(1) A program that maps client programs to the port numbers of server programs. A portmapper is used with remote procedure call (RPC) programs.
(2) A service that implements version 2 of the portmapper protocol. See also RPCBIND.
(3) A protocol that specifies how to map client programs to the port numbers of server programs. Multiple versions of this protocol, each specifying a different level of functionality, have been defined.