Remote Procedure Call RPC Back born of Network Programming

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Remote Procedure Call (RPC)Back born of Network
Programming
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Objectives

• What is RPC?
• What are the working principles of RPC?
• What is RPC calling Mechanism?
• What are steps for RPC application development?
• What are the consideration of RPC protocol?
• What is the need of XDR filter?
• RPC LIB
• What is state and why it is important?
• High-level RPC applications

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What is RPC?

• RPC is a powerful technique for constructing
  distributed client server applications.
• The executing procedure may not exist in the same
  address space as the calling procedure.
• By using RPC, programmers of distributed
  applications avoid the details of interface with
  the network.
• TCP and UDP supports
• ONC RPCGEN protocol compiler

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Remote versus local procedure calling
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RPC Makes Interprocess Communication Less Painfull

• IPC is an essential part of the clientserver
  model.
• Machines portability
• Socket problem
• ONC RPC and DEC RPC.

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How RPC Works
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How RPC Works (cont.)
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Remote Procedure Calling Mechanism

• A remote procedure is uniquely identified by the
  triple (program number, version number,
  procedure number).
• 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

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Defining the Protocol

• For the protocol you must identify the name of
  the service procedures, and data types of
  parameters and return arguments.
• The protocol compiler reads a definition and
  automatically generates client and server stubs.
• Rpcgen uses its own language (RPC language or
  RPCL) which looks very similar to preprocessor
  directives.
• rpcgen rpcprog.x
• This will generate possibly four files
• rpcprog_clnt.c ? the client stub
• rpcprog_svc.c ? the server stub
• rpcprog_xdr.c ? If necessary XDR (external data
  representation) filters
• rpcprog.h ? the header file needed for any XDR
  filters.

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XDR filter

• The external data representation (XDR) is a data
  abstraction needed for machine independent
  communication. The client and server need not be
  machines of the same type.

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RPCGEN
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What is State and why it is important?

• what happens when they cannot communicate with
  each other?
• What happens when the server crashes while
  executing a service procedure? What does the
  client do? The response depends upon whether a
  server is stateless or stateful.
• A stateless server does not maintain any
  information or state about the clients. Stateful
  servers accumulate client information for remote
  procedure calls and require it to function
  properly

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RPC LIB