[CentOS] Centos 6 Airprint using CUPS/Avahi

Tue Aug 29 15:46:54 UTC 2017
Gary Stainburn <gary at ringways.co.uk>

I've set up another airprint server, but this time I've had to use Centos 6 
because of the age of the kit I'm using - an old 1U rack server.

I've configured CUPS and also Avahi. I've run airprint-generate.py and copied 
the .service files to /etc/avahi/services/

Everything looks fine until I try to print from my IPhone.  I usually test by 
trying to print an email.  As soon as I go to search / select a printer I get 
the following start to appear in /var/log/cups/error_log

E [29/Aug/2017:15:24:07 +0100] Request from "" using invalid Host: 
field "harpo.local:631"

The printer list appears and I can select a printer and click on print. 
However nothing prints off, and I just keep getting the above error message.

I've tried setting 


in /etc/avahi/avahi-daemon.conf but that just prevents Avahi from starting.

Can anyone suggest what I need to do to get Avahi and CUPS to be friendly?