I have to know something. I want to know How many connections FCM & APN allows in parallel. I google it and find the FCM allows 1000 connections in parallel but did not know How many connections APN allows in parallel. I also want that is there any other way to increase the connections in FCM & APN.
t's better not to make any connections in parallel, it is recommended to reuse connections or close the connections after delivering Push notifications.
Also Apple suggests leave a connection open unless you know it will be idle. It appears a rule of thumb is 15 connections max.
Therefore, it's better not to increase the connections in APN. Connections via FCM has only limit of 1000 notifications at one go.
Also, check this SO post for more info.