Context:

A customer network has a proxy server in place, nothing can hit the Internet without going via a proxy.

Issue:

EveryonePrint server needs to be able to reach the Internet to connect to the Google Cloud Print (GCP) infrastructure and publish the shared printer.

Resolution:

It is necessary to setup the Web Proxy information :

• Enter the proxy details under Web Proxy in the Web Print configuration page
• Restart EveryonePrint Web service
• Those proxy settings will now be used in the Google Cloud Print feature as well

Additional proxy server configuration:

Google Cloud Print uses the XMPP protocol for communication.

An HTTP proxy server normally doesn't handle XMPP because XMPP is not HTTP. However the XMPP connection is tunneled through HTTP but for that to work, the proxy server must support CONNECT method.

By default, all common proxy server should support this. If this fails, you'll need to add an access rule that specifically allows port 5222 for the CONNECT method.

In Squid proxy server this is accomplished by (squid.conf):

# add XMPP port and CONNECT method
acl XMPP_port port 5222
acl CONNECT method CONNECT
# allow access
http_access allow CONNECT XMPP_port