There are two types of messages involved in the implementation of an RPC system.
Types of messages
- Call Message
- Reply Message
This message is sent by the client to the server for requesting execution of a particular remote procedure.
The two basic components necessary in a call message are
- The arguments necessary for the execution of the procedure.
- The identification information of remote procedure to be executed.
In addition to this, a call message normally has following fields
- A message type field: To distinguish call messages from reply messages.
- A client identification field: To permit server to check the authentication of client process for executing the concerned procedure.
- A message identification field: To consists of sequence numbers to identify duplicates.
RPC call message format
If the RPC server receives a call message from client,it could be faced with one of the following conditions.
- The specified remote procedure is executed successfully.
- An exception condition occurs while executing the specified remote procedure.
- The server finds that the call message is not intelligible to it.
- The server detects by scanning the clients identifier field that the client is not authorized to use the service.
- The server finds that the remote program, version or procedure number is not available with it.