[cups] duplex not working ("Transport endpoint is not connected")

[Johannes Meixner]

Hello,

On Jan 19 14:33 Martin Vogt wrote (excerpt):
> If I change the server to a current version
> the bug reports may be "vice versa", for example:
>
> "Old SLE11 clients won't work with new cups server,
> or the mozilla cups implementation (which works here
> with duplex in RHEL) is incompatible etc.."

On my SLE11 workstation with CUPS 1.3.9 commands like

$ lpoptions -h cups-1.7.5.server -p queue_name -l

still work where "cups-1.7.5.server" is a SLE12
server with CUPS 1.7.5.

On my SLE11 workstation with CUPS 1.3.9 I can still print
from Firefox to that SLE12 server with CUPS 1.7.5.

Accordingly it seems CUPS >= 1.6 on servers
works sufficiently backward compatible with
CUPS < 1.6 on clients.

What does not work sufficiently backward compatible
are CUPS >= 1.6 clients with CUPS < 1.6 servers
(one needs explicitly "/version=1.1" on the clients).


> Is there an interest to fix the reported behaviour?

See
http://www.cups.org/str.php?L4231
in particular the entry "Jan 14, 2013 by Michael Sweet".

Accordingly I think adding "/version=1.1" is the only way
to make CUPS >= 1.6 clients working with CUPS < 1.6 servers.


> How much compatibilty of newer cups with older servers
> is intended/wanted?

I do not know about an official reference documentation
at CUPS upstream about the incompatible changes between
CUPS < 1.6 and CUPS >= 1.6 and how to deal with them.

I collected as much as I noticed at
https://bugzilla.suse.com/show_bug.cgi?id=735404


Kind Regards
Johannes Meixner
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