In JDK 1.2, if you get a Socket returned from ServerSocket.accept and call
getInetAddress to get the address of the remote peer, it will return 0.0.0.0,
and if you try to get the port on the remote peer, it will return the local
port on which the ServerSocket was listening.

The bug is due to an error in the platform specific native code for the
java.net.PlainSocketImpl class, although the same error is in both the solaris
and win32 implementations.

The cause of the bug is a few typos from when the PlainSocketImpl class's
native methods were converted to use the JNI. At the end of
Java_java_net_PlainSocketImpl_socketAccept, it writes to the InetAddress of
the ServerSocket (this) instead of accepted socket (socket), and it writes
the ServerSocket's local port into the "port" field of the client Socket
(overwriting what had been correctly put there before) instead of the
"localport" field.

The example class LocalTest given below demonstrates the problem; it says
that the client's address is "0.0.0.0" when it should be "127.0.0.1". It
also says that the client's remote port is 2001 (which is really its local
port) and that its local port is 0.


import java.io.*;
import java.net.*;

public class LocalTest implements Runnable {

    private static final int PORT = 2001;

    private ServerSocket server;

    public LocalTest(ServerSocket server) {
        this.server = server;
    }

    public void run() {
        try {
            Socket socket = server.accept();
            System.out.println("Accepted socket: " + socket);
            InetAddress addr = socket.getInetAddress();
            System.out.println("Client's address: " + addr);
        } catch (IOException e) {
            System.err.println("I/O EXCEPTION OCCURRED:");
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        try {
            ServerSocket server = new ServerSocket(PORT);
            System.out.println("Created server socket: " + server);
            (new Thread(new LocalTest(server))).start();
            Thread.sleep(2000);
            Socket socket = new Socket("", PORT);
            System.out.println("Create client socket: " + socket);
        } catch (Exception e) {
            System.err.println("EXCEPTION OCCURRED:");
            e.printStackTrace();
        }
    }
}