Java DatagramSocket在繁重的网络负载下停止响应

Question

I have a client which needs to listen on a particular port for incoming UDP broadcast messages. I accomplish this by initializing a DatagramSocket object bound to the port with a setSoTimeout of 1500ms.

while (true) {
    try{
        DatagramSocket datagramSocket = new DatagramSocket(PORT);

        byte[] buffer = new byte[BUFF_LEN];
        DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

        datagramSocket.receive(packet);

        [handoff packet to internal buffer to await processing]

    } catch (SocketTimeoutException timeout) {
      ...
    } catch [other exceptions]
}

It's pretty textbook and everything works just fine; however during a recent network load test I discovered that my application was not receiving certain datagrams, and the problem worsened the more congested the network got.

Digging further I found that the timeout was triggering each time the the .receive() was called - almost as if there was nothing arriving on the port. However running Wireshark on the same machine shows that this is not true , and well-formed packets of expected size and content are arriving as usual. Somehow the datagrams just weren't finding their way to the application layer.

Ramping down the network traffic immediately alleviates this issue, and the Java application is immediately able to receive and process packets as usual.

Can anyone shed some light into what could possibly be the issue here, or what I can do further to troubleshoot this problem?

Thanks so much.

Answer 1

UDP flood protection on a software firewall perhaps?

Also, UDP is an unreliable protocol by design. It could be that the network layer is discarding packets due to load.

Answer 2

如果数据包到达主机，如果套接字发送缓冲区已满，主机仍可以将其丢弃，这是在应用程序无法跟上输入的情况下发生的。

Answer 3

I don't often program in Java, so maybe I'm missing something here, but why are you calling new DatagramSocket inside the loop? It seems like that would create a new socket for every datagram, which would quickly exhaust system resources.