Remote Procedure Call.

A remote procedure call is an inter process communication technique that is used for client-server based applications. It is also known as a subroutine call or a function call.

• A client has a request message that the RPC translates and sends to the server. This request may be a procedure or a function call to a remote server. 
• Remote Procedure Call (RPC) is a powerful technique for constructing distributed, client-server based applications.
• When the server receives the request, it sends the required response back to the client. 
• The client is blocked while the server is processing the call and only resumed execution after the server is finished.
• It is based on extending the conventional 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.

Procedure can be completed as.

• The client stub is called by the client.
• The client stub makes a system call to send the message to the server and puts the parameters in the message.
• The message is sent from the client to the server by the client’s operating system.
• The message is passed to the server stub by the server operating system.
• The parameters are removed from the message by the server stub.
• Then, the server procedure is called by the server stub.

Advantages of Remote Procedure Call

• Remote procedure calls support thread oriented and process oriented  models.
• It has high security because the internal message passing mechanism of RPC is hidden from the user.
• The effort to re-write and re-develop the code is minimum.
• Remote procedure calls can be used in both distributed environment as well as the local environment.
• Many of the protocol layers are omitted by RPC to improve performance.

Disadvantages of Remote Procedure Call

• The remote procedure call is not a standard it is a concept that can be implemented in different ways. 
• It is interaction based only so there is no flexibility in RPC for hardware architecture. 
• The implementation of RPC costly.