arpchat

so... you know arp? the protocol your computer uses to find the mac addresses of other computers on your network? yeah. that.

i thought it would be a great idea to hijack it to make a chat app :)

built in two days because i was sick and had nothing better to do.

motivation

1. once a year, i'm on a client isolated network that i want to chat with friends over
2. i'm completely insane
3. i'm a programmer

(i swear, i might actually briefly have a use for this! it might not be entirely useless! ... and other lies i tell myself)

limitations

yes

things i made arpchat do

you can send messages tens of thousands of characters long because i implemented a (naive) generalizable transport protocol on top of arp. there's also a bit of compression.

if you wanted, you could probably split off the networking part of this and use it instead of udp. please don't do this.

not only are join and leave notifications a thing, i built an entire presence discovery and heartbeat system to see an updated list of other online users. ironically, part of this serves a similar purpose to arp itself.

for more information on how this all works technically, check out the little article i wrote.

running

if you actually want to install this for some reason, you can get it from the releases page.

on windows, you probably need npcap. make sure you check "Install Npcap in WinPcap API-compatible Mode" in the installer!

on linux, you might have to give arpchat network privileges:

sudo setcap CAP_NET_RAW+ep /path/to/arpchat

then just run the binary in a terminal. you know it's working properly if you can see your own messages when you send them. if you can't see your messages, try selecting a different interface or protocol!

have any issues? that really sucks. you can make an issue if it pleases you.

building

you don't really want to build this. anyway, it's tested on the latest unstable rust.

on windows, download the WinPcap Developer's Pack and set the LIB environment variable to the WpdPack/Lib/x64/ folder.

cargo build