- opt) connection validation message sends max paylaod size
- readSize checks if size is in limits of size_t?

        // should be called without any lock hold
        // TODO in Java as in C++ ? reportChannelStateChange();

- searching of channel with server address specified

- void transportUnresponsive() { not implemented (also in Java)
- complete authNZ
- improve RPCClient (as it is in Java)