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PubNub is considered a Web Push Engine able to push (or stream) any textual data in real-time data push to any types of clients across the Internet. PubNub solves all the complexity of pushing data in a scalable, secure, efficient, reliable and portable way. On the client side, APIs are provided so that it is very easy to build Bidirectional Data Push Apps (transforming your existing client or creating a new one from scratch). A powerful HTML5 library makes it possible to push data updates to Mobile Phones, Tablets and Web Pages in real-time data push through a zero-install client.
 
PubNub is also referred to as a web data push service with Reverse AJAX capabilities which allows you to send data to clients with BOSH Comet technology. This removes the need to constantly poll for new updates in the app. Other associated terms are: browser push, websockets, web data push, data push, real-time push and push notifications.
 
Objective-C, Java, PHP, JavaScript, Python, Ruby, Erlang, C#, .NET and more are provided for mobile phones and tablets such as Android and iPhone for Web Data Push. Every web browser is supported for web browser push.
 
Basically, PubNub can be considered a publish/subscribe middleware based on the standard HTTP 1.1 protocol.
 
PubNub allows you to securely connect mobile phones, tablets, laptops, desktops and other clients outside of your cloud. PubNub provides the connectivity from your cloud to push data to end clients (phones, tablets, laptops and servers). This is called Real-time Data Push, or Push Notifications.
 
PubNub removes the need for your client apps to constantly poll your cloud for new updates. So you can push data from a Server to a Client. And also you may push data from one Server to another Server, just like Azure ServiceBus ESB.
 
Another option is available for a Mobile Phone to Push Data to another Mobile Phone or any endpoint. With PubNub this becomes easy using the two basic Publish/Subscribe APIs.
 
Additionally PubNub provides automatic Broadcasting. When multiple clients/servers/phones are subscribed to a single channel, each endpoint receives a published message simultaneously.