Writing a Websocket Chat in Go

package chat

import (
	"log"
	"net/http"
)

// Run starts a new chat server with 4 chat rooms, listening on port 8080
func Run() {

	fs := http.FileServer(http.Dir("static"))
	http.Handle("/", fs)

	for _, name := range []string{"arduino", "java", "go", "scala"} {
		r := NewRoom(name)
		http.Handle("/chat/"+name, r)
		go r.Run()
	}

	log.Printf("starting chat server on port 8080")

	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatal("starting server failed: ", err)
	}

}

package chat

import (
	"log"
	"net/http"

	"github.com/gorilla/websocket"
)

const (
	socketBufferSize  = 1024
	messageBufferSize = 256
)

// Room represents a single chat room
type Room struct {
	forward chan []byte

	join chan *Chatter

	leave chan *Chatter

	chatters map[*Chatter]bool

	topic string
}

var upgrader = &websocket.Upgrader{
	ReadBufferSize:  socketBufferSize,
	WriteBufferSize: socketBufferSize,
	CheckOrigin: func(r *http.Request) bool {
		return true
	},
}

func (r *Room) ServeHTTP(w http.ResponseWriter, req *http.Request) {
	socket, err := upgrader.Upgrade(w, req, nil)
	if err != nil {
		log.Fatal("serving http failed ", err)
		return
	}

	chatter := &Chatter{
		socket: socket,
		send:   make(chan []byte, messageBufferSize),
		room:   r,
	}

	r.join <- chatter
	defer func() {
		r.leave <- chatter
	}()
	go chatter.write()
	chatter.read()
}

// NewRoom creates a new chat room
func NewRoom(topic string) *Room {
	return &Room{
		forward:  make(chan []byte),
		join:     make(chan *Chatter),
		leave:    make(chan *Chatter),
		chatters: make(map[*Chatter]bool),
		topic:    topic,
	}
}

// Run initializes a chat room
func (r *Room) Run() {
	log.Printf("running chat room %v", r.topic)
	for {
		select {
		case chatter := <-r.join:
			log.Printf("new chatter in room %v", r.topic)
			r.chatters[chatter] = true
		case chatter := <-r.leave:
			log.Printf("chatter leaving room %v", r.topic)
			delete(r.chatters, chatter)
			close(chatter.send)
		case msg := <-r.forward:
			data := FromJSON(msg)
			log.Printf("chatter '%v' writing message to room %v, message: %v", data.Sender, r.topic, data.Message)
			for chatter := range r.chatters {
				select {
				case chatter.send <- msg:
				default:
					delete(r.chatters, chatter)
					close(chatter.send)
				}
			}
		}
	}
}

package chat

import "github.com/gorilla/websocket"

// Chatter represents a single Chatter
type Chatter struct {
	socket *websocket.Conn
	send   chan []byte
	room   *Room
}

func (c *Chatter) read() {
	for {
		if _, msg, err := c.socket.ReadMessage(); err == nil {
			c.room.forward <- msg
		} else {
			break
		}
	}
	c.socket.Close()
}

func (c *Chatter) write() {
	for msg := range c.send {
		if err := c.socket.WriteMessage(websocket.TextMessage, msg); err != nil {
			break
		}
	}
	c.socket.Close()
}

package chat

import (
	"encoding/json"
)

// Message represents a chat message
type Message struct {
	Message string `json:"message"`
	Sender  string `json:"sender"`
	Created string `json:"created"`
}

// FromJSON created a new Message struct from given JSON
func FromJSON(jsonInput []byte) (message *Message) {
	json.Unmarshal(jsonInput, &message)
	return
}

var wsocket;
var serviceLocation = "ws://0.0.0.0:8080/chat/";
var $nickName;
var $message;
var $chatWindow;
var room = '';

function onMessageReceived(evt) {
    var msg = JSON.parse(evt.data); // native API
    var $messageLine = $('<tr><td class="received">' + msg.received
            + '</td><td class="user label label-info">' + msg.sender
            + '</td><td class="message badge">' + msg.message
            + '</td></tr>');
    $chatWindow.append($messageLine);
}
function sendMessage() {
    var msg = '{"message":"' + $message.val() + '", "sender":"'
            + $nickName.val() + '", "received":""}';
    wsocket.send(msg);
    $message.val('').focus();
}

function connectToChatserver() {
    room = $('#chatroom option:selected').val();
    wsocket = new WebSocket(serviceLocation + room);
    wsocket.onmessage = onMessageReceived;
}

function leaveRoom() {
    wsocket.close();
    $chatWindow.empty();
    $('.chat-wrapper').hide();
    $('.chat-signin').show();
    $nickName.focus();
}

$(document).ready(function() {
    $nickName = $('#nickname');
    $message = $('#message');
    $chatWindow = $('#response');
    $('.chat-wrapper').hide();
    $nickName.focus();

    $('#enterRoom').click(function(evt) {
        evt.preventDefault();
        connectToChatserver();
        $('.chat-wrapper h2').text('Chat # '+$nickName.val() + "@" + room);
        $('.chat-signin').hide();
        $('.chat-wrapper').show();
        $message.focus();
    });
    $('#do-chat').submit(function(evt) {
        evt.preventDefault();
        sendMessage()
    });

    $('#leave-room').click(function(){
        leaveRoom();
    });
});

<div class="container chat-signin">
	<form class="form-signin">
		<h2 class="form-signin-heading">Chat sign in</h2>
		<label for="nickname">Nickname</label> <input type="text"
			class="input-block-level" placeholder="Nickname" id="nickname">
		<div class="btn-group">
			<label for="chatroom">Chatroom</label> <select size="1"
				id="chatroom">
				<option>arduino</option>
				<option>java</option>
				<option>go</option>
				<option>scala</option>
			</select>
		</div>
		<button class="btn btn-large btn-primary" type="submit"
			id="enterRoom">Sign in</button>
	</form>
</div>

<div class="container chat-wrapper">
	<form id="do-chat">
		<h2 class="alert alert-success"></h2>
		<table id="response" class="table table-bordered"></table>
		<fieldset>
			<legend>Enter your message..</legend>
			<div class="controls">
				<input type="text" class="input-block-level" placeholder="Your message..." id="message" style="height:60px"/>
				<input type="submit" class="btn btn-large btn-block btn-primary"
					value="Send message" />
				<button class="btn btn-large btn-block" type="button" id="leave-room">Leave
					room</button>
			</div>
		</fieldset>
	</form>
</div>