NewMsgServer registers a protocol and returns a new server to declare request and response handlers on.

Item is queue entry used to match responds to sent requests.

MessageServer is a request-response multiplexer on top of the p2p layer.

Message is helper type for `MessegeServer` messages.

Service is the subset of method used by MessageServer for p2p communications.

MessageType is an int32 used to distinguish between server messages inside a single protocol.