Java 擷取可用 UDP 連接埠號碼的方法

        Java 擷取可用 UDP 連接埠號碼的方法。TCP 擷取的辦法類似於這個。

        方法一：如果你不介意擷取的連接埠號碼範圍，可以使用 DatagramSocket 的構造方法定義 0 為其連接埠號碼，系統將為其分配一個閑置的連接埠號碼：

public static DatagramSocket getRandomPort() throws SocketException {DatagramSocket s = new DatagramSocket(0);return s;}

方法二：如果你想使用一套特定範圍的連接埠號碼，最簡單的辦法就是依次遍曆這些連接埠號碼直到有一個可用：

public static DatagramSocket getRangePort(int[] ports) throws IOException {for (int port : ports) {        try {            return new DatagramSocket(port);        } catch (IOException ex) {            continue; // try next port        }    }    // if the program gets here, no port in the range was found    throw new IOException("no free port found");}

測試代碼：

import java.io.IOException;import java.net.DatagramSocket;import java.net.SocketException;public class UdpPortTest {public static void main(String[] args) throws IOException {DatagramSocket socket = getRandomPort();System.out.println("__________socket.getLocalPort():" + socket.getLocalPort());DatagramSocket socket2 = getRangePort(new int[] { 3843, 4584, 4843 });System.out.println("__________socket2.getLocalPort():" + socket2.getLocalPort());}public static DatagramSocket getRandomPort() throws SocketException {DatagramSocket s = new DatagramSocket(0);return s;}public static DatagramSocket getRangePort(int[] ports) throws IOException {for (int port : ports) {        try {            return new DatagramSocket(port);        } catch (IOException ex) {            continue; // try next port        }    }    // if the program gets here, no port in the range was found    throw new IOException("no free port found");}}

列印結果：
__________socket.getLocalPort():2156
__________socket2.getLocalPort():3843
原文連結：http://stackoverflow.com/questions/2675362/how-to-find-an-available-port。