Remote Procedure Calls (RPC) Article
What Is RPC?

RPC is a powerful technique for constructing distributed, client-server based applications. It is based on extending the notion of conventional, or local procedure calling, so that the called procedure need not exist in the same address space as the calling procedure. The two processes may be on the same system, or they may be on different systems with a network connecting them. By using RPC, programmers of distributed applications avoid the details of the interface with the network.
The transport independence of RPC isolates the application from the physical and logical elements of the data communications mechanism and allows the application to use a variety of transports.

How RPC Works?

An RPC is analogous to a function call. Like a function call, when an RPC is made, the calling arguments are passed to the remote procedure and the caller waits for a response to be returned from the remote procedure. Figure below shows the flow of activity that takes place during an RPC call between two networked systems.

The client makes a procedure call that sends a request to the server and waits. The thread is blocked from processing until either a reply is received, or it times out. When the request arrives, the server calls a dispatch routine that performs the requested service, and sends the reply to the client. After the RPC call is completed, the client program continues. RPC specifically supports network applications.

RPC Application Development

Consider an example:

A client server look up in a personal database on a remote machine.Assuming that we cannot access the access the database from the local machine (via NFS).

We use UNIX to run a remote shell and execute the command this way. There are some problems with this method:

* the command may be slow to execute.
* You require an login account on the remote machine.

The RPC alternative is to

* establish an server on the remote machine that can repond to queries.
* Retrieve information by calling a query which will be quicker than previous approach.

To develop an RPC application the following steps are needed:

* Specify the protocol for client server communication
* Develop the client program
* Develop the server program

The programs will be compiled seperately. The communication protocol is achieved by generated stubs and these stubs and rpc (and other libraries) will need to be linked in.