Re: Closing Distributed Object connections
Re: Closing Distributed Object connections
- Subject: Re: Closing Distributed Object connections
- From: Wade Tregaskis <email@hidden>
- Date: Thu, 9 Oct 2003 17:34:48 +1000
>
So in step 5, for the first few minutes the NSConnection you are
>
trying to create is returned nil. This could be what you are referring
>
to when you say there is a known bug in which ports cannot be reused
>
immediately after being closed. In this case it is true, but in the
>
example where the clients processes have quit completely before the
>
server quits, there is no delay in creating the new NSConnection on
>
the same port (ie switch steps 3 and 4 in the example above).
Ah, okay. So if you invalidate an NSConnection while it's still being
used (remotely), it doesn't invalidate it's ports until some time later
- presumably some sort of time out.
>
An aside - I find this a bit annoying, it would be nice if the client
>
would be notified if a connection was invalidated, rather than having
>
to wait for a timeout exception.
>
I take a quote from the documentation of NSConnection's
>
NSConnectionDidDieNotification
>
>
"An NSConnection object attached to a remote NSSocketPort object
>
cannot detect when the remote port becomes invalid, even if the remote
>
port is on the same machine. Therefore, it cannot post this
>
notification when the connection is lost. Instead, you must detect the
>
timeout error when the next message is sent."
I think this is very stupid too. I know that you can detect when the
remote side closes a tcp connection, because I've seen it happen in
Carbon applications. It seems OpenTransport was intelligent enough for
this, whereas BSD sockets are not. Then again, I was under the
impression that OpenTransport was implemented as a layer over BSD
sockets...hmmm.
What should be done is that the closing side of the connection should
send a message indicating such, at the DO-protocol level. This would
overcome the apparent sockets bug.
Wade Tregaskis
-- Sed quis custodiet ipsos custodes?
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