问题

嘿，大家好，我在Java中遇到了接收UDP数据包的问题。我已经在本地测试过，也在我的大学服务器上测试过。没有抛出任何异常，只是我的客户端没有接收到任何数据包。以下是一些代码片段：

在我的服务器调用的第136行：

```java
ps.PacketUtilSendFileLength();

Packet Service类片段：

public void PacketUtilSendFileLength() throws IOException {
    DatagramPacket packet = null;
    ByteBuffer buffer = ByteBuffer.allocate(8);
    buffer.putLong(file_length);
    buffer.flip();

    if (V6_Mode) {
        packet = new DatagramPacket(hash(buffer.array()), buffer.array().length, Hostv6, PORT);
    } else {
        packet = new DatagramPacket(hash(buffer.array()), buffer.array().length, Hostv4, PORT);
    }

    datagramSocket.send(packet);
}

我的客户端调用：

ByteBuffer buffer = ByteBuffer.allocate(8); // 这两行在主函数的开始处
DatagramPacket FileLength_ACK = new DatagramPacket(buffer.array(), buffer.array().length);
// ...
ps.PacketUtilRecieve(FileLength_ACK);

Packet Service类中的方法：

public DatagramPacket PacketUtilRecieve(DatagramPacket p) {
    try {
        datagramSocket.receive(p);
        return p;
    } catch (IOException e) {
        PacketUtilSendError();
        e.printStackTrace();
    }
    return null;
}

我的服务器正在发送数据包，但是我的客户端从未接收到它，我在这里做错了什么？

完整代码：https://github.com/WeStandUnited/SlidingWindow/tree/master/src

<details>
<summary>英文:</summary>

Hey guys im having trouble recieving UDP packets in java. I&#39;ve currently tested it on locolhost and my uni&#39;s servers. No exceptions are being thrown its just my client not recieve a single packet.  Heres some code :         
 at line 136 in my Server calls 

```ps.PacketUtilSendFileLength();```

// Packet Service class snippet
public void PacketUtilSendFileLength() throws IOException {
DatagramPacket packet = null;
ByteBuffer buffer = ByteBuffer.allocate(8);
buffer.putLong(file_length);
buffer.flip();

    if (V6_Mode) {
        packet = new DatagramPacket(hash(buffer.array()), buffer.array().length, Hostv6, PORT);

    } else packet = new DatagramPacket(hash(buffer.array()), buffer.array().length, Hostv4, PORT);


    datagramSocket.send(packet);

}

My client which calls 

    ByteBuffer buffer = ByteBuffer.allocate(8);// these 2 lines are made at the start of the main
    DatagramPacket FileLength_ACK = new DatagramPacket(buffer.array(),buffer.array().length);
...
ps.PacketUtilRecieve(FileLength_ACK);```

        try {
            datagramSocket.receive(p);
            return p;
        } catch (IOException e) {
            PacketUtilSendError();
            e.printStackTrace();
        }
        return null;
    }

my Server is sending the packet in but my client never recieves it what am i doing wrong here?

full code : https://github.com/WeStandUnited/SlidingWindow/tree/master/src