A White Board Project using Java RMI

The following files are written by me. All others are generated.

java7370.sh   // bash file, do: source java7370.sh
Invoke.java   // support methods 
LineCoords.java // public data structure for a line 
LinesFrame.java // our little window of lines 
LinesFrameImpl.java // implementation of window of lines 
WbAdmin.java         // interface of wbadministrator 
WbServer.java // interface of WhiteBoard server 
WbClient.java // interface of WhiteBoard client 
WbClientImpl.java // implementation of WhiteBoard client 
WbServerImpl.java // implementation of WhiteBoard server 

Make sure your CLASSPATH includes . and .. . The rmic is similar to rpcgen but examines .class files, not .java files, in producing several _Stub.class files

Make sure you are invoking the proper javac java, et al. On many systems, there are multiple versions of JDK installed. The java javac rmic rmiregistry rmid should all be from the same package and version.

which java # check where your java JVM is located
java -version

You can call wb7370build defined in java7370.sh. This is the simplest way to build, as javac subsumes some of the Makefile features. Before invoking it, make sure you are in the parent dir of *.java files.

JDK installations will have their own system wide java.policy file; e.g., on my machine the full path name is /usr/lib/jvm/jdk1.7.0_45/jre/lib/security/java.policy The SocketPermission s may not be good enough. So, create a ~/java.policy file in your home directory. It can be much more detailed than the one below.

% cat  << EOF > ~/java.policy
grant {
  permission java.net.SocketPermission "*:1024-65535", "connect,accept";
  permission java.net.SocketPermission "*:80", "connect";
};
EOF

Before starting the WB server and clients, do wb7370rmi to establish rmiregistry.

For rmiregistry: If port 1099 is in use already, you need to make corresponding edits in Invoke.java.

There are several ways of running our Java WB program. wb7370run defined in java7370.sh is one such example that starts one server and two clients each on two boards.

Server will print its URL, e.g., //localhost/S1.

In general, to start a client do: % java WhiteBoard.WbClientImpl <idn> <boardnm> <displayMcnm> <URL-of-server> The idn is an arbitrary non-neg integer used as a pseudo process id. An example URL for the server is //localhost/S1. The client will start a LinesFrame.

Or you may invoke these text-interactively from % java WhiteBoard.WbAdmin The disadvantage here is that the stdout is then not seen.

You may find the pj alias defined in java7370.sh useful.

No client draws a line, even in its own window, the moment you click in its window. Instead, the client sends the coordinates to its server, the server informs all clients on this board, including this one, of this update.

pleaseDie(): If we really die in a remote method, the caller will get an exception. So, we make sure the method returns normally, and die a little later. A pragmatic solution.

addClient() occurs in recvDisplayObj()