runtime.onConnectExternal

Fired when an extension receives a connection request from a different extension.

To send a message which will be received by the onConnectExternal listener, use runtime.connect(), passing the ID of the recipient in the extensionId parameter.

The listener is passed a runtime.Port object which it can then use to send and receive messages. The Port object also contains a sender property, which is a runtime.MessageSender object, and which the recipient can use to check the sender's ID.

Syntax

browser.runtime.onConnectExternal.addListener(listener)
browser.runtime.onConnectExternal.removeListener(listener)
browser.runtime.onConnectExternal.hasListener(listener)

Events have three functions:

addListener(callback)

Adds a listener to this event.

removeListener(listener)

Stop listening to this event. The listener argument is the listener to remove.

hasListener(listener)

Checks whether a listener is registered for this event. Returns true if it is listening, false otherwise.

addListener syntax

Parameters

function

A callback function that will be called when this event occurs. The function will be passed the following arguments:

port

A runtime.Port object connecting the current script to the other extension it is connecting to.

Browser compatibility

Examples

In this example the extension Hansel connects to the extension Gretel:

console.log("connecting to Gretel");
var myPort = browser.runtime.connect(
  "[email protected]"
);

myPort.onMessage.addListener((message) => {
  console.log(`From Gretel: ${message.content}`);
});

browser.browserAction.onClicked.addListener(() => {
  myPort.postMessage({content: "Hello from Hansel"});
});

Gretel listens for the connection and checks that the sender is really Hansel:

var portFromHansel;

browser.runtime.onConnectExternal.addListener((port) => {
  console.log(port);
  if (port.sender.id === "[email protected]") {
    console.log("connection attempt from Hansel");
    portFromHansel = port;
    portFromHansel.onMessage.addListener((message) => {
      console.log(`From Hansel: ${message.content}`);
    });
  }
});

browser.browserAction.onClicked.addListener(() => {
   portFromHansel.postMessage({content: "Message from Gretel"});
});