Notes On Chapter Thirty-Eight -- RPC and Middleware

• 38.1 Introduction
  
  
  • Tools for making client-server software
  
  
• 38.2 Programming Clients and Servers
  
  
  • If one programs with the socket Application Programming Interface (API), it's easy to make errors that are hard to detect, but which can cause big problems.
    
    
  • There are (middleware) tools that can eliminate some of those errors - by generating code automatically ... programs that write programs.
    
    
• 38.3 Remote Procedure Call Paradigm
  
  
  • In the Remote Procedure Call (RPC) approach, the programmer works with a conventional API, and special middleware software generates the code to handle the network communication details.
    
    
  • The effect is that the client software appears to make procedure calls that execute on the server.
    
    
• 38.4 RPC Paradigm:
  
  
  • The programmer
    • designs a conventional program,
    • uses an Interface Definition Language (IDL) to partition the call graph of the program into client and server parts, and
    • uses an RPC tool (middleware) to create software that handles the network communication.
      
      
• 38.5 Communication Stubs
  
  
  • When a call is made to a non-local procedure:
    
    
    • A stub on the client
      
      
      • intercepts the procedure call,
      • gathers (marshals) values for arguments,
      • sends a message across the network to a stub on the server,
      • receives results, and
      • returns results to the caller exactly like a local procedure call would.
      
      
    • The stub on the server
      
      
      • receives the message from the client stub,
      • invokes the desired procedure, and
      • sends the results back to the client stub.
      
      
• 38.6 External Data Representation
  
  
  • Data Conversion Problem: When a client invokes a remote procedure, parameters must be passed from client to server. The two hosts may have different ways of representing data (e.g. big-endian versus little-endian.)
    
    
  • A popular way to deal with this:
    • client converts the data to a standard external data representation (XDR),
    • client transmits to server, and
    • server converts from the XDR to its local representation.
    
    
• 38.7 Middleware And Object-Oriented Middleware
  
  
  • These days programmers frequently use object-oriented programming languages. Consequently we now have middleware that supports distributed objects and remote method invocation as well as remote procedure call.
    
    
  • 38.7.1 ONC RPC
    
    
    • Open Network Computing Remote Procedure Call (ONC RPC, aka Sun RPC)
      
      
  • 38.7.2 DCE/RPC
    
    
    • Open Software Foundation's Distributed Computing Environment (DCE)
      
      
  • 38.7.3 MSRPC
    
    
    • Microsoft Remote Procedure Call (MSRPC)
      
      
  • 38.7.4 CORBA
    
    
    • Common Object Request Broker Architecture (CORBA)
    • CORBA has the ability to create proxies (similar to stubs) at runtime.
      
      
  • 38.7.5 MSRPC2
    
    
    • Microsoft Remote Procedure Call, Second Generation (MSRPC2, aka Object RPC, aka ORPC)
      
      
  • 38.7.6 COM/DCOM
    
    
    • Component Object Model (COM) and Distributed Component Object Model (DCOM)
      
      
  • 38.7.7 Java RMI
    
    
    • Java Remote Method Invocation (Java RMI)
      
      
  • 38.7.8 Jini
    
    
    • "Jini" is not an acronym.
    • Jini supports process migration.
      
      
  • 38.7.9 SOAP
    
    
    • Simple Object Access Protocol (SOAP)
      
      
  • 38.7.10 UDDI
    
    
    • Universal Discovery Description and Integration (UDDI)
    • UDDI is a registry mechanism, not an RPC mechanism.
    • UDDI can be used with RPC mechanisms.
      
      
  • 38.7.11 XML
    
    
    • Extensible Markup Language (XML)
    • Many applications that use RPC also use an XML encoding.
      
      
• 38.8 Summary