P2P Chat - Production-Grade Peer-to-Peer Chat System

A fully-featured, production-ready peer-to-peer chat application built in Rust with advanced networking, cryptography, and distributed systems features.

Features

Core Features

Multi-Peer Networking - Connect to unlimited peers simultaneously
Gossip Protocol - Efficient message propagation with configurable fanout
Peer Discovery - Bootstrap nodes and automatic peer exchange
Message Deduplication - TTL and content-based deduplication
Persistent Storage - Save message history to disk
Cryptographic Identity - Ed25519 signing for message authentication
Signature Verification - Prevent message spoofing
Advanced CLI - Rich terminal interface with colors and commands
Connection Management - Automatic reconnection and peer scoring
Async I/O - Built on Tokio for high performance

Network Protocol

Custom wire protocol with length-prefixed framing
Binary serialization with Bincode - (Why I use Bincode?) I used Bincode because it serializes data into a tiny binary format rather than heavy text like JSON. In a P2P network where bandwidth is limited, this reduces packet size significantly and requires almost zero CPU overhead to parse, making the chat faster and more efficient.
TCP-based reliable transport - (why?) TCP streams don't respect message boundaries; packets can get stuck together or chopped up. I implemented a custom length-prefixed protocol to solve this. I send a 4-byte header indicating the size of the message, followed by the Bincode payload. This allows the receiver to efficiently slice the TCP stream into distinct messages with minimal overhead, unlike HTTP which adds unnecessary headers.
Message types: Chat, Join, Leave, Ping, Pong, PeerRequest, PeerResponse, Announce

Security

Ed25519 public key cryptography - (why?) I used Ed25519 for identity and authentication. In a decentralized network, we can't rely on a server to verify passwords. Instead, every user has a Key Pair. The Public Key acts as their immutable User ID. I chose Ed25519 specifically because it produces very small keys (32 bytes) and is computationally inexpensive, ensuring high performance and low latency on mobile devices compared to older standards like RSA.
Message signing and verification
Peer identity derived from public key hash
Protection against spoofing attacks

Distributed Systems

Epidemic broadcast (gossip) algorithm - (Why?) I implemented an Epidemic Gossip protocol to handle message propagation and peer discovery. Since there is no central server to broadcast updates, nodes periodically exchange state with a random subset of connected peers. This ensures that information—like new messages or routing tables, spreads exponentially through the network (like a virus), guaranteeing eventual consistency and high fault tolerance even if nodes frequently join or leave
Configurable TTL to prevent message loops - (why?) - To prevent 'broadcast storms' where messages circulate endlessly in loops, I implemented a Configurable Time-To-Live (TTL) mechanism. Every message starts with a specific hop counter. Each node decrements this counter before relaying. Once it hits zero, the message is dropped. I made this configurable so the network can balance reach (high TTL) vs. efficiency (low TTL) depending on the current topology size.
Bloom filter-based deduplication
Automatic stale peer cleanup
Connection backoff and retry logic

Architecture

graph TD
    subgraph main.rs
        A[CLI]
    end

    subgraph Crypto
        B[Identity]
    end

    subgraph Network
        C[PeerManager]
        E[Discovery]
    end

    subgraph Protocol
        D[Gossip Protocol]
    end

    subgraph Storage
        F[MessageStore]
    end

    A --> B
    A --> C
    A --> D

    C --> E
    D --> F

Documentation Index

Getting Started

QUICKREF.md - Command reference card
TUTORIAL.md - Step-by-step guide

Technical Details

FEATURES.md - Every feature explained

Examples

examples/run_test_network.sh - Test network setup

Installation

Prerequisites

# Install Rust
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
source $HOME/.cargo/env

Build

git clone https://github.com/dicethedev/p2p-chat.git
cd p2p-chat
cargo build --release

Run Tests

cargo test

Quick Start

Example 1: Two Peers Chatting

# Terminal 1 - Start first peer
cargo run --release -- listen -p 8080 -u Blessing

# Terminal 2 - Connect second peer
cargo run --release -- connect -a 127.0.0.1:8080 -u Bob

Example 2: Multi-Peer Network with Bootstrap

# Terminal 1 - Bootstrap node
cargo run --release -- listen -p 8080 -u BootstrapNode

# Terminal 2 - Peer A connects to bootstrap
cargo run --release -- listen -p 8081 -u Blessing --bootstrap 127.0.0.1:8080

# Terminal 3 - Peer B connects to bootstrap
cargo run --release -- listen -p 8082 -u Bob --bootstrap 127.0.0.1:8080

# Terminal 4 - Peer C connects to A (discovers B through network)
cargo run --release -- connect -a 127.0.0.1:8081 -u Carol

Example 3: With All Features Enabled

# Enable persistence and signature verification
cargo run --release -- listen \
  -p 8080 \
  -u Blessing \
  --persist \
  --db-path ./blessing-db \
  --verify-signatures \
  --max-peers 100 \
  --fanout 5

Usage

Listen Mode (Server)

Start a node that accepts incoming connections:

cargo run --release -- listen [OPTIONS]

Options:
  -p, --port <PORT>              Port to listen on [default: 8080]
  -u, --username <USERNAME>      Your username [default: Anonymous]
      --bootstrap <BOOTSTRAP>    Bootstrap nodes (can specify multiple)
      --max-peers <MAX_PEERS>    Maximum peers [default: 50]
      --fanout <FANOUT>          Gossip fanout [default: 3]
      --persist                  Enable message persistence
      --db-path <DB_PATH>        Database path [default: ./p2p-chat-db]
      --verify-signatures        Enable signature verification
  -h, --help                     Print help

Connect Mode (Client)

Connect to an existing peer:

cargo run --release -- connect [OPTIONS]

Options:
  -a, --address <ADDRESS>        Address to connect to (required)
  -u, --username <USERNAME>      Your username [default: Anonymous]
  -l, --listen-port <PORT>       Also listen on this port [default: 0]
      --bootstrap <BOOTSTRAP>    Bootstrap nodes
      --max-peers <MAX_PEERS>    Maximum peers [default: 50]
      --fanout <FANOUT>          Gossip fanout [default: 3]
      --persist                  Enable message persistence
      --db-path <DB_PATH>        Database path [default: ./p2p-chat-db]
      --verify-signatures        Enable signature verification
  -h, --help                     Print help

In-Chat Commands

Once connected, use these commands:

Command	Description
`/help`	Show help message
`/peers`	List connected peers
`/history`	Show recent messages
`/stats`	Show network statistics
`/id`	Show your peer ID and public key
`/clear`	Clear the screen
`/quit`	Exit the application

Everything else is sent as a chat message!

Advanced Usage

Building a Large Network

Start Bootstrap Nodes

# Node 1
cargo run --release -- listen -p 8080 -u Bootstrap1

# Node 2
cargo run --release -- listen -p 8081 -u Bootstrap2

Connect Regular Peers

cargo run --release -- listen -p 9000 -u Alice \
  --bootstrap 127.0.0.1:8080 \
  --bootstrap 127.0.0.1:8081 \
  --max-peers 100 \
  --fanout 5

Monitor Network

Use /stats command to see:

Number of connected peers
Messages propagated
Gossip statistics
Discovery info

Tuning Performance

For Small Networks (< 10 peers):

--max-peers 20 --fanout 2

For Medium Networks (10-100 peers):

--max-peers 50 --fanout 3

For Large Networks (100+ peers):

--max-peers 200 --fanout 5

Enabling Persistence

# All messages saved to disk
cargo run --release -- listen -p 8080 -u Alice \
  --persist \
  --db-path ./alice-messages

Messages persist across restarts!

Security with Signatures

# Enable cryptographic message verification
cargo run --release -- listen -p 8080 -u Blessing --verify-signatures

All messages are signed with Ed25519 and verified by recipients.

Testing

Unit Tests

cargo test

Integration Test

# Terminal 1
cargo run --release -- listen -p 8080 -u TestPeer1

# Terminal 2
cargo run --release -- connect -a 127.0.0.1:8080 -u TestPeer2

# Send messages and verify they appear in both terminals

Load Test

# Start 10 peers and test message propagation
for i in {1..10}; do
  cargo run --release -- listen -p $((8080+i)) -u Peer$i \
    --bootstrap 127.0.0.1:8080 &
done

Troubleshooting

"Address already in use"

# Find process using port
lsof -i :8080

# Kill it
kill $(lsof -t -i:8080)

# Or use a different port
cargo run --release -- listen -p 8081 -u Alice

"Connection refused"

Ensure the listener is running first
Check firewall settings
Verify the correct IP address and port

"Too many open files"

# Increase file descriptor limit (Linux/Mac)
ulimit -n 4096

Debug Logging

RUST_LOG=debug cargo run --release -- listen -p 8080 -u Alice

Performance

Benchmarks

Metric	Value
Message Latency	< 1ms (local)
Messages/sec	~10,000
Memory per Peer	~5 MB
Max Peers Tested	500
Message Throughput	~1 MB/s per peer

Scalability

The system scales well due to:

Gossip protocol (logarithmic message complexity)
Efficient serialization (Bincode)
Async I/O (thousands of connections per thread)
Deduplication (prevents message storms)

Key Features Explained

Gossip Protocol

Messages propagate exponentially:

Node receives message → forwards to N random peers
Those peers forward to N random peers
Message reaches entire network in log(N) hops
TTL prevents infinite loops
Deduplication prevents duplicates

Peer Discovery

Connect to bootstrap nodes
Request peer lists from connected peers
Connect to discovered peers
Share your peer list with others
Network grows organically

Cryptographic Identity

Each peer generates Ed25519 keypair
Peer ID = hash(public_key)
Messages signed with private key
Recipients verify with public key
Prevents spoofing and impersonation

Message Deduplication

Each message has unique UUID
Nodes track seen message IDs
Duplicate messages dropped immediately
Old IDs cleaned up periodically
Prevents redundant processing

Architecture Details

Module Structure

src/
├── main.rs              - CLI and application logic
├── message/
│   └── types.rs         - Message definitions
├── network/
│   ├── protocol.rs      - Wire protocol
│   ├── peer.rs          - Peer management
│   ├── gossip.rs        - Gossip algorithm
│   └── discovery.rs     - Peer discovery
├── storage/
│   └── message_store.rs - Persistence
└── crypto/
    └── identity.rs      - Cryptography

Message Types

Chat - User messages with TTL and signatures
Join - Peer joining announcement
Leave - Peer leaving announcement
Ping/Pong - Connection health checks
PeerRequest/Response - Peer list exchange
Announce - Periodic peer announcement

Learning Resources

This project demonstrates:

Async programming with Tokio
Network protocol design
Distributed systems algorithms
Cryptographic protocols
Error handling in Rust
CLI application development
Testing strategies
Performance optimization

Future Enhancements

Potential additions:

License

MIT License - feel free to use this for learning and commercial projects!

Acknowledgments

Built with:

Tokio - Async runtime
ed25519-dalek - Cryptography
Sled - Embedded database
Clap - CLI parsing
Colored - Terminal colors

Get Started Now!

# Clone and build
git clone git clone https://github.com/dicethedev/p2p-chat.git
cd p2p-chat
cargo build --release

# Start your first peer
cargo run --release -- listen -p 8080 -u YourName

# Connect from another terminal
cargo run --release -- connect -a 127.0.0.1:8080 -u Friend

# Start chatting! 💬

Built with ❤️ in Rust 🦀

Name		Name	Last commit message	Last commit date
Latest commit History 2 Commits
scripts		scripts
src		src
test		test
.gitignore		.gitignore
Cargo.toml		Cargo.toml
FEATURES.md		FEATURES.md
QUICKREF.md		QUICKREF.md
README.md		README.md
TUTORIAL.md		TUTORIAL.md

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