The RPCBIND program maps RPC program and version numbers to universal addresses, thus making dynamic binding of remote programs possible.
The RPCBIND program is bound to a well-known address of each supported transport, and other programs register their dynamically allocated transport address with it. The RPCBIND program then makes those addresses publicly available.
The RPCBIND program also aids in broadcast RPC. A given RPC program will usually have different transport address bindings on different machines, so there is no way to directly broadcast to all of these programs. The RPCBIND program, however, does have a well-known address. So, to broadcast to a given program, the client actually sends its message to the RPCBIND program located at the broadcast address. Each instance of the RPCBIND program that picks up the broadcast then calls the local service specified by the client. When the RPCBIND program gets the reply from the local service, it sends the reply back to the client.