Hi,
In CUPS 1.6.x the CUPS broadcasting/browsing mechanism to let print
queues on a server automatically appear on clients was removed, and
instead, CUPS servers do broadcasting of their shared print queues only
by Bonjour, but the CUPS damon dos no Bonjour browsing to let the
server's queues automatically show up on clients.
See
https://blueprints.launchpad.net/ubuntu/+spec/desktop-r-cups-bonjour-browsing
One reason why the author of CUPS, Mike Sweet, dropped CUPS
broadcasting/browsing is that it does not work well on mobile devices
which suspend to save battery power.
Now my idea is the following:
On every modern Linux machine avahi-daemon is running for various
reasons, so it is already present and you can see services in your
network, including CUPS print queues, at any time, for example with
avahi-discover.
This will be made use of using two methods:
1. Print dialogs of both GTK and Qt should browse Bonjour-broadcasted
remote printers and add them to the list of available printers, using
the new cupsEnumDests() function of the CUPS library. I have informed
the upstream maintainers of the print dialogs asking for this feature.
This also eliminates the need of a local CUPS daemon on a machine with
no local print queues, making printing with configuration-less clients
more mobile-friendly.
2. Extra daemon (cups-browsed) for legacy applications not using method
(1). The daemon will browse Bonjour broadcasts of remote printers and
create/remove local raw queues pointing to these printers appropriately.
This recovers the automatic appearing of remote queues in all-CUPS-1.6.x
environments. This extra daemon should be derived from
examples/client-browse-services.c but with the callback function setting
up and removing the local CUPS queues when remote printers appear and
disappear.
Now my questions are:
1. What is the impact of a running avahi-daemon on battery life?
2. Can a system suspend and keep suspended with avahi-daemon running?
3. When waking up from suspend, how quickly does avahi-daemon get
updated on the current state of available services in the network?
4. How would be the impact on battery life of the extra daemon I
mentioned in (2) above?
5. Can a system suspend and keep suspended with the extra daemon running?
6. When waking up from suspend, how quickly does the extra daemon get
updated on the current state of available printers in the network?
I am asking this because one of the development goals for Linux
distributions is mobile, see for example:
https://wiki.ubuntu.com/Nexus7
Till
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