public Address(
	string protocol,
	string system,
	string host = null,
	Nullable<int> port = null
)

new : 
        protocol : string * 
        system : string * 
        ?host : string * 
        ?port : Nullable<int> 
(* Defaults:
        let _host = defaultArg host null
        let _port = defaultArg port null
*)
-> Address