1chrome.extension.onConnect.addListener(function(port) {
2  port.onMessage.addListener(function(msg) {
3    port.postMessage({counter: msg.counter+1});
4  });
5});
6
7chrome.extension.onRequest.addListener(
8  function(request, sender, sendResponse) {
9    sendResponse({counter: request.counter+1});
10  });
11