Whether the broker should discard any prior session state for this client.
Client identifier; may be empty when the broker assigns one (requires cleanSession).
Keep-alive interval in seconds advertised to the broker (0 disables it).
OptionalpasswordOptional password; encoded as bytes (a string is treated as UTF-8).
OptionalusernameOptional username for credential auth.
OptionalwillOptional Last Will and Testament the broker publishes if the client drops ungracefully.
Fields needed to build a CONNECT packet.