simple-nativemessage

this is a nodejs script, to be used for communicating between a browser extensions and a native message host

it is available from npm at npm : simple-nativemessage

v1.0 - a simple copy and paste solution, designed to be as simple as possible to highlight the concepts

v2.0 - used with npm i simple-nativemessage

      var nmhost    = require('simple-nativemessage');
      var debug     = nmhost.debug;
      
      nmhost.rec    = rec;
      
      
      function rec(json){
      
            debug('rec',JSON.stringify(json,null,4));

                                    
            switch(json.type){
            
              case 'hello'      : nmhost.send('world');       break;
              
            }//switch

      }//rec

example chrome extension

see the example directory for working example

install

the extension is currently built for chrome based browsers on windows

1. download

download the repository to a convenient location - https://github.com/javascript-2020/simple-nativemessage

2. install extension

open chrome://extensions

in the top right, switch to developer mode

click load unpacked

navigate to example/ext and select folder

3. setup extension

find the extension named simple-nativemessage example extension

copy the extension id

paste the extension id into allow_origins value in example/ext/nmhost/nmhost-manifest.json

if using externally connectable ( see below ) paste the extension id into example/webpage/index.html

4. setup native messaging

run example/ext/nmhost/install-nmhost.bat as administrator ( right-click 'Run as administrator' )

this will create a registry key for the native messaging host, under

HKLM\Software\Google\Chrome\NativeMessagingHosts\

specifying the location of example/ext/nmhost/nmhost-manifest.json

5. optional, extension connection from a webpage

to use the externally connectable extension interface, which allows a webpage to communicate directly with an extension, the webpage must be served from at least a second level domain, for local servers this means creating a dns record -- ie editing the hosts file

https://developer.chrome.com/docs/extensions/mv3/manifest/externally_connectable/

the extension is designed to be externally connectable from

http://site.localhost/*

so the host file will need the entry

127.0.0.1 site.localhost

c:/Windows/System32/drivers/etc/hosts

/etc/hosts

communication with the extension/native message host can always be achieved using the content script example/ext/content-script/content-script.js

6. start server

open a cmd prompt navigate to example/webpage , run the server :

node server.js

7. test native message

open chrome based browser at http://localhost:8081

or if using externally connectable http://site.localhost:8081

content-script.js

should be displayed, meaning the content script has been added to the page

clicking the test button under the content script, should print hello

then returning from the native message host, should print world

native messaging is working

calculator launches the calculator app that comes with all versions of window

elevated launches the calculator with elevated permissions

launching applications like these is a common use for native messaging

uninstall

1. remove extension

open chrome://extensions

find the extension named simple-nativemessage example extension

click remove

2. remove native messaging

run example/ext/nmhost/uninstall-nmhost.bat as administrator ( right click 'Run as administrator' )

this will remove the previously created registry key