On 30/12/14 10:18, Louis Lagendijk wrote:
On Tue, 2014-12-30 at 10:09 +0000, Paul Newall wrote:
I have been digging down into the code, and adding extra debug output.
In my network read function kodakaio_net_read it seems that poll(...) is
indicating that there is data to read, but sanei_ tcp_read(..) then
returns zero bytes.
If there was no data I'd expect poll to timeout, and if there was some
data, sanei_ tcp_read should return it?
But this is the only network read code I have ever written in c so I am
not too confident it is correct.
Paul
A read returning 0 bytes when the fd is ready indicates that the other
side closed the TCP-connection. you probably need to send some form of
keep-alive or close/ the connection when you don't need it and re-open
the connection later.
Louis
Thank you Louis, that was very helpful.
It seems that the scanner initiates keep-alive exchanges every 3 seconds
for around 27 seconds, then it closes the connection.
I had assumed the normal thing would be to open the connection in
sane_open, and close it in sane_close,
but perhaps it's better to open the connection in sane_start, and close
it in sane_cancel.
Or I could leave things more or less as they are, but detect the loss
of connection and reopen it if required.
Paul
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