Re: [xSocket-develop] Simple Server Sometimes Seeing Data Corruption on Client Side
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Re: [xSocket-develop] Simple Server Sometimes Seeing Data Corruption on Client Side
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From: Rod M. <rod...@gm...> - 2008-05-06 22:28:11
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I've discovered that if I make my client go through a domain & port
forwarding on my router, as opposed to localHost, I can reproduce the
problem in a Java test server to Java test client. Is there any conceivable
explanation about how tcp/ip data can get corrupted?
Thanks,
Rod
On Sun, May 4, 2008 at 11:49 PM, Rod Magnuson <rod...@gm...> wrote:
> While the synchronizing on the connections eliminated the NPE I saw when
> trying to construct a test case, I'm still getting the data corruption
> issue. I can't get my Java to Java test case to repro it, so looks like it's
> on the Flash side, though it's hard to believe there are issues like this in
> XMLSocket. Will continue to investigate.
>
> Thanks again,
> Rod
>
>
> On Sun, May 4, 2008 at 11:38 AM, Rod Magnuson <rod...@gm...>
> wrote:
>
>> Thank you!
>>
>> The tutorial update was great. Appreciate your help.
>>
>> Rod
>>
>>
>> On Sun, May 4, 2008 at 1:04 AM, Gregor Roth <gre...@go...>
>> wrote:
>>
>>> Hi Rod,
>>>
>>> yes, the NonBlockingConnection and BlockingConnection are not thread
>>> safe. This means, you have to synchronize concurrent method calls. xSocket
>>> only guarantees that the call back methods will be executed in a
>>> synchronized, serialized manner.
>>>
>>> The NullPointerException is caused by unsynchronized, concurrent write
>>> calls on the same connection (-> sendMessageToAllClients will be called
>>> concurrently) .
>>>
>>>
>>> May be it would make sense to enhance the ConnectionUtils by a
>>> synchronizedConnection(INonBlockingConnection nbc) and a
>>> synchronizedConnection(IBlockingConnection con) method. But his doesn't help
>>> if concurrent threads will execute code like:
>>>
>>> con.markWritePosition();
>>>
>>> con.write(..);
>>>
>>> con.resetToWriteMark();
>>>
>>>
>>> For this reason I'm not sure if it is a good idea to provide synchronized
>>> connections. This will give the feeling of thread safety which fails if you
>>> using statements like above.
>>>
>>> I updated the tutorial by this subject
>>>
>>>
>>> Gregor
>>>
>>>
>>>
>>>
>>>
>>>
>>> 2008/5/3 Rod Magnuson <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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>>>>>> xSo...@li...
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>>>>>>
>>>>>>
>>>>>
>>>>>
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>>>>>
>>>>>
>>>>
>>>
>>
>
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