The RPC Interface

The RPC model is similar to the local procedure call model. In the local model, the caller places the argument to a procedure in a specified location such as a result register. Then, the caller transfers control to the procedure. The caller eventually regains control, extracts the results of the procedure, and continues the execution.

RPC works in the same way: One thread of control winds logically through the caller and server processes as follows:

• The caller process sends a call message that includes the procedure parameters to the server process and then waits for a reply message (blocks).

• A process on the server side, which is dormant until the arrival of the call message, extracts the procedure parameters, computes the results, and sends a reply message. Then the server waits for the next call message.

• A process on the caller side receives the reply message and extracts the results of the procedure. The caller then resumes the execution.

See the following figures for an illustration of the RPC model: RemoteProcedureCall( Client )

Remote Procedure Call (Server)