This is an extended version of the chat server from Simon Marlow's Parallel and Concurrent Programming in Haskell. I added support for multiple chat channels, and re-implemented broadcast using a broadcast channel, to avoid a transaction involving an unbounded number of TChans (as suggested in the chapter recap). Hopefully someone finds this code useful.

You can buy the book at the link above, or read it online for free. Here's the relevant section: link.

For noobs:

git clone git@github.com:mitchellwrosen/haskell-chat-server-example.git
cd haskell-chat-server-example
cabal sandbox init
cabal update
cabal install --only-dependencies
cabal run
(in another terminal)
nc localhost 44444