chrome.runtime.connectNative from external url

I have a Google Chrome extension which contains the following two files...

manifest.json

{
    "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": "index.html"
        }
    },
    "icons": {
        "128": "icon-128.png"
    },
    "permissions": [
        "nativeMessaging"
    ],
    "externally_connectable": {
        "matches": ["*://*.chrome-extension.com/*"]
    },
    "background": {
        "scripts": ["background.js"]
    }
}

background.js

var sendResponseCallBack;

chrome.runtime.onMessageExternal.addListener(
    function(request, sender, sendResponse) {
        sendResponseCallBack = sendResponse;
        var message = {"comment": '*** ' + request['comment'] + ' ***'};
        var useNative = false;
        if (useNative) {
            connect();
            sendNativeMessage(message);
        }
        else {
            sendResponseCallBack(message);
        }
    }
);
function connect() {
    var hostName = "com.google.chrome.example.echo";
    port = chrome.runtime.connectNative(hostName);
    port.onMessage.addListener(onNativeMessage);
    port.onDisconnect.addListener(onDisconnected);
}
function sendNativeMessage(message) {
    port.postMessage(message);
}
function onNativeMessage(message) {
    port.disconnect();
    sendResponseCallBack(message);
}

I also configured the virtual host: chrome-extension.com to access to the url from a local server:

http://www.chrome-extension.com/

With the Chrome extension installed and enabled, if I access to:

http://www.chrome-extension.com/

and the variable useNative = false then I get a response from the plugin through: sendResponseCallBack(message);, but if useNative = true then I don't get any response from the plugin, I get: undefined and also the native operation which should take about 5 seconds, doesn't go thru because the undefined response is returned in 0 seconds.

I also have enabled another html page I access thru the extension url:

chrome-extension://knldjmfmopnpolahpmmgbagdohdnhkik/calc-with-os.html

Inside that page I include the calc-with-os.js file which contains the above functions: connect() sendNativeMessage(message) onNativeMessage(message) and the function: chrome.runtime.connectNative works properly performing the native process in all its phases.

Any idea on how can I connect to a native process from an external url?

[EDIT: TRY NUMBER 2]

Based on the comment of: @wOxxOm I did the following modification to the code with the purpose of don't send the message to fast and wait for the native process to start, but it is not still working.

Any other suggestions?

var port = null;
var sendResponseCallBack;

chrome.runtime.onMessageExternal.addListener(
    function(request, sender, sendResponse) {
        sendResponseCallBack = sendResponse;
        connect(request);
    }
);
function connect(request) {
    chrome.runtime.onConnect.addListener(function(p){
        port = p;
        port.onMessage.addListener(onNativeMessage);
        port.onDisconnect.addListener(onDisconnected);
        var message = {"comment": '*** ' + request['comment'] + ' ***'};
        sendNativeMessage(message);
    });
    var hostName = "com.google.chrome.example.echo";
    chrome.runtime.connectNative(hostName);
}
function sendNativeMessage(message) {
    port.postMessage(message);
}
function onNativeMessage(message) {
    port.disconnect();
    sendResponseCallBack(message);
}