Communicate asynchronously from the main process to renderer processes.
Process: Main
The ipcMain
module is an instance of the EventEmitter class. When used in the main process, it handles asynchronous and synchronous messages sent from a renderer process (web page). Messages sent from a renderer will be emitted to this module.
It is also possible to send messages from the main process to the renderer process, see webContents.send for more information.
channel
.event.returnValue
.event.sender.send(...)
.An example of sending and handling messages between the render and main processes:
// In main process.
const {ipcMain} = require('electron')
ipcMain.on('asynchronous-message', (event, arg) => {
console.log(arg) // prints "ping"
event.sender.send('asynchronous-reply', 'pong')
})
ipcMain.on('synchronous-message', (event, arg) => {
console.log(arg) // prints "ping"
event.returnValue = 'pong'
})
// In renderer process (web page).
const {ipcRenderer} = require('electron')
console.log(ipcRenderer.sendSync('synchronous-message', 'ping')) // prints "pong"
ipcRenderer.on('asynchronous-reply', (event, arg) => {
console.log(arg) // prints "pong"
})
ipcRenderer.send('asynchronous-message', 'ping')
The ipcMain
module has the following method to listen for events:
ipcMain.on(channel, listener)
channel
Stringlistener
FunctionListens to channel
, when a new message arrives listener
would be called with listener(event, args...)
.
ipcMain.once(channel, listener)
channel
Stringlistener
FunctionAdds a one time listener
function for the event. This listener
is invoked only the next time a message is sent to channel
, after which it is removed.
ipcMain.removeListener(channel, listener)
channel
Stringlistener
FunctionRemoves the specified listener
from the listener array for the specified channel
.
ipcMain.removeAllListeners([channel])
channel
StringRemoves listeners of the specified channel
.
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.