I'm using Google Cloud Messaging and have been working on both the application server side (the server that sends push messages) and the Android side (the smartphone app that receives push messages).
Google used to maintain documentation with some Java code for the application server at this link: http://developer.android.com/google/gcm/server.html
However, that link is now dead. It points to https://developers.google.com/cloud-messaging/ now and does not have any information on implementing the application server, in particular in Java.
Where is the application server documentation now, and where can I find the sample code for it?
Of most importance, I need to know what firewall ports to open on the application server side to connect to Google's servers. There are related StackOverflow messages on GCM ports, but again, they all point to URLs that are now dead.
UPDATE 6/12:
I found cached copies of that webpage using the Wayback Machine: http://web.archive.org/web/*/http://developer.android.com/google/gcm/server.html