local-chat

A browser-based virtual hangout space for local-network events. Works at http://chat.local — no internet, no accounts, no installs needed for visitors.

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Prerequisites

• Raspberry Pi connected to your event WiFi
• Avahi daemon running (usually pre-installed on Raspberry Pi OS — systemctl status avahi-daemon)
• The Pi's hostname set to chat (check with hostname; set with sudo raspi-config → System Options → Hostname)
• Node.js 20 installed via nvm (see Installation)

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Installation

1. Install Node.js (first time only)

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash
source ~/.bashrc
nvm install 20

2. Install dependencies

cd /home/beezoo/local-chat
npm install

3. Install the systemd service

sudo cp local-chat.service /etc/systemd/system/
sudo systemctl daemon-reload
sudo systemctl enable local-chat
sudo systemctl start local-chat

4. Verify it's running

systemctl status local-chat
curl http://localhost

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Accessing the Space

• macOS / Linux / iOS / Android: Open http://chat.local in any modern browser.
• Windows: Windows may need Bonjour Print Services for .local mDNS resolution. Alternatively, find the Pi's LAN IP (hostname -I) and use http://192.168.x.x directly.

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Service Management

# Start / stop / restart
sudo systemctl start local-chat
sudo systemctl stop local-chat
sudo systemctl restart local-chat

# View live logs
journalctl -u local-chat -f

# Check status
systemctl status local-chat

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After Code Changes

cd /home/beezoo/local-chat
# edit files ...
sudo systemctl restart local-chat
# Visitors' browsers will reconnect within a few seconds automatically

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Visitor Guide (quick summary)

1. Connect to the event WiFi
2. Open http://chat.local in a browser
3. Pick a character and type your name → Enter →
4. Walk around with Arrow keys or WASD
5. Chat in the panel on the right; your message appears as a speech bubble above your avatar for ~4 seconds

Mobile users: Chat works but movement controls are keyboard-only — your avatar will appear at a fixed spot in the room.

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Architecture

local-chat/
├── .gitignore
├── package.json
├── server.js                  # Express + Socket.IO server, 20 Hz game loop
├── local-chat.service         # systemd unit
├── README.md
└── public/
    ├── index.html             # Single-page app shell
    ├── css/style.css          # All styles
    ├── js/
    │   ├── characters.js      # Sprite sheet config (6 characters)
    │   ├── entry.js           # Avatar selection + name entry
    │   ├── game.js            # Socket.IO client, rAF loop, lerp interpolation
    │   ├── renderer.js        # Canvas sprite + label drawing
    │   ├── input.js           # Keyboard input, movement, boundary clamp
    │   └── chat.js            # Chat panel + speech bubble overlay
    └── assets/
        └── characters.png     # Kenney Roguelike Characters (CC0)

Real-time flow: Socket.IO WebSocket → server game loop at 20 Hz broadcasts game:state to all clients → clients lerp-interpolate toward server positions each animation frame.

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Capacity

Designed for up to ~30 simultaneous visitors on a local network. Each game:state broadcast at 20 Hz is ~60 KB/s for 30 players — trivial on LAN.

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Credits

Character sprites: Kenney Roguelike Characters — CC0 / public domain