Question

我正在尝试从服务器端口2020读取一些数据包。我运行了tcpdump -r eth1端口2020，可以发现udp数据包正在进入端口。以下是截图：

但是当我尝试从java代码中读取这些数据包时，我没有得到任何数据。以下是我的java代码：

package packetreceiver;

import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketException;
import java.net.UnknownHostException;

import main.Main;
import propertyfilereader.PropertyFileReader;

import org.apache.log4j.Logger;

import com.sun.jmx.snmp.SnmpMessage;

import alarmprocessor.AlarmProcessor;

public class UDPPacketReceiver extends Thread {
    private DatagramSocket socket = null;
    private Logger logger = Logger.getLogger(UDPPacketReceiver.class);
    public boolean dynamicKey = false;

    private UDPPacketReceiver() {
        try {

            logger.debug(" port : " + Main.orgPort);
            logger.debug(" ip : " + Main.orgBindIPStr);
            logger.debug("creating socket");

            socket = new DatagramSocket(null);
            //socket = new DatagramSocket(38567);
            InetSocketAddress address = new InetSocketAddress(2020);
            socket.bind(address);

            logger.debug("Receiver Socket created successfully");
        } catch (Exception e) {
            logger.fatal("Exception at creating socket ", e);
            logger.fatal("Exiting successfully ");
            System.exit(0);
        }
        this.running = true;
    }

    static UDPPacketReceiver instance = null;

    public static UDPPacketReceiver getInstance() {
        if (instance == null) {
            createInstance();
        }
        return instance;
    }

    boolean running = false;

    private static synchronized UDPPacketReceiver createInstance() {
        if (instance == null) {
            instance = new UDPPacketReceiver();
        }
        return instance;
    }

    public void run() {

        byte[] data = new byte[2048];
        DatagramPacket packet = new DatagramPacket(data, data.length);

        while (this.running) {
            try {
                logger.debug("waiting for received data");
                this.socket.receive(packet);
                int length = packet.getLength();
                logger.debug("length:"+length);
                logger.debug("data:"+new String(packet.getData()));         

            } catch (Exception e) {
                if ((this.socket == null) || (this.socket.isClosed())) {
                    this.running = false;
                } else {
                    this.logger.fatal("Error in receiving UDP packet:", e);
                }
            }
        }
    }

    public void shutdown() {
        this.running = false;
        try {
            if ((this.socket != null) && (!this.socket.isClosed())) {
                this.socket.close();
            }
        } catch (Exception localException) {
        }
        this.socket = null;
    }
}

我在stackeoverflow和其他帖子中搜索过但找不到任何解决方案。你能帮我吗？

此致坦维尔

Answer 1

使用netstat命令检查您的应用程序是否实际绑定到正确的IP /接口：

> sudo netstat -tunlp | grep 2020

在linux中运行。

您也可以更改此行：

    InetSocketAddress address = new InetSocketAddress(172.22.49.116, 2020);

Java代码不会在特定端口中获取udp数据包

1 个答案: