Remote procedure calls and Java Remote Method Invocation

REMOTE PROCEDURE CALL SYSTEMS have been around since Andrew Birrell and Greg Nelson first proposed them in 1984.1 During the intervening 15 years, numerous evolutionary improvements have occurred in the basic RPC system, leading to improved systems—such as NCS2—that offer programmers more functionality or greater simplicity. The Common Object Request Broker Architecture from the Object Management Group3 and Microsoft’s Distributed Common Object Model4 are this evolutionary process’s latest outgrowths. With the introduction of Java Developer’s Kit release 1.1, a third alternative for creating distributed applications has emerged. The Java Remote Method Invocation system has many of the same features of other RPC systems, letting an object running in one Java virtual machine make a method call on an object running in another, perhaps on a different physical machine. On the surface, the RMI system is just another RPC mechanism, much like Corba and DCOM. But on closer look, RMI represents a very different evolutionary progression, one that results in a system that differs not just in detail but in the very set of assumptions made about the distributed systems in which it operates. These differences lead to differences in the programming model, capabilities, and way the mechanisms interact with the code that implements and built the distributed systems.