
	case "tcp":
		if !strings.HasPrefix(addr, "127.0.0.1") && !job.GetenvBool("TlsVerify") {
			log.Println("/!\\ DON'T BIND ON ANOTHER IP ADDRESS THAN 127.0.0.1 IF YOU DON'T KNOW WHAT YOU'RE DOING /!\\")
		}
	case "unix":
		socketGroup := job.Getenv("SocketGroup")
		if socketGroup != "" {
			if err := changeGroup(addr, socketGroup); err != nil {
				if socketGroup == "docker" {
					// if the user hasn't explicitly specified the group ownership, don't fail on errors.
					utils.Debugf("Warning: could not chgrp %s to docker: %s", addr, err.Error())
				} else {
					return err
				}
			}
		}
		if err := os.Chmod(addr, 0660); err != nil {
			return err
		}
	default:
		return fmt.Errorf("Invalid protocol format.")
	}

	httpSrv := http.Server{Addr: addr, Handler: r}
	return httpSrv.Serve(l)
}