package util;

import java.io.IOException;
import java.net.ServerSocket;

public class PortUtil {
	public static final int application_port = 3003;

	public static boolean testPort(int port) throws PortException {
		try {
			ServerSocket ss = new ServerSocket(port);
			ss.close();
			return true;
		} catch (Exception e) {
			// TODO Auto-generated catch block
			// e.printStackTrace();
			throw new PortException(port);

		}
	}

	public static void usePort(int port) throws PortException {
		try {
			ServerSocket ss = new ServerSocket(port);
			new Thread() {
				public void run() {
					try {
						ss.accept();
					} catch (IOException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}
			}.start();
			// ss.accept();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			// e.printStackTrace();
			throw new PortException(port);

		}
	}

	public static void check(int port) throws PortException {

		int port80 = port;

		if (!testPort(port80))
			throw new PortException(port80);

	}

}

package util;

public class PortException extends Exception {

	int port;

	public PortException(int port) {
		this.port = port;
	}

	public String toString() {

		String result = String.format("%s 端口被占用", String.valueOf(port));

		return result;
	}
}

    	try {
			PortUtil.usePort(PortUtil.application_port);
		} catch (PortException e1) {
			JOptionPane.showMessageDialog(null, "已经启动");
			return;
		}