Re: [xSocket-develop] Question: SSL with non-threaded onData() hangs sometimes

[Christian K. <ck...@vx...>]

Hi Gregor,

thanks for your fast reply.
I already tried to send an amendment to my last mail (was rejected by list
server):

Sorry, forgot to mention a few important things:

- Connections are in ASYNC mode as tutorial explains
- both nodes can and probably will send data asynchronously at the same time

  (no "synchronous" protocol behaviour as seen i.e. in HTTP)
- SSL Layer is the standard JSSE implementation, either 1.5.x or 1.6.x made
no
  difference so far

The multi-threaded test-case is on its way. At the moment we're waiting for
the
next hang in non-threaded mode (hope to see something different in the
logs).

Hmm, you say SSL should work in non threaded mode - could it be an issue
(may be
with JVMs SSLEngine) if both nodes are sending a stream of data at the same
time?
I understand that you need a Junit test-case, therefore I would examine the
be-
haviour with two pseudo-clients sending random data to each other
continously.

Best regards,
Christian


________________________________

	Von: Gregor Roth [mailto:gre...@go...] 
	Gesendet: Montag, 26. Mai 2008 13:19
	An: xSo...@li...
	Cc: Christian Kahlo
	Betreff: Re: [xSocket-develop] Question: SSL with non-threaded
onData() hangs sometimes
	
	
	Hi Christian,
	
	have you already tested your code in the multithreaded mode? 
	
	If you call the connection methods only within a call back method
(thread) such as onData() or onConnect(), you will not have to synchronize
method calls on the Connection class. xSocket performs the call back methods
always in a serialized for a given connection. 
	
	Independent of this, SSL should work in a non threaded mode as well
as in a multi threaded mode. It is recommended to set the FlushMode to ASYCN
to avoid deadlocks. Did you done this?
	
	If this doesn't help, you should file a bug. Please add also a JUnit
test based on your code.
	
	Gregor 
	
	
	
	
	2008/5/26 Christian Kahlo <ck...@vx...>:
	


		Hi there,
		
		at first thanks for the good work. I stumbled over xSocket
and
		instantly loved it. ;)
		
		So, I was starting to write a repeater service using SSL.
		That means a client and a server both connect the repeater
and
		identify themselves either as being client or server and to
whom
		they belong. The result is a pair of two connections -
similar to
		the proxy example. (it's all about remote desktop stuff)
		
		Everything is working fine - until some sporadic hang occurs
in the
		onData handler. Because it is non-threaded the whole server
hangs.
		
		The code:
		
		       public boolean onData(INonBlockingConnection c)
		               throws IOException, BufferUnderflowException,
		MaxReadSizeExceededException {
		               Node n = (Node)c.getAttachment();
		
		               if(n != null && n.sessionID != null) {
		                       Node n2 = n.server ?
viewers.get(n.sessionID) :
		servers.get(n.sessionID);
		
		                       if(n2 != null) {
		                               System.out.print((n2.server ?
"S" : "C") +
		c.available() + ">");
		                               // before hang #1
		                               ByteBuffer[] data =
		c.readByteBufferByLength(c.available());
		
		                               System.out.print("<" +
(n2.server ? "S" :
		"C"));
		                               // before hang #2
		                               n2.c.write(data);
		
		                               System.out.println("#");
		                       }
		               }
		
		               return true;
		       }
		
		I identified two positions where the code may hang. The
write hangs far more
		often than the
		read. But as I said - sometimes it's running for hours, even
days. In
		another case it died
		within 3 minutes. :(
		
		Could anyone please give me a hint what to watch out for?
What to tune?
		I supposed some synchronisation cludge with the SSL stack
and modified
		xSocket, so that I
		can deliver my own customized SSLEngine. I forced the
connection to use RC4
		stream-cipher,
		because I thought there may be some length difference issue
due to
		padding/unpadding when
		using a block-cipher - but nothing changed. :-/
		
		Or do I simply _have to_ use multi-threading as soon as I
want to have SSL?
		Did I understand the other threads correctly, that I would
have to
		synchronize on the
		connection objects for each read and write operation when
using
		multi-threading?
		
		Thanks in advance.
		
		Best regards,
		Christian
		
		
	
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