SendPort

Learn communication with SendPort and ReceivePort.

SendPort and ReceivePort

ReceivePort is the channel opened to receive messages. SendPort is the endpoint used to send messages into it. It is obtained via receivePort.sendPort.

Typical flow: the main isolate opens a ReceivePort, passes its sendPort to spawn. The new isolate, when done, replies with sendPort.send(result).

ReceivePort is a Stream; you wait for messages with await for or .first. When done, close it with close().

Two-way communication

For two-way communication between two isolates, each side opens a ReceivePort and sends its sendPort to the other. Each side can then send messages to the other.

Messages are processed in order; a single port receives one message at a time. No extra synchronization is needed.

Large objects are copied; for very large data, TransferableTypedData gives zero-copy transfer.

Exercise Wait for a message with ReceivePort

Make main async. Open a port with var port = ReceivePort();. Send a message to it with port.sendPort.send('merhaba isolate'). Wait for the first message with var msg = await port.first; and print it with print(msg);.

Show example solution

import 'dart:isolate';

void main() async {
  var port = ReceivePort();
  port.sendPort.send('merhaba isolate');
  var msg = await port.first;
  print(msg);
}

Test yourself

Match the port concepts

ReceivePort

Message receiving channel
SendPort

Message sending endpoint
.sendPort

SendPort accessor
.first

First message
Which interface does ReceivePort implement?
- Future
- Iterable
- Stream
- Isolate
Show answer

Stream — ReceivePort is a Stream, yielding messages as a flow.

Sending a message

sendPort.____('merhaba');

Show answer

sendPort.send('merhaba');

Next lesson: compute

We Are Enhancing Your Experience

Cookie Preferences

Strictly Necessary Cookies

Analytical Cookies