Java 获取可用 UDP 端口号的方法-白红宇

Java 获取可用 UDP 端口号的方法

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发布时间：2019-06-23

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Java 获取可用 UDP 端口号的方法。TCP 获取的办法类似于这个。

方法一：如果你不介意获取的端口号范围，可以使用 DatagramSocket 的构造方法定义 0 为其端口号，系统将为其分配一个闲置的端口号：

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

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范围的端口号，最简单的办法就是依次遍历这些端口号直到有一个可用：

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 foundthrow new IOException("no free port found");}

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");

测试代码：

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());DatagramSocket socket3 = getRangePort(new int[] { 3843, 4584, 4843 });System.out.println("__________socket3.getLocalPort():" + socket3.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 foundthrow new IOException("no free port found");}}

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");	}

打印结果：

__________socket.getLocalPort():2156

__________socket2.getLocalPort():3843

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