CS6223 Distributed Systems : Server binding : rpcbind -- port mapper
SUN RPC --- ONC+ Developer's Guide
Server binding : rpcbind -- port mapper
HOW the server registers itself with its local port mapper and HOW the client discovers the value of this port.
1. We first note that ANY host running an RPC server must be running the port mapper. The port mapper is assigned TCP port 111 and UDP port 111, and these are the only fixed Internet port assignments for Sun RPC.
2. RPC servers always bind an ephemeral port and then register their ephemeral port with the local port mapper.
3. When a client starts, it must first contact the port mapper on the server's host, ask for the server's ephemeral port number, and then contact the server on THAT ephemeral port.
4. The port mapper is providing a NAME SERVICE whose scope is confined to that system.
excerpted from Richard Stevens's Unix Network Programming volume 2, ch.16.