Electron CGI

Electron CGI is a library that enables creating requests in NodeJs that are then served by .NET.

The npm package is called electron-cgi.

The nuget package is called ElectronCgi.DotNet.

Here's an example of how you can interact with a .Net application from Node:

In NodeJs/Electron:

const { ConnectionBuilder } = require('electron-cgi');

const connection = new ConnectionBuilder()
        .connectTo('dotnet', 'run', '--project', 'DotNetConsoleProjectWithElectronCgiDotNetNugetPackage')
        .build();

connection.onDisconnect = () => {
    console.log('Lost connection to the .Net process');
};

connection.send('greeting', 'John', (err, theGreeting) => {
    if (err) {
        console.log(err);
        return;
    }
    console.log(theGreeting); // will print "Hello John!"
});

//or using promises

const theGreeting = await connection.send('greeting', 'John')

connection.close();

And in the .Net Console Application:

using ElectronCgi.DotNet;

//...
static void Main(string[] args)
{
    var connection = new ConnectionBuilder()
                        .WithLogging()
                        .Build();

    // expects a request named "greeting" with a string argument and returns a string
    connection.On<string, string>("greeting", name =>
    {
        return $"Hello {name}!";
    });

    // wait for incoming requests
    connection.Listen();        
}

How does it work?

Electron CGI establishes a "connection" with an external process. That external process must be configured to accept that connection. In the example above that's what the Listen method does.

In Node we can "send" requests (for example "greeting" with "John" as a parameter) and receive a response from the other process.

The way this communication channel is established is by using the connected process' stdin and stdout streams. This approach does not rely on staring up a web server and because of that introduces very little overhead in terms of the requests' round-trip time.

Changelog

Update version 1.0.3

Bugfix for Connection.Send(requestType, arg, responseArg => {...}) where argument type information for the response argument type was being inadvertently discarded.

Update version 1.0.2

Added the the UsingEncoding(System.Text.Encoding encoding) method to ConnectionBuilder, usage:

var connection = new ConnectionBuilder().UsingEncoding(System.Text.Encoding.UTF8).Build()

If you are having encoding issues with messages between Node and .NET failing because of special characters (e.g. ä,ö,ü) try to set the encoding this way in .NET.

Update version 1.0.1

• Error propagation to Node.js

  • An exception in a handler will be serialized and sent to Node.js (requires electron-cgi 1.0.0) and won't crash the process

• Bugfixes

Update version 1.0.0

• This version was uploaded incorrectly. Skip it.

Update version 0.0.5

• Duplex: ability to send requests from both .Net and Node.js

Update version 0.0.2

• Ability to serve request concurrently (uses System.Threading.Tasks.DataFlow)

Next steps

• Add the ability to send requests form .Net to Node
• Instead of making the process fail when there's an exception in a handler, serialise the exception and "surface" it in Node

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