Re: [xSocket-develop] Simple Server Sometimes Seeing Data Corruption on Client Side

[Rod M. <rod...@gm...>]

While trying to get a simple test that fails I ran into:

java.lang.NullPointerException:
Exception in thread "xServerPool-1-thread-8" java.lang.NullPointerException
    at org.xsocket.connection.WriteQueue.append(WriteQueue.java:133)
    at
org.xsocket.connection.AbstractNonBlockingStream.write(AbstractNonBlockingStream.java:1060)
    at
org.xsocket.connection.AbstractNonBlockingStream.write(AbstractNonBlockingStream.java:1040)
    at testproject.TestServer.sendMessageToAllClients(TestServer.java:73)
    at testproject.TestServer.onData(TestServer.java:63)
    at org.xsocket.connection.HandlerAdapter.onData(HandlerAdapter.java:132)
    at
org.xsocket.connection.MultithreadedHandlerAdapter.access$201(MultithreadedHandlerAdapter.java:38)
    at
org.xsocket.connection.MultithreadedHandlerAdapter$2.run(MultithreadedHandlerAdapter.java:80)
    at
org.xsocket.SerializedTaskQueue.performPendingTasks(SerializedTaskQueue.java:113)
    at
org.xsocket.SerializedTaskQueue.access$100(SerializedTaskQueue.java:38)
    at
org.xsocket.SerializedTaskQueue$MultithreadedTaskProcessor.run(SerializedTaskQueue.java:139)
    at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:885)
    at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:907)
    at java.lang.Thread.run(Thread.java:619)

Which made me think perhaps I'm lacking some basic understanding, since I
see zero synchronization in the call chain down from connection.write. Am I
supposed to provide this synchronization?

Thanks,
Rod

Here's what my test server looks like:

package testproject;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

import java.net.SocketTimeoutException;

import java.nio.channels.ClosedChannelException;

import java.util.concurrent.ConcurrentHashMap;

import org.xsocket.connection.ConnectionUtils;
import org.xsocket.connection.IConnectHandler;
import org.xsocket.connection.IConnection;
import org.xsocket.connection.IDataHandler;
import org.xsocket.connection.IDisconnectHandler;
import org.xsocket.connection.INonBlockingConnection;
import org.xsocket.connection.Server;


public class TestServer
  implements IConnectHandler, IDisconnectHandler, IDataHandler
{
  public static final String END_OF_MESSAGE_DELIM = new String(new char[] {
0 });
//  public static final String END_OF_MESSAGE_DELIM = "\r";

  public static void main(String[] args)
  {
    try
    {
      final Server server = new Server(6000, new TestServer());
      server.setFlushMode(IConnection.FlushMode.ASYNC);

      ConnectionUtils.start(server);
    }
    catch (Exception e)
    {
      e.printStackTrace();
    }
  }

  public boolean onConnect(INonBlockingConnection connection)
  {
    connection.setAutoflush(false);
    m_Connections.put(connection, Boolean.TRUE);
    return true;
  }

  public boolean onDisconnect(INonBlockingConnection connection)
  {
    m_Connections.remove(connection);
    return true;
  }

  public boolean onData(INonBlockingConnection connection)
    throws IOException, UnsupportedEncodingException
  {
    // reset to read position (if former reads failed) and mark it
    connection.resetToReadMark();
    connection.markReadPosition();

    final String message =
connection.readStringByDelimiter(END_OF_MESSAGE_DELIM);

    connection.removeReadMark();

    sendMessageToAllClients("<received>" + message + "</received>");

    return true;
  }

  private void sendMessageToAllClients(String message)
    throws ClosedChannelException, IOException, SocketTimeoutException
  {
    for (INonBlockingConnection connection : m_Connections.keySet())
    {
      connection.write(message + END_OF_MESSAGE_DELIM);
      connection.flush();
    }
  }

  private final ConcurrentHashMap<INonBlockingConnection, Boolean>
m_Connections = new ConcurrentHashMap<INonBlockingConnection, Boolean>();
}


On Sat, May 3, 2008 at 12:43 AM, Gregor Roth <gre...@go...>
wrote:

> Hi Rod,
>
> would you please submit this as a bug (
> http://sourceforge.net/tracker/?atid=850942&group_id=169583). Please also
> add a junit test, which contains the essential xSocket-related part of your
> client and server-side code.
>
> Thanks
> Gregor
>
> 2008/5/3 Rod Magnuson <rod...@gm...>:
>
>> I've got a simple server that sends/receives null terminated Strings
>> to/from a flash based client.
>>
>>
>> Flush mode is async.
>>
>> I'm using the 2.0 final jar.
>>
>> I'm seeing times when the client is receiving mangled data. The length of
>> the data is correct, just some of the contents are wrong. This does not
>> happen often and is hard to reproduce. When it does happen other clients
>> receive the correct data.
>>
>> I write out the messages with:
>>
>>     String END_OF_MESSAGE_DELIM = new String(new char[] { 0 });
>>     connection.write(message + END_OF_MESSAGE_DELIM);
>>     connection.flush();
>>
>> It could be either client or server. Ideas on how to disqualify the
>> server?
>>
>> Thanks,
>> Rod
>>
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