Electrum-Cash Web Socket

This package provides a configurable ElectrumSocket that works in both NodeJS and browser settings, with consistent behavior across various environments by default.

Features

the ElectrumSocket is a wrapper for a WebSocket with the following added features:

• Has promise-based and idempotent interfaces.
• Uses the debug package for configurable logging levels.
• Initial connections time out rather than linger in a stalled state.
• Can automatically suspend to save battery based on browser visibility and connectivity.

Usage

Imports

Before using this package, you need to import it:

import { ElectrumWebSocket } from '@electrum-cash/web-socket';

To properly handle all possible errors, also import the custom error types:

import type {
	SocketInternalError,
	SocketTimeoutError,
	SocketConnectionError,
	SocketWriteError,
} from '@electrum-cash/web-socket`;

Creating an ElectrumWebSocket

First, create an instance of the socket with:

// Create the web socket with default behavior.
const socket = new ElectrumWebSocket('hostNameOrIPNumber');

Alternatively, you can configure the socket behavior by providing one or more options:

// Optionally configure socket behavior with one or more of the ElectrumSocketOptions properties.
const options =
{
	enforceConsistentBrowserBehavior: false,
}

// Create the web socket with customized behavior.
const socket = new ElectrumWebSocket('hostNameOrIPNumber', options);

Connecting to the host

After you have created an ElectrumWebSocket, you can connect with the host:

await socket.connect();

Disconnecting from a host

When you no longer need the ElectrumWebSocket, you can disconnect from the host:

await socket.disconnect();

Sending messages

While connected, you can send messages with:

await socket.write('YourTextMessageHere');

Receiving messages

To receive messages from the socket, listen to the data emitted events.

// Set up handler for incoming data.
const onSocketData = async function(data: string)
{
	console.log(data);
}

// Register handler for incoming data.
socket.addEventListener('data', onSocketData);

Managing connection

The socket also emits connected and disconnected event over its lifetime:

// Signal indicating that the socket has connected.
socket.addEventListener('connected', onSocketConnected);

// Signal indicating that the socket has disconnected.
socket.addEventListener('disconnected', onSocketDisconnected);

Handling errors

When connecting the socket, you might get a promise rejection containing an error:

try
{
	await socket.connect();
}
catch (error)
{
	// Internal errors are bugs in the implementation, simply log and move on.
	if(error instanceof SocketInternalError)
	{
		console.error(error);
	}

	// Timeout during connection could be network or host problems, try again later?
	if(error instanceof SocketTimeoutError)
	{
		// Code to try again later
	}

	// Connection errors range from being something you can handle, to things outside of your control.
	if(error instanceof SocketConnectionError)
	{
		// Inspect error.message for more details, or just log, like this:
		console.error(error);
	}
}

When writing to the socket, you might get a promise rejection containing an error:

try
{
	await socket.write('message');
}
catch (error)
{
	// Internal errors are bugs in the implementation, simply log and move on.
	if(error instanceof SocketInternalError)
	{
		console.error(error);
	}

	// Write errors means the data was not sent, so maybe try again later?
	if(error instanceof SocketWriteError)
	{
		// Code to try again later
	}
}

Change Log

v4.0

Safety

• The following calls are now idempotent: connect(), disconnect(), write().
• The following calls now return a promise that resolves or reject when the action is completed: connect(), disconnect().
• The following calls are now safe to use concurrently: connect(), disconnect(), write().
• There is now four new custom errors: SocketInternalError, SocketTimeoutError, SocketConnectionError and SocketWriteError
• Event listeners are now assigned in only one place, and ensured not to create duplicates.
• Added edge-case and error handling tests.
• Added @throws to all calls that can throw.

Features

• There is now four new utility functions to return current state: isConnecting(), isConnected(), isDisconnecting and isDisconnected.
• Self-signed certificates are now allowed when enforceBrowserConsistency is set to false, and running in a non-browser environment.

Cleanups

• removed error events as these are now handled with promise rejections.
• removed support for sending Uint8Arrays, as the electrum protocol only sends strings.

v1.2

• Handle browser visibilty and connectivity events consistently.
• Added basic happy-path tests.

v1.1

• Changed library bundler to tsdown

v1.0

• Initial release