How RPC Works

Resolving The Problem

RPC
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Client Side
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There are RPC clients that wish to make a remote procedure call to a different machine. These clients need to know the RPC number for the requested service to be able to make the call. (This data is stored in the Registry for DCS Manifest Client.)

A connection is made to a known RPC query daemon brought up on all servers supporting RPC. (This is documented in /etc/services as port 111.) Once the connection is made to port 111 of the destination IP, the client queries it as to what port to ask for service for "MyRpcNumber". The Server at port 111 replies this query with "MyPCPortNumber" for "MyRPCNumber". The Client then makes a connection to the port "MyRPCPortNumber" and starts communication.

Server Side
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Programs which are RPC service providers register with "portmap" (the querying daemon). While registering, the program provides the "MyRPCNumber" and can optionally request for itself to be assigned a specific port for listening. If the requested port is free, "portmap" acknowledges the registry for future connections. If no specific port number is requested, "portmap" assigns a random port number for the Service.

When any client desires to execute an RPC, it first checks against "portmap" at port 111 and asks for the port number where the RPC number is available.