AirChat
AirChat is a zero-dependency* P2P CLI chat tool that (ab)uses the AirDrop interface to allow chatting across WiFi networks (or no WiFi network).
A RailsCamp AU 20 project.
Features
- Chat to other AirChat users in proximity without being on the same network
- Self-contained - no gems, nothing else to download/install
- Automatically keeps AirDrop active
- Commands:
/nick,/who,/me,/quit - User colours tied to their IPv6 address
Requirements
- OS X with system Ruby 2+ with working AirDrop
- Ruby 2.0 or higher (comes with OS X)
- tcpdump (comes with OS X)
Usage
# Get it
curl -L https://github.com/chendo/airchat/raw/master/airchat.rb > airchat.rb && chmod +x airchat.rb
# or get someone to AirDrop it to you, etc.
# AirChat requires raw access to the /dev/bpf* interface.
# Run using sudo
sudo ./airchat.rb
# OR
# Give permission to /dev/bpf*
sudo chgrp staff /dev/bpf* && sudo chmod g+rw /dev/bpf* # These permissions will reset on reboot
./airchat.rb
How does it work?
AirChat uses the awdl0 interface to talk to other machines with AirDrop active.
However, OS X restricts binding to this interface, and non-AirDrop network traffic is rejected
with ICMP Port Unreachable. AirChat gets around this by using tcpdump to receive UDP data,
as OS X doesn't stop you from sending packets through that interface.
AirChat broadcasts JSON-encoded messages in UDP to ff02::fb on port 1337.
Caveats/TODO
- Messages are transmitted in plain text.
- No direct messaging
- One channel only (you can specify a different port by modifying the source)
- Message delivery is not guaranteed
- No message repeater functionality
License
MIT.
ANSI RGB magic sauce from the paint gem.