The current code does not make use of the "protocolVersion" field of the connect request.
We should increment this when making changes to the client protocol. This would allow the server to
accept/deny connections based on looking at the version supported by both the client and server. In some cases
multiple version combinations might be supported (version 1 or 2 or 3 from a client against a "version 3" server,
while v3 client against v2 server might fail). We should be sure to log this to the log4j log during connection (debug).
This might get complex, but if we don't support some combination(s) we should deny the connection and log it
rather than failing later in some unexpected way.