electron/docs/api/ipc-main-process.md
2015-03-27 07:46:26 -05:00

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# ipc (main process)
Handles asynchronous and synchronous message sent from a renderer process (web
page).
The messages sent from a renderer would be emitted to this module, the event name
is the `channel` when sending message. To reply a synchronous message, you need
to set `event.returnValue`, to send an asynchronous back to the sender, you can
use `event.sender.send(...)`.
It's also possible to send messages from main process to the renderer process,
see [WebContents.send](browser-window.md#webcontentssendchannel-args) for more.
An example of sending and handling messages:
```javascript
// In main process.
var ipc = require('ipc');
ipc.on('asynchronous-message', function(event, arg) {
console.log(arg); // prints "ping"
event.sender.send('asynchronous-reply', 'pong');
});
ipc.on('synchronous-message', function(event, arg) {
console.log(arg); // prints "ping"
event.returnValue = 'pong';
});
```
```javascript
// In renderer process (web page).
var ipc = require('ipc');
console.log(ipc.sendSync('synchronous-message', 'ping')); // prints "pong"
ipc.on('asynchronous-reply', function(arg) {
console.log(arg); // prints "pong"
});
ipc.send('asynchronous-message', 'ping');
```
## Class: Event
### Event.returnValue
Assign to this to return an value to synchronous messages.
### Event.sender
The `WebContents` that sent the message.