ipcMain
The ipcMain
module, when used in the main process, handles asynchronous and
synchronous messages sent from a renderer process (web page). Messages sent from
a renderer will be emitted to this module.
Sending Messages
It is also possible to send messages from the main process to the renderer process, see webContents.send for more information.
- When sending a message, the event name is the
channel
. - 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(...)
.
An example of sending and handling messages between the render and main processes:
// In main process.
const ipcMain = require('electron').ipcMain;
ipcMain.on('asynchronous-message', function(event, arg) {
console.log(arg); // prints "ping"
event.sender.send('asynchronous-reply', 'pong');
});
ipcMain.on('synchronous-message', function(event, arg) {
console.log(arg); // prints "ping"
event.returnValue = 'pong';
});
// In renderer process (web page).
const ipcRenderer = require('electron').ipcRenderer;
console.log(ipcRenderer.sendSync('synchronous-message', 'ping')); // prints "pong"
ipcRenderer.on('asynchronous-reply', function(event, arg) {
console.log(arg); // prints "pong"
});
ipcRenderer.send('asynchronous-message', 'ping');
Listening for Messages
The ipcMain
module has the following method to listen for events:
ipcMain.on(channel, callback)
channel
String - The event name.callback
Function
When the event occurs the callback
is called with an event
object and a
message, arg
.
IPC Event
The event
object passed to the callback
has the following methods:
event.returnValue
Set this to the value to be returned in a synchronous message.
event.sender
Returns the webContents
that sent the message, you can call
event.sender.send
to reply to the asynchronous message, see
webContents.send for more information.