Wormhole

This module can be used to provide handy functionality on top of remote connections such as Inter-Process Communication (IPC). It's designed to be small and easy to use.

It has the following features:

• Send and receive events with arbitrary arguments
• RPC-style remote command calling
• Can be used on both sides of a communication channel

Wormhole is developed with process and ChildProcess (over IPC) in mind.

Installing

npm i @art-of-coding/wormhole

Example

This is an attempt to write a complete example. In this example we fork a process and then we want to communicate with it. By using wormhole on both ends, we can send and receive events and commands in both directions.

The master process:

import { fork } from 'child_process'
import Wormhole from '@art-of-coding/wormhole'

const child = fork('./example-child.js')
const wormhole = new Wormhole(child)

// Register a `startup` event handler
wormhole.events.on('startup', () => {
  console.log('received startup event!')
})

// Register an `add` command
wormhole.define('add', function (a: number, b: number) {
  return a + b
})

// Send the `quit` event to the child
setTimeout(() => wormhole.event('quit'), 5000)

The child process:

import Wormhole from '@art-of-coding/wormhole'

const wormhole = new Wormhole(process)

// Register a `quit` event handler
wormhole.events.once('quit', () => {
  process.exit(-1)
})

// Send an event
wormhole.event('startup')

// Call a remote command
wormhole.command<number>('add', 5, 6).then(result => {
  console.log(`5 + 6 = ${result}`)
})

API

new Wormhole (channel)

Instantiates a new wormhole instance.

• channel: The channel to use (must either be process or an instance of ChildProcess)

Events

A Wormhole instance is an EventEmitter with the following events:

• error: There was an error
• message: A received message that isn't handled by Wormhole
• disconnect: The channel is disconnected

wormhole.connected

Returns true if the channel is connected.

wormhole.pendingCallbacks

Returns the amount of pending command callbacks.

wormhole.events

Getter to get the events EventEmitter.

wormhole.events.on('some-event', () => {
  console.log('some-event emitted')
})

wormhole.define (name, fn, context)

Define a command.

If the command is not a promise, the result will be cast into one. Throwing an Error (or subclassed) results in the rejection of the promise.

• name: The name for this command
• fn: The function for this command
• context: The command context (optional)

wormhole.define('add', function (a, b) {
  if (isNaN(a) || isNaN(b)) {
    throw new TypeError('arguments must be numbers')
  }

  return a + b
})

wormhole.event (event, ...args)

Emit an event named event.

• event: The name of the event
• ...args: The event arguments

wormhole.command<TResult> (name, ...args): Promise<TResult>

Call a remote command named name.

• name: The name of the command to call
• ...args: The command arguments

wormhole.command<number>('add', 5, 6).then(result => {
  console.log(`5 + 6 = ${result}`)
})

wormhole.write (message)

Writes a message over the channel.

• message: The message primitive or object

wormhole.disconnect ()

Disconnects the channel and releases all resources. After calling this, the instance is no longer usable.

License

Copyright 2017-2021 Art of Coding.

This software is licensed under the MIT License.