Exercise: Actix & Websockets

In this exercise you will learn how to

use a web server with actix & Actors
use websockets to communicate messages between frontend and web server
use the env_logger crate
implement custom message handler(s)

The web server runs at http://localhost:8080. Once started, open the link in a browser. The rudimentary UI allows you to connect to the web server, meaning you will join the chat server. Once connected you can write messages in the text input field. Received messages will be displayed in the text box.

Tasks

Broadcast the client message to all other connected clients
- to see the effect connect at least twice in separate tabs
Implement a custom message to disconnect from the chat server
- you should not receive new messages from other clients thereafter
- notify other clients of disconnect
Check that you do not receive your own chat message back
Add heartbeat logic to remove a client from the chat server after 10s of inactivity (e.g. tab closed)
- keep a time in WsChatSession to compare timeout with
- the actix::AsyncContext::run_interval method is used to run a background job to check if client has timed out
- see std::time::Instant and std::time::Duration to determine the time difference
- use WebsocketContext::ping to ping client

Getting Started

Clone the repository at ferrous-systems/teaching-material. You find the assignment in folder assignments/actix/chat-websockets.

Run the web server with cargo run to start the chat server.

The given dependencies of the Cargo.toml are not the most recent versions due to some incompatibilities. Updating these may not compile the program anymore.

Help

Further documentation

actix-web-actors API documentation, check Message enum
actix::Recipient#do_send API documentation to send a message to an Actor
actix::ASyncContext documentation

Bonus Tasks

Add support to enter & display the client name
- For this you need to adapt the index.html page, remove the visibility:hidden; style from the name input field
- Think about how to distinguish setting the name from sending a text, e.g. using a prefix
- Expand the WsChatSession struct to store the name, adapt code accordingly
- If the name is available output it instead of displaying the text "Someone" in code
What issues might the chat server have?
- What is not working as you would expect?