如何设置Socket UDP下面的缓冲区大小？ C＃

Question

As we know for UDP receive, we use Socket.ReceiveFrom or UdpClient.receive

Socket.ReceiveFrom accept a byte array from you to put the udp data in.

UdpClient.receive returns directly a byte array where the data is

My question is that How to set the buffer size inside Socket. I think the OS maintains its own buffer for receive UDP data, right? for eg, if a udp packet is sent to my machine, the OS will put it to a buffer and wait us to Socket.ReceiveFrom or UdpClient.receive, right?

How can I change the size of that internal buffer?

I have tried Socket.ReceiveBuffSize, it has no effect at all for UDP, and it clearly said that it is for TCP window. Also I have done a lot of experiments which proves Socket.ReceiveBufferSize is NOT for UDP.

Can anyone share some insights for UDP internal buffer???

Thanks

I have seen some posts here, for eg,

http://social.msdn.microsoft.com/Forums/en-US/ncl/thread/c80ad765-b10f-4bca-917e-2959c9eb102a

Dave said that Socket.ReceiveBufferSize can set the internal buffer for UDP. I disagree.

The experiment I did is like this:

27 hosts send a 10KB udp packet to me within a LAN at the same time (at least almost). I have a while-loop to handle each of the packet. For each packet, I create a thread a handle it. I used UdpClient or Socket to receive the packets.

I lost about 50% of the packets. I think it is a burst of the UDP sending and I can't handle all of them in time.

This is why I want to increase the buffer size for UDP. say, if I change the buffer size to 1MB, then 27 * 10KB = 270KB data can be accepted in the buffer, right?

I tried changing Socket.ReceiveBufferSize to many many values, and it just does not have effects at all.

Any one can help?

Answer 1

I use the .NET UDPClient often and I have always used the Socket.ReceiveBufferSize and have good results. Internally it calls Socket.SetSocketOption with the ReceiveBuffer parameter. Here is a some quick, simple, code you can test with:

public static void Main(string[] args)
{
  IPEndPoint remoteEp = null;
  UdpClient client = new UdpClient(4242);
  client.Client.ReceiveBufferSize = 4096;

  Console.Write("Start sending data...");
  client.Receive(ref remoteEp);
  Console.WriteLine("Good");

  Thread.Sleep(5000);
  Console.WriteLine("Stop sending data!");
  Thread.Sleep(1500);

  int count = 0;
  while (true)
  {
    client.Receive(ref remoteEp);
    Console.WriteLine(string.Format("Count: {0}", ++count));
  }
}

Try adjusting the value passed into the ReceiveBufferSize. I tested sending a constant stream of data for the 5 seconds, and got 10 packets. I then increased x4 and the next time got 38 packets.

I would look to other places in your network where you may be dropping packets. Especially since you mention on your other post that you are sending 10KB packets. The 10KB will be fragmented when it is sent to packets the size of MTU. If any 1 packet in the series is dropped the entire packet will be dropped.

Answer 2

The issue with setting the ReceiveBufferSize is that you need to set it directly after creation of the UdpClient object. I had the same issue with my changes not being reflected when getting the value of ReceiveBufferSize.

UdpClient client = new UdpClient()
//no code inbetween these two lines accessing client.
client.Client.ReceiveBufferSize = somevalue