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.
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