RpcBidiService
A service whose methods accept sub-service inputs, use Flow<T>, or otherwise require bidirectional transport capability.
Extend this instead of RpcHostService when any @KsMethod accepts a @KsService type as input, or uses Flow<T> (which internally bridges through a bidirectional sub-service protocol).
Only bidirectional transports (WebSocket, raw sockets, JNI) can host RpcBidiService instances.