A node.js module for websocket server and client
Latest commit 28835a2 Nov 14, 2016 @sitegui Patch release


Nodejs Websocket

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A nodejs module for websocket server and client

How to use it

Install with npm install nodejs-websocket or put all files in a folder called "nodejs-websocket", and:

var ws = require("nodejs-websocket")

// Scream server example: "hi" -> "HI!!!"
var server = ws.createServer(function (conn) {
    console.log("New connection")
    conn.on("text", function (str) {
        console.log("Received "+str)
    conn.on("close", function (code, reason) {
        console.log("Connection closed")

Se other examples inside the folder samples


The main object, returned by require("nodejs-websocket").

ws.createServer([options], [callback])

Returns a new Server object.

The options is an optional object that will be handed to net.createServer() to create an ordinary socket. If it has a property called "secure" with value true, tls.createServer() will be used instead.

To support protocols, the options object may have either of these properties:

  • validProtocols: an array of protocol names the server accepts. The server will pick the most preferred protocol in the client's list.
  • selectProtocol: a callback to resolve the protocol negotiation. This callback will be passed two parameters: the connection handling the handshake and the array of protocol names informed by the client, ordered by preference. It should return the resolved protocol, or empty if there is no agreement.

The callback is a function which is automatically added to the "connection" event.

ws.connect(URL, [options], [callback])

Returns a new Connection object, representing a websocket client connection

URL is a string with the format "ws://localhost:8000/chat" (the port can be omitted)

options is an object that will be passed to net.connect() (or tls.connect() if the protocol is "wss:"). The properties "host" and "port" will be read from the URL. The optional property extraHeaders will be used to add more headers to the HTTP handshake request. If present, it must be an object, like {'X-My-Header': 'value'}. The optional property protocols will be used in the handshake (as "Sec-WebSocket-Protocol" header) to allow the server to choose one of those values. If present, it must be an array of strings.

callback will be added as "connect" listener


Sets the minimum size of a pack of binary data to send in a single frame (default: 512kiB)


Set the maximum size the internal Buffer can grow (default: 2MiB) If at any time it stays bigger than this, the connection will be closed with code 1009 This is a security measure, to avoid memory attacks


The class that represents a websocket server, much like a HTTP server

server.listen(port, [host], [callback])

Starts accepting connections on a given port and host.

If the host is omitted, the server will accept connections directed to any IPv4 address (INADDR_ANY).

A port value of zero will assign a random port.

callback will be added as an listener for the 'listening' event.


Stops the server from accepting new connections and keeps existing connections. This function is asynchronous, the server is finally closed when all connections are ended and the server emits a 'close' event. The optional callback will be called once the 'close' event occurs.


The underlying socket, returned by net.createServer or tls.createServer


An Array with all connected clients. It's useful for broadcasting a message:

function broadcast(server, msg) {
    server.connections.forEach(function (conn) {

Event: 'listening()'

Emitted when the server has been bound after calling server.listen

Event: 'close()'

Emitted when the server closes. Note that if connections exist, this event is not emitted until all connections are completely ended.

Event: 'error(errObj)'

Emitted when an error occurs. The 'close' event will be called directly following this event.

Event: 'connection(conn)'

Emitted when a new connection is made successfully (after the handshake have been completed). conn is an instance of Connection


The class that represents a connection, either a client-created (accepted by a nodejs ws server) or client connection. The websocket protocol has two types of data frames: text and binary. Text frames are implemented as simple send function and receive event. Binary frames are implemented as streams: when you receive binary data, you get a ReadableStream; to send binary data, you must ask for a WritableStream and write into it. The binary data will be divided into frames and be sent over the socket.

You cannot send text data while sending binary data. If you try to do so, the connection will emit an "error" event

connection.sendText(str, [callback])

Sends a given string to the other side. You can't send text data in the middle of a binary transmission.

callback will be added as a listener to write operation over the socket


Asks the connection to begin transmitting binary data. Returns a WritableStream. The binary transmission will end when the WritableStream finishes (like when you call .end on it)

connection.sendBinary(data, [callback])

Sends a single chunk of binary data (like calling connection.beginBinary().end(data))

callback will be added as a listener to write operation over the socket

connection.send(data, [callback])

Sends a given string or Buffer to the other side. This is simply an alias for sendText() if data is a string or sendBinary() if the data is a Buffer.

callback will be added as a listener to write operation over the socket


Sends a ping with optional payload

connection.close([code, [reason]])

Starts the closing handshake (sends a close frame)


The underlying net or tls socket


If the connection was accepted by a nodejs server, a reference to it will be saved here. null otherwise


One of these constants, representing the current state of the connection. Only an open connection can be used to send/receive data.

  • connection.CONNECTING (waiting for handshake completion)
  • connection.OPEN
  • connection.CLOSING (waiting for the answer to a close frame)
  • connection.CLOSED


Stores the OutStream object returned by connection.beginBinary(). null if there is no current binary data beeing sent.


For a connection accepted by a server, it is a string representing the path to which the connection was made (example: "/chat"). null otherwise


Read only map of header names and values. Header names are lower-cased


Array of protocols requested by the client. If no protocols were requested, it will be an empty array.

Additional resources on websocket subprotocols:


The protocol agreed for this connection, if any. It will be an element of connection.protocols.

Event: 'close(code, reason)'

Emitted when the connection is closed by any side

Event: 'error(err)'

Emitted in case of error (like trying to send text data while still sending binary data). In case of an invalid handshake response will also be emited.

Event: 'text(str)'

Emitted when a text is received. str is a string

Event: 'binary(inStream)'

Emitted when the beginning of binary data is received. inStream is a ReadableStream:

var server = ws.createServer(function (conn) {
    console.log("New connection")
    conn.on("binary", function (inStream) {
        // Empty buffer for collecting binary data
        var data = new Buffer(0)
        // Read chunks of binary data and add to the buffer
        inStream.on("readable", function () {
            var newData = inStream.read()
            if (newData)
                data = Buffer.concat([data, newData], data.length+newData.length)
        inStream.on("end", function () {
            console.log("Received " + data.length + " bytes of binary data")
    conn.on("close", function (code, reason) {
        console.log("Connection closed")

Event: 'connect()'

Emitted when the connection is fully established (after the handshake)

Event: 'pong(data)'

Emitted when a pong is received, usually after a ping was sent. data is the pong payload, as a string