Java 实例 - 查看端口是否已使用

以下实例演示了如何检测端口是否已经使用：

实例 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