- MAX limit for the number of concurrent OPEN Sockets supported ?
This depends entirely on your environment, your application, and its configuration. Socket.IO has many potential transports, some of which don't even require a persistent connection. There is no simple answer to this question, and nor should there be. This is the wrong question to ask. In a usual scenario, Socket.IO isn't going to be your bottleneck... your application itself will be. What you should be asking about is how to scale your application as you grow... and the answer to that is dependent on the specifics of how your application works.
- Guidelines / extra care to be taken to fine-tune the Node Server for Production.
There are entire books on this. Start with the Node.js documentation.
- Does socket.io ensure message deliver ?
Socket.IO when used in default configuration is a reliable transport. Of course things can always get lost... it's the internet after all... but yes, retries will happen. I've found this is one of the best parts of Socket.IO, is that if you need to ensure a message is going to get there, it does its best to do that.
Also are there any node-modules which when installed leverage this feature ?
What feature?
- In case socket.io does not support message delivery; how can I ensure that the message was sent and received successfully to the intended person ?
Yes, you can deliver messages with Socket.IO... that's sort of the whole point. As far as whether data made it to the right person, you just need to send it to the right place. Remember though that someone else could always be sitting at the computer....
