Distributed Chat

A distributed chat messenger that uses Bluetooth LE mesh networks.

• Fully decentralized architecture, no server or Internet connection required
• Message caching, delayed transmission
• Public and private end-to-end-encrypted messaging channels
• Voice messages, image, file and contact attachments
• Full simulation environment with configurable nodes, links and much more included
• Cross-platform, portable core

Components

The project consists of the following components:

• DistributedChatKit: The abstract application, platform-independent, transport-independent (uses interface for broadcasting/receiving messages)
• DistributedChatBluetooth: An abstraction over platform-specific Bluetooth LE transports
• DistributedChatApp: The iOS/macOS implementation, uses Bluetooth LE as transport, does not require a server
• DistributedChatCLI: The CLI implementation, uses either HTTP/WebSockets as transport with the simulation server or Bluetooth LE (WIP)
• DistributedChatSimulationProtocol: The high-level JSON-based protocol used between CLI and simulation server
• DistributedChatSimulationServer: The companion server for the CLI, relays messages between connected CLI nodes, provides web-interface for configuring links between nodes
• Scripts: Scripts for launching CLI instances conveniently and for testing the BLE transport

The dependency graph between these packages looks like this:

%%{init: {"flowchart": {"defaultRenderer": "elk"}} }%%
flowchart BT
    subgraph cross-platform
        DistributedChatBluetooth --> DistributedChatKit
        DistributedChatCLI --> DistributedChatKit
        DistributedChatCLI --> DistributedChatBluetooth
        DistributedChatCLI --> DistributedChatSimulationProtocol
        DistributedChatSimulationServer --> DistributedChatSimulationProtocol
    end
    subgraph "Apple platforms"
        DistributedChatApp --> DistributedChatKit
        DistributedChatApp --> DistributedChatBluetooth
    end

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Building and Running

First, make sure to have Swift 5.10+ or newer installed. Recent versions for Ubuntu and macOS can be found here.

Simulation Server

To run the simulation server, navigate into the directory DistributedChatSimulationServer and execute:

swift run

The web interface should now be accessible at http://localhost:8080.

CLI

To start a single instance of the CLI, make sure that the simulation server is running, navigate into DistributedChatCLI and execute:

swift run distributed-chat --name Alice

You can substitute any name for Alice. Once the CLI has started, the chosen name should show up as a node in the simulation server's web interface.

For convenience, there is a bash script for starting multiple instances of the CLI together in a single tmux session. To use it, navigate into the root directory of this repository and run

Scripts/start_clis Alice Bob Charles Dave

...or however many clients you want to start. To stop all clients at once, press Ctrl + B then type :kill-session and press enter.

iOS app

Building and running the iOS app is only possible on macOS, so make sure to have the following available:

• Xcode 15.4+
• Swift 5.10+ (should be included with Xcode)
• optionally an iOS device

The open the DistributedChatApp subdirectory in Xcode and build/run the project.