Port error: Could not establish connection. Receiv

Question

I'm developing an extension in Chrome, and there's a problem. In my inject.js, I make a request like:

chrome.extension.sendRequest({command:'skip'},callback)

and in my `background.js I simply add a request Listener like:

chrome.extension.onrequest.addListener(function(req,sender,res){console.log("procession"})

But there's an error:

Port error: Could not establish connection. Receiving end does not exist

It seems a bug in chrome? PS:
part of my manifest.json

"background": {
    "scripts": ["background.js"]
  },
  "content_scripts": [
    {
      "matches": ["&lt all_urls &gt"], 
      "js": ["inject.js"]
    }
  ],

I'm in Chromium 17, and I tried reloading the extension, reopening the browser... nothing happened
some one get some ideas?

Answer 1

This isn't always the cause, but if you have an error in your background.js, you should check this link:

Inspect views: _generated_background_page.html

in the Extensions page, which will show you any JavaScript errors.

This was preventing my connections from getting established.

Answer 2

An HTML background page didn't work for me in Chrome 20.0.1132.57 m on Windows 7 with the same error:

Port error: Could not establish connection. Receiving end does not exist. miscellaneous_bindings:232

I tried using a background.js script with the following content:

chrome.extension.onConnect.addListener(function(port) {
    port.onMessage.addListener(function(msg) {
        // May be empty.
    });
});

That solved the immediate onDisconnect in my content script:

port = chrome.extension.connect();
port.onDisconnect.addListener(function (event) {
    // Happened immediately before adding the proper backend setup.
    // With proper backend setup, allows to determine the extension being disabled or unloaded.
});

The correct code came from Chromium Extensions messaging example: http://src.chromium.org/viewvc/chrome/trunk/src/chrome/common/extensions/docs/examples/api/messaging/timer/page.js?view=markup

The example also contains the second part that serves as a backend for sendRequest, but I haven't tested it myself:

chrome.extension.onRequest.addListener(
    function(request, sender, sendResponse) {
        // Don't know if it may be empty or a sendResponse call is required.
    });

Answer 3

I was seeing this problem, where my content script wasn't loading, so posting a message was never happening.

The problem turned out to be that I had the background script inspector open and was just pushing Cmd+R (refresh), but there was a bug in my manifest.json. When I actually went to the extensions page and reloaded that page, I got the alert showing the manifest error.

Basically, I saw this because my content scripts never loaded in the first place and I thought I was refreshing my manifest, but I wasn't.

Answer 4

Confronting with the same issue now.

//Here is my former background.js:

chrome.runtime.onInstalled.addListener(function () {
  //some other code here
  chrome.runtime.onMessage.addListener(function (message, sender, sendResponse) {
    if (message.url) {
        chrome.downloads.download({
            url: message.url,
            conflictAction: 'uniquify',
            saveAs: false
        });
    }
});});//(Sorry, I tried but failed to put the last bracket on next line)

You see, the chrome.runtime.onMessage.addListener is fired when the event onInstalled happpens, and when I get it out of this scope, and make my code like this:

chrome.runtime.onInstalled.addListener(function () {
  //some other code here
});  
chrome.runtime.onMessage.addListener(function (message, sender, sendResponse) {
    if (message.url) {
        chrome.downloads.download({
            url: message.url,
            conflictAction: 'uniquify',
            saveAs: false
        });
    }
});

It works well now. Hope to be helpful.

Answer 5

Check the latest manuals: http://developer.chrome.com/extensions/messaging.html

Note: If multiple pages are listening for onMessage events, only the first to call sendResponse() for a particular event will succeed in sending the response. All other responses to that event will be ignored.

Close your tabs, leave only one page, and check. In my case this was the issue.

Answer 6

I'm using sendMessage and onMessage for communication too, and in my workflow I first send a message from injected.js to my background.js and I also got "Port error: Could not establish connection. Receiving end does not exist." error.

So I decided to deal with using the responses functionalities ( like ACK ), and if background doesn't respond I keep trying with a setTimeout like so.

//background.js

...
chrome.extension.onMessage.addListener(function(request, sender, sendResponse) {
...
//some code

sendResponse({status: 'everything ok'})
return true;    
});

//injected.js

var myInjectedFunctionality = function() {

    chrome.extension.sendMessage({method: "Steroids:loadScripts"}, function(res) {
        if(res && res.status) {
            } else {
                setTimeout(myInjectedFunctionality, 3000);
            }
    });
};
myInjectedFunctionality();

My code is now running properly so I think that the explanation is easy to view. Chrome don't prepare Background.js and connection stuffs when it inject your code in the pages where you want to, and so makes nobody listen for your sent message, so if no one is listening, just keep trying like I do.