Remote procedure call on client server computing
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Remote Procedure Call (RPC) is a protocol enabling one program to request services from another program over a network without handling the network's intricacies. It involves a client that makes procedure calls and a server that processes these requests through stubs that manage communication and results. Developing an RPC application requires specifying communication protocols and creating both client and server programs, which are compiled separately and utilize stubs for message passing.
Remote procedure call on client server computing
- 2. REMOTE PROCEDURE CALL (RPC) Is a protocol that one program can use to request a service from a program located in another computer in a network without having to understand network details. A procedure call is also sometimes known as a function call or a subroutine call. The requesting program is a client and the service- providing program is the server. When program statements that use RPC are compiled into an executable program, a stub is included in the compiled code that acts as the representative of the remote procedure code. the server includes a runtime program and stub that interface with the remote procedure itself.
- 3. RPC
- 4. STUBS When the calling process calls a procedure, the action performed by that procedure will not be the actual code as written, but code that begins network communication. It has to connect to the remote machine, send all the parameters down to it, wait for replies, do the right thing to the stack and return. This is the client side stub. The server side stub has to wait for messages asking for a procedure to run. It has to read the parameters, and present them in a suitable form to execute the procedure locally. After execution, it has to send the results back to the calling process.
- 5. 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. The client makes a procedure call that sends a request to the server and waits. 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.
- 7. RPC APPLICATION DEVELOPMENT To develop an RPC application the following steps are needed: • 1) Specify the protocol for client server communication • 2) Develop the client program • 3) Develop the server program The programs will be compiled separately. The communication protocol is achieved by generated stubs and these stubs and rpc (and other libraries) will need to be linked in.
- 8. STUB
- 9. STUB The client calls the local stub procedure. The stub packages up the parameters into a network message. This is called marshaling. Networking functions in the O/S kernel are called by the stub to send the message. The kernel sends the message(s) to the remote system. This may be connection-oriented or connectionless. A server stub unmarshals the arguments from the network message. The server stub executes a local procedure call. The procedure completes, returning execution to the server stub. The server stub marshals the return values into a network message. The return messages are sent back. The client stub reads the messages using the network functions. The message is unmarshalled. And the return values are set on the stack for the local process.