Neutral P2P Chat

Peer-to-peer chat built with Rust, libp2p, and an egui/eframe desktop client. A lightweight rendezvous server handles discovery plus a simple username-based auth directory so users can pick who to chat with by name (not by PeerId).

This repo contains two crates:

• server — libp2p rendezvous server with an additional auth request/response protocol ("/auth/1.0"). Maintains a runtime map of username -> PeerId for online users and a simple user database for registration/login.
• client — desktop app using egui. Shows a Login/Register screen, then a chat UI with a username dropdown sourced from the server.

Features

• Username-based directory for selecting peers (self is omitted)
• Stable, case-insensitive alphabetical ordering of usernames
• Live updates: the client refreshes the directory periodically (defaults ~5s)
• Cleanup on disconnect: server removes usernames when clients go offline; clients also send an explicit LOGOUT on close (best effort)
• Configurable rendezvous address via CLI for both server and client

Architecture at a glance

• Transport/protocols: libp2p with TCP, Noise, Yamux, Identify, Ping, Rendezvous, and Request/Response
• Chat protocol: simple request/response exchanging text messages ("/hello/1.0")
• Auth protocol ("/auth/1.0"): plaintext control messages
  • REGISTER:||
  • LOGIN:|
  • LIST → returns LIST:userA=PeerIdA,userB=PeerIdB,...
  • LOGOUT:
• User database: stored on the server (see server/users.xml). Passwords are stored as a SHA-256 hash (demo only; no salt).
• Online directory: in-memory username -> PeerId map updated on login/logout and when connections close.

Build

cargo build

Run

1. Start the rendezvous/auth server (leave it running):

cargo run -p server -- 0.0.0.0:62649

Notes:

• The server listens on the provided ip:port. If omitted, it defaults to 0.0.0.0:62649.
• On startup it prints its PeerId and bound address.

2. Start one or more clients (each in its own terminal):

cargo run -p client -- 127.0.0.1:62649

Notes:

• The client dials the rendezvous server at the given ip:port. Default: 127.0.0.1:62649.
• First screen is Login/Register. After successful auth you’ll see the chat UI.

Using the app

1. Register or Login

• Register succeeds if the username is free; otherwise you’ll see an error.
• Login succeeds only if your current PeerId previously registered that username.

2. Pick a user to chat with

• The top bar shows a “User” dropdown listing online usernames (excluding yourself).
• The list is sorted alphabetically (case-insensitive) and refreshes every few seconds.
• Selecting a user will automatically connect to that peer.

3. Chat

• Type in the bottom input and click Send. Messages appear right-aligned for you (prefixed "You to ...") and left-aligned for incoming messages.

CLI reference

• Server: cargo run -p server -- [ip:port]
  • Default: 0.0.0.0:62649
• Client: cargo run -p client -- [ip:port]
  • Default: 127.0.0.1:62649

Troubleshooting

• Windows: "Access is denied (os error 5)" when building — a running server.exe or client.exe is locking the file. Close the app(s) and build again.
• Windows firewall may prompt on first run. Allow access so peers can listen/dial.
• Don’t see new users immediately? The username list is refreshed periodically (about every 5s). Wait a moment or restart the client if needed.
• If the rendezvous server goes offline, clients will clear the user list and repopulate on reconnect.

Notes and limitations

• Demo-grade auth: passwords are hashed with SHA-256 and stored in users.xml without salt. Do not use this as-is for production.
• The runtime username -> PeerId directory is not persisted. It’s rebuilt from client sessions and cleared on server restart; the user database remains.
• Chat messages are plaintext over the simple request/response protocol (suitable for demos only).

License

See the LICENSE file in this repository.