chrome-native-messaging

Transform streams for writing Chrome App native messaging1 hosts in Node.js.

Install

npm i -S chrome-native-messaging

API

The module exports Input, Output, and Transform transform streams.
Input streams transform bytes to objects.
Output streams transform objects to bytes.
Use Transform to easily create custom object-to-object transform streams.

var nativeMessage = require('chrome-native-messaging');

process.stdin
    .pipe(new nativeMessage.Input())
    .pipe(new nativeMessage.Transform(function(msg, push, done) {
        var reply = getReplyFor(msg); // Implemented elsewhere by you.
        push(reply);                  // Push as many replies as you like.
        done();                       // Call when done pushing replies.
    }))
    .pipe(new nativeMessage.Output())
    .pipe(process.stdout)
;

Example

The app directory contains a sample Chrome App.
The host directory contains a native messaging host that you can send "readdir" messages to.
Go to the Chrome Extensions page (chrome://extensions/) and hit "Load unpacked extension...". Select the app directory. Look at the ID it received and put it in the host manifest.
The host directory contains the manifest that must be copied to the correct directory on OS X.
Install the host manifest:

sudo host/register.sh

On Windows (Run as Administrator):

host\register.bat

Open a new tab and hit Apps in the upper left. Launch the example app and send yourself messages.

Testing

Run npm test for the unit tests.
json2msg.js is a script that can convert lines of JSON into native messages. Use it to send messages to your host to see how it responds.
Pipe the output of your host to msg2json.js to see what its output looks like.

./json2msg.js < test.json | ./host/my_host.js | ./msg2json.js

On Windows:

node json2msg.js < test.json | node host\my_host.js | node msg2json.js

Logging

Enabling logging in Chrome can help find problems finding the manifest.
Quit Chrome first.

open -a Google\ Chrome --args --enable-logging --v=1

On Windows:

start chrome --enable-logging --v=1

View the log like this:

less ~/Library/Application\ Support/Google/Chrome/chrome_debug.log

On Windows:

type "C:\Users\%USERNAME%\AppData\Local\Google\Chrome\User Data\chrome_debug.log"

More info: http://www.chromium.org/for-testers/enable-logging