Here you can find the source of getServerPort()
public static int getServerPort()
//package com.java2s; /**//from ww w . j a v a2 s . c o m * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, * software distributed under the License is distributed on an * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY * KIND, either express or implied. See the License for the * specific language governing permissions and limitations * under the License. * */ import java.io.IOException; import java.net.ServerSocket; public class Main { /** * Get a server socket point for server, either TCP or UDP. * @return server socket point */ public static int getServerPort() { int serverPort = 0; try { ServerSocket serverSocket = new ServerSocket(0); serverPort = serverSocket.getLocalPort(); serverSocket.close(); } catch (IOException e) { throw new RuntimeException("Failed to get a server socket point"); } return serverPort; } }