WebSocket

The WebSocket object provides the API for creating and managing a WebSocket connection to a server, as well as for sending and receiving data on the connection.

To construct a WebSocket, use the WebSocket() constructor.

Constructor

WebSocket(url[, protocols])

Returns a newly created WebSocket object.

Constants

Properties

WebSocket.binaryType

The binary data type used by the connection.

WebSocket.bufferedAmount Read only

The number of bytes of queued data.

WebSocket.extensions Read only

The extensions selected by the server.

WebSocket.onclose

An event listener to be called when the connection is closed.

WebSocket.onerror

An event listener to be called when an error occurs.

WebSocket.onmessage

An event listener to be called when a message is received from the server.

WebSocket.onopen

An event listener to be called when the connection is opened.

WebSocket.protocol Read only

The sub-protocol selected by the server.

WebSocket.readyState Read only

The current state of the connection.

WebSocket.url Read only

The absolute URL of the WebSocket.

Methods

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

Closes the connection.

WebSocket.send(data)

Enqueues data to be transmitted.

Events

Listen to these events using addEventListener() or by assigning an event listener to the oneventname property of this interface.

close

Fired when a connection with a WebSocket is closed.
Also available via the onclose property

error

Fired when a connection with a WebSockethas been closed because of an error, such as when some data couldn't be sent.
Also available via the onerror property.

message

Fired when data is received through a WebSocket.
Also available via the onmessage property.

open

Fired when a connection with a WebSocket is opened.
Also available via the onopen property.

Examples

// Create WebSocket connection.
const socket = new WebSocket('ws://localhost:8080');

// Connection opened
socket.addEventListener('open', function (event) {
    socket.send('Hello Server!');
});

// Listen for messages
socket.addEventListener('message', function (event) {
    console.log('Message from server ', event.data);
});

Specifications

Browser compatibility

See also

• Writing WebSocket client applications