Documentation / Tutorials

Using remote source

This tutorial explains how to create a stream between a source of a machine A and a sink of a machine B. This can be done easily in GraphStream, using the Java RMI technology.

Structure

Package org.graphstream.stream.rmi contains all objects needed:

• RMISink, on which the source of the machine A will be connected,
• RMISource, on which the sink of the machine B will be connected.

machine A	network	machine B
Source  RMISink		RMISource  Sink

RMISink and RMISource are remote objects. Methods of Sink are described in RMISource as remote methods which are called by RMISink. RMISink just contains two remote methods allowing to register or unregister a RMISource. Both being a remote object, they need to be bound with a unique identifier.

The fact that RMISource contains Sink methods can be a bit disturbing. This is because even if a RMISource on a machine B is a source for sinks on the machine B, this RMISource is a sink for the RMISink on the machine A.

The registration of a RMISource on a machine B by a RMISink on a machine A can be done from machine A or machine B by calling the register(url) method of RMISink where url is the rmi url of the RMISource, for example “//machine_b/rmi_source”.

Full example

In this example, a generator on a machine called “machine_a” is connected to a graph on a machine called “machine_b”.

First, RMI registry should have been started on both machines. This can be done by the following code:

try {
	java.rmi.registry.LocateRegistry.createRegistry(1099);
} catch (Exception e) {
	// Already started
}

Code executed on machine_b should look as the following:

RMISource source = new RMISource("source_test");
DefaultGraph graph = new DefaultGraph("g");

source.addSink(graph);
graph.display();

By calling the constructor of RMISource with a string identifier, we automatically bind the source of the local machine to this identifier.

Code executed on machine_a should look as the following:

RMISink sink = new RMISink("sink_test");
sink.register("//machine_b/source_test");

Generator gen = new XXXGenerator();
gen.addSink(sink);

gen.begin();

while (...) {
	gen.nextEvents();
	Thread.sleep(250);
}

gen.end();