electron/docs/api/message-port-main.md

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# 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Disconnects the port, so it is no longer active.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.
[`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