getrpcport() returns the port number for version
versnum of the RPC program
prognum running on
host and using protocol
proto. It returns 0 if it cannot contact the portmapper, or if
prognum is not registered.
prognum is registered but not with version
versnum, it will still return a port number (for some version of the program)
indicating that the program is indeed registered.
The version mismatch will be detected upon the first call to the service.