Java Reference
In-Depth Information
Example 5•9: Server.java (continued)
out.close();
in.close();
}
}
/**
* This service demonstrates how to maintain state across connections by
* saving it in instance variables and using synchronized access to those
* variables. It maintains a count of how many clients have connected and
* tells each client what number it is
**/
public static class UniqueID implements Service {
public int id=0;
public synchronized int nextId() { return id++; }
public void serve(InputStream i, OutputStream o) throws IOException {
PrintWriter out = new PrintWriter(o);
out.print("You are client #: " + nextId() + "\n");
out.close();
i.close();
}
}
/**
* This is a non-trivial service. It implements a command-based protocol
* that gives password-protected runtime control over the operation of the
* server. See the main() method of the Server class to see how this
* service is started.
*
* The recognized commands are:
*
password: give password; authorization is required for most commands
*
add:
dynamically add a named service on a specified port
*
remove: dynamically remove the service running on a specified port
*
max:
change the current maximum connection limit.
*
status: display current services, connections, and connection limit
*
help: display a help message
*
quit: disconnect
*
* This service displays a prompt, and sends all of its output to the user
* in capital letters. Only one client is allowed to connect to this
* service at a time.
**/
public static class Control implements Service {
Server server; // The server we control
String password; // The password we require
boolean connected = false; // Whether a client is already connected
/**
* Create a new Control service. It will control the specified Server
* object, and will require the specified password for authorization
* Note that this Service does not have a no argument constructor,
* which means that it cannot be dynamically instantiated and added as
* the other, generic services above can be.
**/
public Control(Server server, String password) {
this.server = server;
this.password = password;
}
