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Re: [lwip-users] http_sent cb shows 1 byte trailer [RAW]

From: Kieran Mansley
Subject: Re: [lwip-users] http_sent cb shows 1 byte trailer [RAW]
Date: Mon, 10 Aug 2009 14:09:16 +0100

On Mon, 2009-08-10 at 05:50 -0700, Chris Strahm wrote:
> What does the 1 byte length mean?

It's called, I'm guessing, when the other side processes the FIN.  The
sent callback is called as a result of data being ACKed, which means
that buffer space should be available to send.  It just so happens in
this case that the sequence being acked is the FIN to mark the end of
the connection.  This could probably be improved, as I can see it's
confusing and not useful.  Feel free to file a feature request bug on

> Why does close get called twice?

I'm guessing that you're using code based on the httpserver_raw example.
If you look at that source, close_conn() is called for a number of
reasons.  The first is from the http_sent() callback if there's no data
left, so almost certainly being triggered by the behaviour outlined
above.  The second is when it receives a packet and it's either not a
GET request, or it's a NULL pbuf.  You're almost certainly seeing a NULL
pbuf passed to the receive callback which means that the other end has
closed the connection.  This is normal, as you have finished the HTTP
transaction - it's just the way that the other end closing a connection
is signalled through the API.


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