Real time chat between users like in social network [Larave + Node + Redis]

I need idea how to make emit and subscribe message between 2 users on secure way.

For example: user1 emit message1 on channel: user1-2 user2 subscribe channel user1-2 and recive message1

How can I be sure user3 will not intercept chat between user1 and user2? How can I be sure user3 will not subscribe channel user1-2?

I am using for this Laravel 5, Node.js, Redis, Socket.io. I just need some idea how to make this secure. I would appreciate if you can add some examples too.

via Chebli Mohamed