# MessagePortMain `MessagePortMain` is the main-process-side equivalent of the DOM [`MessagePort`][] object. It behaves similarly to the DOM version, with the exception that it uses the Node.js `EventEmitter` event system, instead of the DOM `EventTarget` system. This means you should use `port.on('message', ...)` to listen for events, instead of `port.onmessage = ...` or `port.addEventListener('message', ...)` See the [Channel Messaging API][] documentation for more information on using channel messaging. `MessagePortMain` is an [EventEmitter][event-emitter]. ## Class: MessagePortMain ### Instance Methods #### `port.postMessage(message, [transfer])` * `message` any * `transfer` MessagePortMain[] (optional) Sends a message from the port, and optionally, transfers ownership of objects to other browsing contexts. #### `port.start()` Starts the sending of messages queued on the port. Messages will be queued until this method is called. #### `port.close()` Disconnects the port, so it is no longer active. ### Instance Events #### Event: 'message' Returns: * `messageEvent` Object * `data` any * `ports` MessagePortMain[] Emitted when a MessagePortMain object receives a message. #### Event: 'close' Emitted when the remote end of a MessagePortMain object becomes disconnected. [`MessagePort`]: https://developer.mozilla.org/en-US/docs/Web/API/MessagePort [Channel Messaging API]: https://developer.mozilla.org/en-US/docs/Web/API/Channel_Messaging_API