How to send / receive message between chrome extension native messaging and c# app

Question

i'm newbie with chrome extension so i need to developing chrome extension by using native messaging to communication message with c#.exe application

Now problem : i can connected between extension (chrome.runtime.connectNative(hostName)) with c# but i cannot send/receive message

here is my code

main.js

// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

var port = null;

var getKeys = function(obj){
   var keys = [];
   for(var key in obj){
      keys.push(key);
   }
   return keys;
}


function appendMessage(text) {
  document.getElementById('response').innerHTML += "<p>" + text + "</p>";
}

function updateUiState() {
  if (port) {
    document.getElementById('connect-button').style.display = 'none';
    document.getElementById('input-text').style.display = 'block';
    document.getElementById('send-message-button').style.display = 'block';
  } else {
    document.getElementById('connect-button').style.display = 'block';
    document.getElementById('input-text').style.display = 'none';
    document.getElementById('send-message-button').style.display = 'none';
  }
}

function sendNativeMessage() {
  message = {"text": document.getElementById('input-text').value};
  port.postMessage(message);
  appendMessage("Sent message: <b>" + JSON.stringify(message) + "</b>");
}

function onNativeMessage(message) {
  appendMessage("Received message: <b>" + JSON.stringify(message) + "</b>");
}

function onDisconnected() {
  appendMessage("Failed to connect: " + chrome.runtime.lastError.message);
  port = null;
  updateUiState();
}

function connect() {
  var hostName = "com.google.chrome.example.echo";
  appendMessage("Connecting to native messaging host <b>" + hostName + "</b>")
  port = chrome.runtime.connectNative(hostName);
  port.onMessage.addListener(onNativeMessage);
  port.onDisconnect.addListener(onDisconnected);
  updateUiState();
}

document.addEventListener('DOMContentLoaded', function () {
  document.getElementById('connect-button').addEventListener(
      'click', connect);
  document.getElementById('send-message-button').addEventListener(
      'click', sendNativeMessage);
  updateUiState();
});

app.exe - C#

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace sign
{
    class Program
    {
        public static void Main(string[] args)
        {
            JObject data;
            while ((data = Read()) != null)
            {
                var processed = ProcessMessage(data);
                Write(processed);
                if (processed == "exit")
                {
                    return;
                }
            }
        }

        public static string ProcessMessage(JObject data)
        {
            var message = data["message"].Value<string>();
            switch (message)
            {
                case "test":
                    return "testing!";
                case "exit":
                    return "exit";
                default:
                    return "echo: " + message;
            }
        }

        public static JObject Read()
        {
            var stdin = Console.OpenStandardInput();
            var length = 0;

            var lengthBytes = new byte[4];
            stdin.Read(lengthBytes, 0, 4);
            length = BitConverter.ToInt32(lengthBytes, 0);

            var buffer = new char[length];
            using (var reader = new StreamReader(stdin))
            {
                while (reader.Peek() >= 0)
                {
                    reader.Read(buffer, 0, buffer.Length);
                }
            }

            return (JObject)JsonConvert.DeserializeObject<JObject>(new string(buffer))["data"];
        }

        public static void Write(JToken data)
        {
            var json = new JObject();
            json["data"] = data;

            var bytes = System.Text.Encoding.UTF8.GetBytes(json.ToString(Formatting.None));

            var stdout = Console.OpenStandardOutput();
            stdout.WriteByte((byte)((bytes.Length >> 0) & 0xFF));
            stdout.WriteByte((byte)((bytes.Length >> 8) & 0xFF));
            stdout.WriteByte((byte)((bytes.Length >> 16) & 0xFF));
            stdout.WriteByte((byte)((bytes.Length >> 24) & 0xFF));
            stdout.Write(bytes, 0, bytes.Length);
            stdout.Flush();
        }
    }
}

.json

// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

{
  "name": "com.google.chrome.example.echo",
  "description": "Chrome Native Messaging API Example Host",
  "path": "native-messaging-example-host.bat",
  "type": "stdio",
  "allowed_origins": [
    "chrome-extension://knldjmfmopnpolahpmmgbagdohdnhkik/"
  ]
}

.bat

@echo off

start %~dp0/Debug/sign.exe

.manifest.json

{
  // Extension ID: knldjmfmopnpolahpmmgbagdohdnhkik
  "key": "MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDcBHwzDvyBQ6bDppkIs9MP4ksKqCMyXQ/A52JivHZKh4YO/9vJsT3oaYhSpDCE9RPocOEQvwsHsFReW2nUEc6OLLyoCFFxIb7KkLGsmfakkut/fFdNJYh0xOTbSN8YvLWcqph09XAY2Y/f0AL7vfO1cuCqtkMt8hFrBGWxDdf9CQIDAQAB",
  "name": "Native Messaging Example",
  "version": "1.0",
  "manifest_version": 2,
  "description": "Send a message to a native application.",
  "app": {
    "launch": {
      "local_path": "main.html"
    }
  },
  "icons": {
    "128": "icon-128.png"
  },
  "permissions": [
    "nativeMessaging"
  ]
}

please advice me some tips.. thank you very much

Answer 1

this is the correct .json

{
  "name": "com.google.chrome.example.echo",
  "description": "Chrome Native Messaging API Example Host",
  "path": "native-messaging-example-host.bat",
  "type": "stdio",
  "allowed_origins": [
    "chrome-extension://knldjmfmopnpolahpmmgbagdohdnhkik/"
  ],
  "permissions": [
    "nativeMessaging"
  ]
}

Answer 2

You can not use stdout because it is a subprocess of Chrome.exe. File write is possible. Do it.