Address reuse not working on new Java Runtime Environment

Question

I am using the following Code for Checking Address Resusability:-

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;


public class CheckBind {

public static void main(String[] args) {

    Thread serverThread = new Thread(new Runnable() {

        @Override
        public void run() {
            try
            {
                ServerSocket server = new ServerSocket();
                server.setReuseAddress(true);
                server.bind(new InetSocketAddress("127.0.0.1", 2000));
                System.out.println("Server Listen: "+server.getLocalSocketAddress());

                while(true)
                {
                    Socket client = server.accept();
                    System.out.println(""+client.getRemoteSocketAddress());
                    System.out.println(""+client.getLocalSocketAddress());
                }
            } 
            catch (IOException e) 
            {
                e.printStackTrace();
            }

        }
    });

    serverThread.start();

    try {
        Thread.sleep(5000);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    while(true)
    {
        Socket client = new Socket();
        try 
        {
            client.setReuseAddress(true);
            client.bind(new InetSocketAddress("127.0.0.1", 2000));
            client.connect(new InetSocketAddress("127.0.0.1",4000));
            System.out.println("Client Connect: "+client.getRemoteSocketAddress());
            break;
        } 
        catch (IOException e) 
        {
        // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }






}

}

This worked fine on Windows 7, 64bit And I used JRE 7U5 [1.7 Update 5] 32Bit Version. [Considering A Server is already Running on 127.0.0.1:4000]

But When I try the same with newer versions of JRE , like I checked on JRE 7U60 32bit and JRE 7U72 64bit it gives a JVM_Bind Exception. Which basically negates the whole purpose of using setReuseAddress(true) OPTION.

Kindly help on how to fix this issue.

Thanks & Regards

Papillon

Answer 1

The javadocs for setReuseAddress say:

When a TCP connection is closed the connection may remain in a timeout state for a period of time after the connection is closed (typically known as the TIME_WAIT state or 2MSL wait state). For applications using a well known socket address or port it may not be possible to bind a socket to the required SocketAddress if there is a connection in the timeout state involving the socket address or port.

Enabling SO_REUSEADDR prior to binding the socket using bind(SocketAddress) allows the socket to be bound even though a previous connection is in a timeout state.

But what you are doing does not match this use-case. You are not attempting to bind while some other socket is closing. You are actually trying to bind while another socket is open.

---

What puzzles me is why your test actually worked on older JREs. It might be a JVM bug ...

Maryannemarybella

Can you suggest some way for achieving this functionality? I am working on a p2p chat application and want to perform a NAT translation to create a direct TCP connection between the 2 users who are behind different NATs. – Papillon

I don't think it is possible. – Maryannemarybella