On Jan 17, 2010, at 10:45 PM, Daniel Griffin wrote:
> Here are two tiny apps. They run perfectly on OSX and error like this on
> windows:
>
> Log conenction [Failure instance: Traceback (failure with no frames): <class
> 't
> wisted.internet.error.ConnectionLost' Connection to the other side was lost in
> a non-clean fashion.
> ] Log conenction [Failure instance: Traceback (failure with no frames):
> <class
> 'twisted.internet.error.ConnectionLost' Connection to the other side was lost
> in a non-clean fashion.
Ah. This is very simple, and luckily has nothing to do with threads.
The simplest explanation is that these errors are showing up because you are
printing them out :). If you stop printing them out, they won't show up.
More specifically: You generally shouldn't worry about "clean" vs. "non-clean"
connection shutdown. There are lots of things that can cause "clean" shutdowns
to still lose data, and there are many cases where a "non-clean" shutdown is
actually fine. Your application protocol should be framing messages such that
you can tell which ones have been responded to.
That said, what's going on here is pretty simple. A "clean" shutdown is,
broadly speaking, when both ends of the TCP connection agree on where the
stream of bytes begins and ends. I send you some data, you read all of it, I
shut down the connection, you shut down the connection. If I send you some
data, and you *don't* read all of it, then I shut the connection down, the
result will be a "non-clean" shutdown, because there is still data outstanding
when the connection dies.
In this case, you are calling recv(5) in your server, but your client is
writing "RESPOND" to its transport. As you can see,
>>> len("RESPOND")
7
"RESPOND" is more than 5 bytes.
If you were using Twisted for your server, this wouldn't happen because Twisted
always reads all the bytes that are available and delivers them to dataReceived.
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