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.

Note: This feature is available in Web Workers

Constructor

WebSocket(url[, protocols]): Returns a newly created WebSocket object.

Constants

Constant	Value
`WebSocket.CONNECTING`	`0`
`WebSocket.OPEN`	`1`
`WebSocket.CLOSING`	`2`
`WebSocket.CLOSED`	`3`

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 WebSocket has 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

Specification
HTML Standard (HTML) # the-websocket-interface

Browser compatibility

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