ws

The ws module provides a WebSocket client for JSH applications. It exposes a single WebSocket class built on top of the native Go WebSocket client.

Typical usage looks like this.

const { WebSocket } = require('ws');

WebSocket

Creates a WebSocket client connection.

Syntax

new WebSocket(url)

Parameters

• url String: WebSocket server address such as ws://host:port/path or wss://host:port/path.

If url is missing or is not a string, the constructor throws TypeError.

Properties

readyState values

• WebSocket.CONNECTING = 0
• WebSocket.OPEN = 1
• WebSocket.CLOSING = 2
• WebSocket.CLOSED = 3

Message type constants

• WebSocket.TextMessage = 1
• WebSocket.BinaryMessage = 2

send()

Sends a message to the server.

Syntax

ws.send(data)

Parameters

• data String: Message text to send.

If the socket is not open, the module emits an error event.

Usage example

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const { WebSocket } = require('ws');

const ws = new WebSocket('ws://127.0.0.1:8080');
ws.on('open', () => {
    ws.send('Hello, server');
});

close()

Closes the current connection.

Syntax

ws.close()

Calling close() transitions the socket through CLOSING to CLOSED and emits close.

Events

WebSocket extends EventEmitter and supports normal event-listener patterns such as on() and addListener().

open

Emitted after the client successfully connects.

ws.on('open', () => {
    console.println('connected');
});

close

Emitted when the connection closes.

ws.on('close', () => {
    console.println('closed');
});

message

Emitted when a message arrives from the server.

The callback receives an event-like object with these fields.

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const { WebSocket } = require('ws');

const ws = new WebSocket('ws://127.0.0.1:8080');
ws.on('message', (evt) => {
    console.println(evt.data);
});

error

Emitted when connection or send operations fail.

ws.on('error', (err) => {
    console.println(err.message);
});

Usage example

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const { WebSocket } = require('ws');

const ws = new WebSocket('ws://127.0.0.1:8080');

ws.on('open', () => {
    console.println('websocket open');
    ws.send('test message');
});

ws.on('message', (evt) => {
    console.println(evt.data);
    ws.close();
});

ws.on('close', () => {
    console.println('websocket closed');
});

Behavior notes

• The module implements a WebSocket client only. It does not provide server-side upgrade handling.
• Connection establishment is started asynchronously from the constructor.
• Connection failures are reported through the error event.
• Incoming messages may be text or binary, but the JavaScript send() method is intended for text message usage.