一次性发送Android推送通知而不是逐个发送

I am trying to send push notifications to users where GCM IDs are storing in a MySQL DB. The thing is with my code, I am fetching the IDs and sending them one by one inside a while loop. If the number of users is big, that is there are lots of IDs (around 700) the server is giving an Internal Error... while once I make the number less (around 200) the code runs fine and I do not get any error.I am trying to send push notifications to users