java.net.Socket ignores buffers size settings for UPD

Name: dfC67450 Date: 03/30/2000



Javadoc for java.net.Socket.setReceiveBufferSize(size) states:

     * For UDP, this sets the maximum size of a packet that may be sent on this
     * Socket.
     *
     * Because SO_RCVBUF is a hint, applications that want to
     * verify what size the buffers were set to should call getReceiveBufferSize().


Socket ignores value set by setReceiveBufferSize call and may receive a packet
of length greater than size returned by getReceiveBufferSize() returns. The
problem may lie in the getReceiveBufferSize(). The same words are acceptable for
[set/get]SendBufferSize methods.

Here is the test demonstrating the bug:
---------------------------------------------
import java.net.*;
import java.io.*;


public class Test {

    public static void main (String args[]){
       

        try {
            DatagramSocket ds = new DatagramSocket(0);
            int port = ds.getLocalPort();
            InetAddress address = ds.getLocalAddress();

            Socket soc = new Socket(address, port, false);
            int sPort = soc.getLocalPort();

            InputStream is = soc.getInputStream();
            OutputStream os = soc.getOutputStream();
            soc.setReceiveBufferSize(4);
            soc.setSendBufferSize(3);
            

            byte data[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

            DatagramPacket p1 = new DatagramPacket(data, data.length, address, sPort);
            DatagramPacket p2 = new DatagramPacket(data, data.length);

            boolean passed = true;

            ds.send(p1);
            int receivedSize = is.available();
            int rbs = soc.getReceiveBufferSize();
            if (receivedSize != rbs) {
                System.out.println("received packet lenght: " + receivedSize);
                System.out.println("ReceivedBufferSize: " + rbs);
                passed = false;
            }
 

            os.write(data);
            ds.receive(p2);
            int sentSize = p2.getLength();
            int sbs = soc.getSendBufferSize();
            if (sentSize != sbs) {
                System.out.println("sent packet length: " + sentSize);
                System.out.println("SendBufferSize: " + sbs);
                passed = false;
            }

            if (passed)
                System.out.println("Test passed");
            else
                System.out.println("Test failed");
        } catch (Exception e) {
            System.out.println(" " + e);
        }
    }
}


------------- output from the test ---------
received packet lenght: 10
ReceivedBufferSize: 4
sent packet length: 10
SendBufferSize: 3
Test failed
---------------------------------------------

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