Connection limitations are based on the client/device/platform. For example, a JavaScript web client is limited to about 40 connections (depending on the browser/version), while the C# API is limited by Microsoft to 2-3 connections. The Java, Python and Ruby APIs are less strict in that regard.

But if you are opening many connections (instantiating multiple instances of PubNub) you should consider why and if it is the best practice for your use case. If in doubt, please contact PubNub Customer Support.