I have just pushed an initial release of reflex-libtelnet[1] to Hackage.

reflex-libtelnet wraps libtelnet[2] in a Reflex interface, so that you
can describe data flows through a telnet state tracker using Reflex
Events. Even if you're not using Telnet in 2019, you might find it
interesting as a study in binding Reflex to a callback-oriented
library.

A telnet echo server is provided as an example[3].

Bug reports[4] and questions/patches[5] are welcome on Sourcehut.

Best,

-- Jack

[1]: https://hackage.haskell.org/package/reflex-libtelnet-0.1.0.0
[2]: https://hackage.haskell.org/package/libtelnet
[3]: https://git.sr.ht/~jack/reflex-libtelnet/tree/master/reflex-libtelnet-example/src/Main.hs
[4]: https://todo.sr.ht/~jack/reflex-libtelnet
[5]: https://lists.sr.ht/~jack/reflex-libtelnet-discuss