2 JVMs Each want same port

Question

I am working on a new approach to where I need to have a class instantiated which will make use of a port. This class will appear in multiple JVMs. I want to start with port 8100 and add one if the previous is busy.
The function to find a vacant port:
public static String getPort( int seed ) {
     while( true )
          try {
               System.out.println("");
               System.out.println(instanceID + " Checking port " + Integer.toString(seed));
               System.out.println("");
               ServerSocket srv= new ServerSocket(seed);
               srv.close();
               srv=null;
               return seed;
          catch( IOException e ) {     
               seed++;
JVM 1 (each have the getPort() function)
Something mything = new Something(getPort(8100));
This gets 8100 as it should.
JVM 2
Something mything = new Something(getPort(8100));
This gets 8100 and it should NOT. It should get 8101. Is there a better way of getting a port like this?
Thanks,
Steffan

Answer 1

Quite easily done: launch this program repeatedly and see what happens:
import java.io.*;
import java.net.*;
public class SSTest {
    public static void main(String[] args) throws Exception {
        ServerSocket ss = createServerSocket(8100, 8121);
        int port = ss.getLocalPort();
        System.out.println("acquired port " + port);
        Thread.sleep(10 * 1000);
        ss.close();
        System.out.println("closed port " + port);
    static ServerSocket createServerSocket(int initialPort, int ubPort) {
        for(int i = initialPort; i < ubPort; ++i) {
            try {
                return new ServerSocket(i);
            } catch (IOException e) {
                System.out.format(
                    "new ServerSocket(%d) fails: %s%n", i, e.getMessage());
        return null;
}