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