[Retric]

That does not require an open port on the printer connecting to the public internet. https://support.google.com/a/answer/3179170?hl=en

Is Port 5222 required inbound for the print server? No, only 5222 outbound is required.

443 TCP (HTTPS), with connections to: https://www.googleapis.com/* https://accounts.google.com/* https://www.google.com/cloudprint/*

5222 TCP (XMPP, using STARTTLS), with a persistent connection to: talk.google.com