The RPC protocol enables remote execution of subroutines across a TCP/IP network. RPC, together with the eXternal Data Representation (XDR) protocol, defines a standard for representing data that is independent of internal protocols or formatting. RPCs can communicate between processes on the same or different hosts.
The RPC protocol enables users to work with remote procedures as if the procedures were local. The remote procedure calls are defined through routines contained in the RPC protocol. Each call message is matched with a reply message. The RPC protocol is a message-passing protocol that implements other non-RPC protocols, such as batching and broadcasting remote calls. The RPC protocol also supports callback procedures and the select subroutine on the server side.
RPC provides an authentication process that identifies the server and client to each other. RPC includes a slot for the authentication parameters on every remote procedure call so that the caller can identify itself to the server. The client package generates and returns authentication parameters. RPC supports various types of authentication, such as the UNIX systems.
In RPC, each server supplies a program that is a set of procedures. The combination of a host address, a program number, and a procedure number specifies one remote service procedure. In the RPC model, the client makes a procedure call to send a data packet to the server. When the packet arrives, the server calls a dispatch routine, performs whatever service is requested, and sends a reply back to the client. The procedure call then returns to the client.
RPC is divided into two layers: intermediate and lowest. Generally, you use the RPC interface to communicate between processes on different workstations in a network. However, RPC works just as well for communication between different processes on the same workstation.
The Portmapper program maps RPC program and version numbers to a transport-specific port number. The Portmapper program makes dynamic binding of remote programs possible.
To write network applications using RPC, programmers need a working knowledge of network theory and C programming language. For most applications, understanding the RPC mechanisms usually hidden by the RPCGEN protocol compiler is also helpful. However, RPCGEN makes understanding the details of RPC unnecessary. The figures in The RPC Interface give an overview of the high-level RPC client and server processes from initialization through cleanup. See the SAMPLES\RPC directory for sample RPC client, server, and raw data stream programs. RPCGEN samples are in the SAMPLES\RPCGEN directory.
For more information about the RPC and XDR protocols, see the Sun Microsystems publication, Networking on the Sun Workstation: Remote Procedure Call Programming Guide , RFC 1057 and RFC 1014.