electron-common-ipc

An IPC (Inter-Process Communication) bus for applications built for Node.js and/or Electron.js.

This bus offers an EventEmitter-like API for exchanging data between any processes (Node process/s, Electron Main and Electron Renderer process/s).

• Node to Node,
• Node to Electron (Master and Renderer processes + Frames),
• Electron to Node,
• Electron to Electron.

You can exchange a lot of different kinds of data and even transfer MessagePort/s between 2 renderers.

For Node processes support, you need to instanciate a "BusBroker" (Net socket server) in charge to commute messages to right listeners.
For Electron Main/Renderer processes, you need an additional broker : "BusBridge" in charge to commute messages between renderers WebPage and WebFrame, Master and Node.

You can have a pure Node bus, just using BusBroker (even working out of Electron) You can have a Electron Main/Renderer processes bus, just using BusBridge You can have a dual-mode supporting all kind of processes by creating BusBroker/BusBridge.

A WebPage is then able to dialog with a node process and vice-versa.

Features

• EventEmitter oriented API
• Transfer MessagePort/s
• Works with Electron sandboxed renderer process
• Support for Electron renderer affinity (several webpages hosted in the same renderer process)
• Basic remote API calls/events and pending messages management with Services
• ContextIsolation not yet supported, in progress
• Support broadcast and peer2peer message

Installation

npm install electron-common-ipc

Dependencies

• https://github.com/emmkimme/socket-serializer
• https://github.com/emmkimme/json-helpers
• http://electron.atom.io/
• http://nodejs.org/

Technical Overview

Objective

Usage

Scenarii

Electron App

Pseuso code in...
Main Process

const ipcBusBridge = IpcBusBridge.Create();
ipcBusBridge.connect().then(() => 
    const ipcBusClientElectronMain = IpcBusClient.Create();
    ipcBusClientElectronMain.connect();
});

Renderer Process (nodeIntegration = true) (WebFrame supported)

const ipcBusClientRenderer1 = IpcBusClient.Create();
ipcBusClientRenderer1.connect();

Sandboxed Renderer Process (sandbox = true) (WebFrame supported)

• load ipcbus library in the preload file

const ipcBusClientRenderer2 = IpcBusClient.Create();
ipcBusClientRenderer2.connect();

done
ipcBusClientElectronMain, ipcBusClientRenderer1 and ipcBusClientRenderer2 can exchange data.

NodeJS App

Pseuso code in...
Main Process

• find a free port (using Socket port helpers for instance)

const ipcBusBroker = IpcBusBroker.Create();
ipcBusBroker.connect([free port]).then(() => {
    const ipcBusClientNodeMain = IpcBusClient.Create();
    ipcBusClientNodeMain.connect([free port]);
});

Child node process

• retrieve free port through commandline or environment variable

const ipcBusClientNodeChild = IpcBusClient.Create()
ipcBusClientNodeChild.connect([free port]);

done
ipcBusClientNodeMain and ipcBusClientNodeChild can exchange data.

Hybrid App (NodeJS and Electron)

Pseuso code in...
Main Process

ipBusBridge.connect([same port as the ipcBusBroker]);

done
ipcBusClientElectronMain, ipcBusClientRenderer1 and ipcBusClientRenderer2, ipcBusClientNodeMain and ipcBusClientNodeChild can exchange data.

Initialization

If you are using the bus in a renderer process (page), you must take care of the context :

• sandbox
• nodeIntegration
• cross-frames

In order to have bus working in all contexts you can register the bus in the preload file of your BrowserWindow

const win = new BrowserWindow({
    webPreferences: {
        sandbox: true/false (both supported)
        preload: 'preload-ipc.bundle.js',
        contextIsolation: false
    }
});

To be supported in Frames

const win = new BrowserWindow({
    webPreferences: {
        sandbox: true/false (both supported)
        nodeIntegrationInSubFrames: true,
        preload: 'preload-ipc.bundle.js'
    }
});

preload-ipc.js

const electronCommonIPC = require('electron-common-ipc/lib/electron-common-ipc-preload');
electronCommonIPC.PreloadElectronCommonIPC();

You have to bundle your file :

browserify -o ./preload-ipc.bundle.js -x electron ./preload-ipc.js

Use Browserify >= 16.5.0 for having full support of EventEmitter.

Sample

// Load modules
const ipcBusModule = require("electron-ipc-bus");
const electronApp = require('electron').app;

// Configuration
const ipcBusPath = 50494;
// const ipcBusPath = '/myfavorite/path';

// Startup
electronApp.on('ready', function () {
    // Create broker if you want to interact with NodeJS process
    const ipcBusBroker = ipcBusModule.IpcBusBroker.Create();
    // Start broker
    ipcBusBroker.connect(ipcBusPath)
        .then((msg) => {
            console.log('IpcBusBroker started');

            // Create bridge
            const ipcBusBridge = ipcBusModule.IpcBusBridge.Create();
            // Connect using a busPath if you want to interact with NodeJS process
            ipcBusBridge.connect(ipcBusPath)
                .then((msg) => {
                    console.log('IpcBusBridge started');

                    // Create clients
                    const ipcBusClient1 = ipcBusModule.IpcBusClient.Create();
                    const ipcBusClient2 = ipcBusModule.IpcBusClient.Create();
                    Promise.all([ipcBusClient1.connect({ peerName: 'client1' }), ipcBusClient2.connect({ peerName: 'client2' })])
                        .then((msg) => {
                            // Chatting on channel 'greeting'
                            ipcBusClient1.addListener('greeting', (ipcBusEvent, greetingMsg) => {
                                // This is a request, we have to reply immediatly using request.resolve or request.reject
                                if (ipcBusEvent.request) {
                                    ipcBusEvent.request.resolve(`thanks to you, dear #${ipcBusEvent.sender.name}`);
                                }
                                // Else we reply using a contractual channel
                                else {
                                    ipcBusClient1.send('greeting-reply', `${ipcBusClient1.peer.name}: thanks to all listeners`)
                                }
                                console.log(ipcBusClient1.peer.name + ' received ' + ipcBusEvent.channel + ': ' + greetingMsg);
                            });

                            ipcBusClient2.addListener('greeting', (ipcBusEvent, greetingMsg) => {
                                if (ipcBusEvent.request) {
                                    ipcBusEvent.request.resolve(`thanks to you, dear #${ipcBusEvent.sender.name}`);
                                }
                                else {
                                    ipcBusClient2.send('greeting-reply', `${ipcBusClient2.peer.name}: thanks to all listeners`)
                                }
                                console.log(ipcBusClient2.peer.name + ' received ' + ipcBusEvent.channel + ': ' + greetingMsg);
                            });

                            ipcBusClient1.addListener('greeting-reply', (ipcBusEvent, greetingReplyMsg) => {
                                console.log(greetingReplyMsg);
                                console.log(ipcBusClient1.peer.name + ' received ' + ipcBusEvent.channel + ': ' + greetingReplyMsg);
                            });

                            ipcBusClient2.send('greeting', 'hello everyone!');

                            // This call will fail, too short to answer on time !
                            ipcBusClient2.request('greeting', 0, 'hello partner, please answer immediatly')
                                .then((ipcBusRequestResponse) => {
                                    console.log(JSON.stringify(ipcBusRequestResponse.event.sender.name) + ' replied ' + ipcBusRequestResponse.payload);
                                })
                                .catch((err) => {
                                    console.log('Too late, I have no friend :-(');
                                });

                            ipcBusClient1.request('greeting', 1000, 'hello partner, please answer within 1sec!')
                                .then((ipcBusRequestResponse) => {
                                    console.log(JSON.stringify(ipcBusRequestResponse.event.sender.name) + ' replied within 1sec1 ' + ipcBusRequestResponse.payload);
                                })
                                .catch((err) => {
                                    console.log('I have no friend :-(');
                                });
                        });
                });
        });
});

Common options

Some interfaces are sharing the same kind of options.
In order to be consistent in term of behavior and naming we have common interfaces for options.

export interface IpcTimeoutOptions {
    timeoutDelay?: number;
}

• timeoutDelay = number (milliseconds)

• timeoutDelay [0 | undefined | null] : use a default timeout of 2000ms

• timeoutDelay < 0 : an infinite waiting

• timeoutDelay > 0 : wait for the expected time

A timeoutdelay below zero leads to an infinite waiting and may lead to memory leak as internals will not be freed if there is an issue.

export interface IpcSocketBufferingOptions {
    socketBuffer?: number;
} 

• socketBuffer [0 | undefined | null] : message is serialized in small pieces written immediatly to the socket
• socketBuffer < 0 : message is serialized in objects (number, string, buffer...), each object is written immediatly to the socket
• socketBuffer > 0 : message is serialized in objects, objects are written only in one shot when reaching a size of socketBuffer in bytes.

export interface IpcNetOptions {
    port?: number;
    host?: string;
    path?: string;
    useBridge?: boolean;
}

See NodeJS Net

• useBridge : the client will use the BusBrige to discuss with the socket server (BusBroker). It is more efficient to go to the bridge than connecting directly to the net server (BusBroker).

IpcBusBroker

Dispatching of Node messages is managed by a broker. You can have only one single Broker for the whole application.
The broker can be instanciated in a node process or in the master process (not in renderer processes).
For performance purpose, it is better to instanciate the broker in an independent node process.

Interface

interface IpcBusBroker {
    connect(options?: IpcBusBroker.StartOptions): Promise<string>;
    close(): void;
    queryState(): Object;
    isServiceAvailable(serviceName: string): boolean;
}

Initialization of the Broker (in a node process)

const ipcBusModule = require("electron-common-ipc");
const ipcBusBroker = ipcBusModule.IpcBusBroker.Create([busPath]);

The require() call loads the module and IpcBusBroker.Create setups the broker with the busPath.

// Socket path
const ipcBusBroker = ipcBusModule.IpcBusBroker.Create();

Methods

connect(options?: IpcBusBroker.StartOptions) : Promise < string >

// Socket path
ipcBusBroker.connect('/my-ipc-bus-path') 
    .then(() => console.log('success'))
    .catch((err) => console.log(err))

// Port number
ipcBusBroker.connect(58666) 
    .then(() => console.log('success'))
    .catch((err) => console.log(err))

Starts the broker dispatcher. If failed (timeout or any other internal error), err contains the error message.

close()

ipcBusBroker.close() 

queryState() - for debugging purpose only

var queryState = ipcBusBroker.queryState() 

Returns the list of pair <channel, peer> subscriptions. Format may change from one version to another. This information can be retrieved from an IpcBusClient through the channel : /electron-common-ipc/queryState

isServiceAvailable(serviceName): boolean

• serviceName: string

ipcBusBroker.isServiceAvailable('mySettings') 

Test if a service is started. This information can be retrieved from an IpcBusClient through the channel : /electron-common-ipc/serviceAvailable

IpcBusBridge

Dispatching of Renderer messages is managed by a bridge. You can have only one single bridge for the whole application. The bridge must be instanciated in the master process only. Without this bridge, Renderer and Node processes are not able to dialog.

Interface

interface IpcBusBridge {
    connect(options?: IpcBusBridge.StartOptions): Promise<string>;
    close(): void;
}

Initialization of the Bridge (in the master process)

const ipcBusModule = require("electron-common-ipc");
const ipcBusBridge = ipcBusModule.IpcBusBridge.Create();

Methods

connect(options?: IpcBusBridge.StartOptions) : Promise < string >

// Socket path
ipcBusBridge.connect('/my-ipc-bus-path') 
    .then(() => console.log('success'))
    .catch((err) => console.log(err))

// Port number
ipcBusBridge.connect(58666) 
    .then(() => console.log('success'))
    .catch((err) => console.log(err))

Starts the bridge dispatcher. If failed (timeout or any other internal error), err contains the error message.

close()

ipcBusBridge.stop() 

IpcBusClient

The IpcBusClient is an instance of the EventEmitter class.

When you register a callback to a specified channel. Each time a message is received on this channel, the callback is called. The callback must follow the IpcBusListener signature (see below).

Interface

interface IpcBusClient extends events.EventEmitter {
    readonly peerName: string;

    connect(options?: IpcBusClient.ConnectOptions): Promise<string>;
    close(): void;

    send(channel: string, ...args: any[]): void;
    request(channel: string, timeoutDelay: number, ...args: any[]): Promise<IpcBusRequestResponse>;

    // EventEmitter overriden API
    addListener(channel: string, listener: IpcBusListener): this;
    removeListener(channel: string, listener: IpcBusListener): this;
    on(channel: string, listener: IpcBusListener): this;
    once(channel: string, listener: IpcBusListener): this;
    off(channel: string, listener: IpcBusListener): this;

    // Added in Node 6...
    prependListener(channel: string, listener: IpcBusListener): this;
    prependOnceListener(channel: string, listener: IpcBusListener): this;
}

Initialization in the Main/Browser Node process

const ipcBusModule = require("electron-common-ipc");
const ipcBus = ipcBusModule.IpcBusClient.Create();

ipcBus.connect([net options]);

IpcBusClient.connect setups the client with the busPath that was used to connect the broker.

Initialization in a Node single process

ipcBus.connect('/my-ipc-bus-path');

Initialization in a Renderer process (either sandboxed or not)

if use sandbox you have to preload code like this:

const electronCommonIPC = require('electron-common-ipc');
if (electronCommonIPC.PreloadElectronCommonIPC()) {
  electronCommonIPC.ActivateIpcBusTrace(true);
  window.ipcBus = window.ElectronCommonIPC.CreateIpcBusClient();
}

if not, just type this code in your renderer process:

if (electronCommonIPC.PreloadElectronCommonIPC()) {
    electronCommonIPC.ActivateIpcBusTrace(true);
    const ipcBus = window.ElectronCommonIPC.CreateIpcBusClient();
}

NOTE: There is no notion of port, buspath in a renderer. IpcBusRenderer connects automatically to the instance of the bridge.

Property

peer

For debugging purpose, each IpcBusClient is identified by a peer.

type IpcBusProcessType = 'main' | 'renderer' | 'renderer-frame' | 'node';

interface IpcBusProcess {
    type: IpcBusProcessType;
    pid: number;
    rid?: number;
    wcid?: number;
}

interface IpcBusPeer {
    id: number;
    name: string;
    process: IpcBusProcess;
}

IpcBusPeer contains :

• an uniq read-only id
• the name of the peer, this name can be changed during the connection (IpcBusClient.connect)
• the process context of the peer.

IpcBusProcess contains :

• type : type of the context : 'main' | 'renderer' | 'renderer-frame' | 'node'
• pid : id of the process which hosts the the peer
• rid : client id of the renderer process where the peer is hosted (equivalent to the value of --renderer-client-id option in the commandline of the renderer process), only valid for a 'renderer' process
• wcid : webContents id of the peer, only valid for a 'renderer' process

For a 'renderer' process the pid depends on the version of Electron.

Electron < 1.7.1 : pid = wcid

Connectivity Methods

connect(options?: IpcBusClient.ConnectOptions) : Promise < string >

Basic usage

ipcBus.connect().then((eventName) => console.log("Connected to Ipc bus !"))

Provide a timeout

ipcBus.connect({ timeoutDelay: 2000 }).then((eventName) => console.log("Connected to Ipc bus !"))

Provide a peer name

ipcBus.connect({ peerName: 'client2' }).then((eventName) => console.log("Connected to Ipc bus !"))

Provide all options

ipcBus.connect({ peerName: 'client2', timeoutDelay: 2000 }).then((eventName) => console.log("Connected to Ipc bus !"))

For a bus in a renderer, it fails if the Bridge is not started else it fails if the Broker is not started. Most of the functions below will fail if the connection is not established (you have to wait for the connect promise). A timeoutdelay below zero leads to an infinite waiting.

close()

ipcBus.close()

addListener(channel, listener)

• channel: string
• listener: IpcBusListener

Listens to channel, when a new message arrives listener would be called with listener(event, args...).

NOTE: on, prependListener, once and prependOnceListener methods are supported as well

removeListener(channel, listener)

• channel: string
• listener: IpcBusListener

Removes the specified listener from the listeners array for the specified channel.

NOTE: off method is supported as well

removeAllListeners([channel])

channel: String (optional)

Removes all listeners, or those of the specified channel.

IpcBusListener(event, ...args) callback

• event: IpcBusEvent
• ...args: any[]): void

The first parameter of the callback is always an event which contains the channel and the origin of the message (sender).

function HelloHandler(ipcBusEvent, content) {
    console.log("Received '" + content + "' on channel '" + ipcBusEvent.channel +"' from #" + ipcBusEvent.sender.peerName)
}
ipcBus.on("Hello!", HelloHandler)

Posting Methods

send(channel [, ...args])

• channel: string
• ...args: any[]

Sends a message asynchronously via channel, you can also send arbitrary arguments. Arguments will be serialized in JSON internally and hence no functions or prototype chain will be included.

ipcBus.send("Hello!", { name: "My age !"}, "is", 10)

request(channel: string, timeoutDelay: number, ...args: any[]): Promise

• channel: string
• timeoutDelay = timeoutDelay: number (milliseconds)
• ...args: any[]

Sends a request message on specified channel. The returned Promise is settled when a result is available. The parameter timeoutDelay defines how much time we're waiting for the response. A timeoutdelay below zero leads to an infinite waiting.

The Promise provides an IpcBusRequestResponse object:

interface IpcBusRequestResponse {
    event: IpcBusEvent;
    payload?: Object | string;
    err?: string;
}

ipcBus.request("compute", 0, "2*PI*9")
    .then(ipcBusRequestResponse) {
        console.log("channel = " + ipcBusRequestResponse.event.channel + ", response = " + ipcBusRequestResponse.payload + ", from = " + ipcBusRequestResponse.event.sender.peerName);
     }
     .catch(ipcBusRequestResponse) {
        console.log("err = " + ipcBusRequestResponse.err);
     }

With timeout

ipcBus.request("compute", 2000, "2*PI*9")
...

IpcBusEvent object

interface IpcBusEvent {
    channel: string;
    sender: IpcBusSender {
        peerName: string;
    };
    request?: IpcBusRequest {
        resolve(payload: Object | string): void;
        reject(err: string): void;
    };
}

The event object passed to the listener has the following properties:

event.channel: string

channel delivering the message

event.sender.peerName: string

peerName of the sender

event.request [optional]: IpcBusRequest

If present, the message is a request. Listener can resolve the request by calling event.request.resolve() with the response or can reject the request by calling event.request.reject() with an error message.

IpcBusService

The IpcBusService creates an IPC endpoint that can be requested via remote calls and send events.

Interface

interface IpcBusService {
    start(): void;
    stop(): void;
    registerCallHandler(name: string, handler: IpcBusServiceCallHandler): void;
    sendEvent(eventName: string, ...args: any[]): void;
}

IpcBusServiceCall

Message sent to a service to execute a remote call.

interface IpcBusServiceCall {
    handlerName: string;
    args: any[];
}

IpcBusServiceCallHandler

Prototype of a method that will be executed to handle a service's call.

interface IpcBusServiceCallHandler {
    (call: IpcBusServiceCall, request: IpcBusRequest): void;
}

Creation (without an outer implementation)

const ipcBusModule = require("electron-common-ipc");
...
// ipcBusClient is a connected instance of IpcBusClient
const ipcMyService = ipcBusModule.IpcBusService.Create(ipcBusClient, 'myService');

Creation (with an outer instance)

const ipcBusModule = require("electron-common-ipc");
...
const myOuterServiceInstance = {};
myOuterServiceInstance.test = () => { return 'This is a test'; };
...
// ipcBusClient is a connected instance of IpcBusClient
const ipcMyService = ipcBusModule.IpcBusService.Create(ipcBusClient, 'myService', myOuterServiceInstance);

NOTE : This constructor will automatically register all methods of myOuterServiceImpl as call handlers using registerCallHandler().

Methods

start(): void

This makes the service to listen and serve incoming remote calls. The service also sends the IPCBUS_SERVICE_EVENT_START event. NOTE : If an outerrouter service's instance has been specified at construction time, connect() will overload its This method will overload

stop(): void

This makes the service to stop listen and serve incoming remote calls. The service also sends the IPCBUS_SERVICE_EVENT_STOP event.

registerCallHandler(name, handler): void

• name: string
• handler: IpcBusServiceCallHandler This sets the function that will be executed to serve the specified remote call. As this is run in the context of a promise, the function must call either request.resolve() or request.reject() to fulfill the promise.

ipcMyService.registerCallHandler('getCurrentTime', (event, call) => {
    if (event.request) {
            try {                        {
                request.resolve(new Date().getTime());
            } catch(e) {
                request.reject(e);
            }
        });
    }

sendEvent(name, ...args): void

• name: string
• args: any[] This sends a service event message.

ipcMyService.sendEvent('timeChanged', new Date().getTime());

IpcBusServiceProxy

The IpcBusServiceProxy creates an IPC endpoint that can be used to execute calls on a service and listen its events.

Interface

interface IpcBusServiceProxy extends events.EventEmitter {
    readonly isStarted: boolean;

    getStatus(): Promise<ServiceStatus>;
    call<T>(handlerName: string, ...args: any[]): Promise<T>;
    getWrapper<T>(): T;

    connect<T>(timeoutDelay?: number): Promise<T>
    close(): Promise<void>;

IpcBusServiceEvent

Message sent to a service's proxy to trigger the code associated to this event.

interface IpcBusServiceEvent {
    eventName: string;
    args: any[];
}

IpcBusServiceEventHandler

Prototype of a method that will be executed to handle a service's call.

interface IpcBusServiceEventHandler {
    (event: IpcBusServiceEvent): void;
}

Creation

const ipcBusModule = require("electron-common-ipc");
...
// ipcBusClient is a connected instance of IpcBusClient
const ipcMyServiceProxy = ipcBusModule.IpcBusServiceProxy.Create(ipcBusClient, 'myService', 2000); // 2000 ms for call timeout (default is 1000 ms)

Properties

isAvailable: boolean

Availability of the associated service (available means that the service is started).

Methods

checkAvailability(): Promise< boolean >

This asynchronously requests the service availability to the Broker.

ipcMyServiceProxy.checkAvailability()
        .then(
            (availability) => console.log(`MyService availability = ${availability}`),
            (err) => console.log(`Failed to get MyService availability (${err})`));

call(handlerName: string, timeout: number, ...args: any[]): Promise< T >

• handlerName: string
• timeout: number
• args: any[] This sends a service event message.

ipcMyServiceProxy.call('getCurrentTime')
        .then(
            (currentTime) => console.log(`Current Time = ${currentTime}`),
            (err) => console.log(`Failed to get current time : ${err}`));

EventEmitter interface

This allow to handle events emitted by remote RPC service. Please refers to the EventEmitter class documentation for more information.

• addListener(event: string, listener: IpcBusServiceEventHandler): this;
• removeListener(event: string, listener: IpcBusServiceEventHandler): this;
• on(event: string, listener: IpcBusServiceEventHandler): this;
• once(event: string, listener: IpcBusServiceEventHandler): this;
• off(event: string, listener: IpcBusServiceEventHandler): this;
• removeAllListeners(event?: string): this;
• prependListener(event: string, listener: IpcBusServiceEventHandler): this;
• prependOnceListener(event: string, listener: IpcBusServiceEventHandler): this;

The wrapper implements EventEmitter as well. If the interface of the service emits an event it will be receiced by the wrapper of the proxy.

Test application

The test-app folder contains all sources of the testing application.

NOTE: This folder is not packaged by NPM.

To build the application:

cd examples
cd test-app
npm install
npm run build

To run the application:

npm run connect

To run the application in sandboxed mode:

npm run connect-sandboxed

Possible enhancements

• Support several brokers each with its own buspath in order to distribute the traffic load.
• Add an optional spy for debugging purpose

MIT License

Copyright (c) 2022 Emmanuel Kimmerlin

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.