Hey HN! I just released dudirekta, an easy-to-use RPC framework that allows exposing functions on both the client and server. This allows the server to call functions on the client instead of just the other way around, which makes it a good fit for implementing bi-directional streams, P2P systems or replacing message-based protocols with something more robust. Its also completely transport independent, you can use TCP, WebSockets or even WebRTC to connect peers (see the examples).
I'd love to get your feedback :)