Java 实例- 查看端口是否已使用

import java.net.*; import java.io.*; public class Main { public static void main(String[] args) { Socket Skt; String host = "localhost"; if (args.length > 0) { host = args[0]; } for (int i = 0; i < 1024; i++) { try { System.out.println("查看 "+ i); Skt = new Socket(host, i); System.out.println("端口 " + i + " 已被使用"); } catch (UnknownHostException e) { System.out.println("Exception occured"+ e); break; } catch (IOException e) { } } } }

以上代码运行输出结果为：

……
查看 17
查看 18
查看 19
查看 20
查看 21
端口 21 已被使用
查看 22
查看 23
查看 24
……

也可以指定主机的端口：

Main.java 文件

import java.io.IOException; import java.net.InetSocketAddress; import java.net.Socket; import java.net.SocketAddress; import java.net.SocketTimeoutException; public class Main { public static void main(String[] args) { // 检测本地 80 端口 log(isSocketAliveUitlitybyCrunchify("localhost", 80)); // 检测本地 8080 端口 log(isSocketAliveUitlitybyCrunchify("localhost", 8080)); // 检测本地 8081 端口 log(isSocketAliveUitlitybyCrunchify("localhost", 8081)); // 检测 runoob.com 的 80 端口 log(isSocketAliveUitlitybyCrunchify("runoob.com", 80)); // 检测 runoob.com 的 443 端口 log(isSocketAliveUitlitybyCrunchify("runoob.com", 443)); // 检测 runoob.com 的 81 端口 log(isSocketAliveUitlitybyCrunchify("runoob.com", 81)); } /** * 判断主机端口 * * @param hostName * @param port * @return boolean - true/false */ public static boolean isSocketAliveUitlitybyCrunchify(String hostName, int port) { boolean isAlive = false; // 创建一个套接字 SocketAddress socketAddress = new InetSocketAddress(hostName, port); Socket socket = new Socket(); // 超时设置，单位毫秒 int timeout = 2000; log("hostName: " + hostName + ", port: " + port); try { socket.connect(socketAddress, timeout); socket.close(); isAlive = true; } catch (SocketTimeoutException exception) { System.out.println("SocketTimeoutException " + hostName + ":" + port + ". " + exception.getMessage()); } catch (IOException exception) { System.out.println( "IOException - Unable to connect to " + hostName + ":" + port + ". " + exception.getMessage()); } return isAlive; } private static void log(String string) { System.out.println(string); } private static void log(boolean isAlive) { System.out.println("是否真正在使用: " + isAlive + "\n"); } }

以上代码运行输出结果为：

hostName: localhost, port: 80
IOException - Unable to connect to localhost:80. Connection refused
是否真正在使用: true

hostName: localhost, port: 8080
IOException - Unable to connect to localhost:8080. Connection refused
是否真正在使用: false

hostName: localhost, port: 8081
IOException - Unable to connect to localhost:8081. Connection refused
是否真正在使用: false

hostName: runoob.com, port: 80
是否真正在使用: true

hostName: runoob.com, port: 443
是否真正在使用: true

hostName: runoob.com, port: 81
SocketTimeoutException runoob.com:81. connect timed out
是否真正在使用: false

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