For protoforce, we provide completely asynchronous server and client SDKs for scala and nodejs, also we suport websockets as a transport. Java sdk is built on

For protoforce, we provide completely asynchronous server and client SDKs for scala and nodejs, also we suport websockets as a transport. Java sdk is built on Futures, so somehow it's async as well. Also we support server-to-client calls, which, effectively, are a better alternative to callbacks.