I came across the wonderful tutorial from AppCoda on implementing an iOS chat in Swift and using a Socket.io. I have just finished implementing it and it works like a charm as an initial setup for a chat app in iOS. By the way, I upgraded the Node.js server-side with a silly bot-based functionality that answers with the best quotes from the movie Back to the Future.
My contribution in this post is neither another chat tutorial nor another chat code (the guys at AppCode did a very good job with the tutorial page and the full source code at GitHub). I am just publishing the diagram that helped me understand how the different Swift Controllers work together with the SocketIO Manager and, in turn, how this last communicates with the server-side Node.JS code. The diagram is not intended to be a detailed description of the entire application, but rather something that could be described as a pseudo-functional-diagram.
Hope it helps you as well! Happy Coding!