I'm working on a web app that is accessible to users via multiple platforms from smartphones to desktops which needs to sometimes make a communication between two clients for example if I want my friend to join my network I'd send him a friend request but I want that request to be seen by my friend without him having to refresh the page.
In this scenario which would be a better choice? And also since I want this to work on as many platforms and browsers as possible which has more browser support? Is there a better option?
Some things to keep in mind when making this choice.
Another option may be notifications. All mobile devices now support notifications that can be targeted to an App and a number of browsers have as well. In all cases a connection already exists from the client to the messaging center (Apple, Google, Microsoft, etc) and all notifications are sent over this channel.
Here's a good overview of WebSockets vs. SSE: http://www.html5rocks.com/en/tutorials/eventsource/basics/