UDP Multicast Chat Room

UDP multicast provides a mechanism for one-to-many communication in a network. Unlike broadcasting, a multicast may only be received by those subscribed to the particular multicast address of interest. This application implements a basic chat room multicast over a local area network.

Caution

All messages in the chat room are sent over unencrypted UDP multicast channels.

Architecture

For the user interface, this project uses the egui framework. In the back-end, the Tokio runtime powers all asynchronous workloads: networking, synchronization, and task scheduling.

The main thread runs the user interface logic. On a separate networking thread, the Tokio runtime handles incoming and outgoing messages. Information is passed between the two threads via channels.

On startup, the network back-end initializes a socket that binds to 0.0.0.0:3000. The socket then joins the multicast address 224.0.0.69:3000. To prevent multiple instances of the application to bind to the same address (on the same device), the SO_REUSEADDR flag is disabled. All of these values may be tweaked via the command-line interface.

Usage: udp-multicast-chat [-a <addr>] [-p <port>] [--reuse]

Networking options.

Options:
  -a, --addr    multicast address that the socket must join
  -p, --port    specific port to bind the socket to
  --reuse       whether or not to allow the UDP socket to be reused by
                another application
  --help        display usage information

To run the server

# Bind to `0.0.0.0:3000`, then join the multicast address
# `224.0.0.69:3000`, and launch the user interface.
cargo run --release -- --addr 224.0.0.69 --port 3000