Re: DatagramSocket receive performance

Robert Klemme <>
Fri, 16 Mar 2007 17:17:53 +0100
On 16.03.2007 16:36, Ron wrote:

On Mar 15, 7:36 pm, Esmond Pitt <>

Can you show us some code?

I certainly can!

I retried the test with a version that does not use swing and does not
create any additional threads. The source is below. I get the exact
same result.

The messsage source (DSP board) is sending UDP packets of 125 bytes to
a PC that is running a C and Java program that do nothing but count
these arrivals and print out message counts every 1000 messages. I
can control the send rate at the source. At 50/messages per second,
the C and Java program are both printing out 1000, 2000, 3000, etc at
the same time, and in addition this also matches the count of sent
messages at the source. I increase to 75/messages per second. The C
program message count continues to match the send count on the DSP
board, but the Java program starts to lag behind (the C program prints
out 1000...the java program prints out 1000 several seconds later).


public class test
   public static final int SERVER_PORT = 4242;

   public static final String SERVER_IP = "";

   public static final int RECV_BUFFER_SIZE = 1024;

   public static void main(String args[])
      int messageCount = 0;
      byte[] recvBytes = new byte[ RECV_BUFFER_SIZE ];
      InetSocketAddress address = new
InetSocketAddress(test.SERVER_IP, test.SERVER_PORT );
      DatagramPacket packet = new DatagramPacket( recvBytes,
      DatagramSocket socket;

         socket = new DatagramSocket();
         socket.connect( address );
         // Send registration message
         byte[] sendBuf = new byte[1];
         sendBuf[0] = 1;
         DatagramPacket sendPacket = new DatagramPacket( sendBuf,
            address );
         socket.send( sendPacket );

         // Wait for registration response
         socket.receive( packet );

         while( true )
            socket.receive( packet );


            if( (messageCount % 1000) == 0 )
               System.out.println( "Messages = " + messageCount );
      catch (IOException ex)

Just some ideas without testing this myself:

I don't know what JVM you use, but trying "java -server" is one option.
  Other than that, since everything is in one method, HotSpot does not
have a chance to kick in. Maybe you can refactor the code to a method,
that receives only 1000 packets and then returns; you could then call
this method in an infinite loop.

Also you might want to reset the packet size after every reception - it
may be that there are issues if you have varying packet sizes.

Kind regards


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