RMI Communication Service

The last section contained already the general contents of a communication service. For this reason this section will treat only the differences and the specialties of the implementation of the RMI (Remote Method Invocation) protocol.

RMI is a client - server protocol to call methods on a remote object somewhere in the internet. The server offers a set of methods (an interface) and makes this public available in the RMI registry. The client asks the registry for a reference to the published interface and then can call the offered methods. RMI is mostly transparent for the client and for the server. This makes it a easy to use mechanism for accessing remote objects.

RMI is the standard protocol in Java for remote calls through the internet. It is included in all JDKs (1.0.2 and higher). The RMI service offered by the Java class libraries exists of the following parts:

RMI Registry

The simple naming facility for RMI. It maintains all server objects exported to it.

Server

The server object is published in the RMI registry and is there available for receiving calls from other programs residing on this or other machines.

Client

The object calling a method on the remote object.