Module 30: Websockets

Practice Tasks

Complete these tasks to reinforce what you learned in this module.

Task 1: WebSocket upgrade

Create an axum route GET /ws that accepts a WebSocket upgrade. Use WebSocketUpgrade extractor and return ws.on_upgrade(|socket| async move {}). In the upgrade handler, do nothing (or close immediately). Run the server on 3000.

Expected Output:

A client connecting to `ws://127.0.0.1:3000/ws` can upgrade; the handler runs. Use websocat or a browser to test.

Hint: Use the WebSocketUpgrade extractor; return the result of calling .on_upgrade() with a closure that receives the socket. Register the handler with get(ws) on /ws.

Starter Code:

task.rs

// Task 1: WebSocket upgrade. See tasks/TASKS.md.

fn main() {
    todo!("GET /ws with WebSocketUpgrade, on_upgrade");
}

Task 2: Echo WebSocket

In the WebSocket upgrade handler, split the socket into sender and receiver. In a loop, receive messages with receiver.next().await and send each message back with sender.send(msg).await. Use futures_util::{SinkExt, StreamExt}. Break on send error or when stream ends.

Expected Output:

A client that sends text messages receives the same messages back (echo).

Hint: Split the socket into sender and receiver (see the example). Use a loop that receives messages (from the stream) and sends each one back. You’ll need StreamExt and SinkExt from futures_util.

Starter Code:

task.rs

// Task 2: Echo WebSocket. See tasks/TASKS.md.

fn main() {
    todo!("Receive and send back messages in WebSocket handler");
}