If you are evaluating options, check out IP Messaging from Twilio:
https://www.twilio.com/docs/tutorials/walkthrough/ip-chat/ios/swift#0
The tutorial above in Swift for iOS (also available for Objective-C) allows you to work with a native SDK while the server side app (yours in Node.js) generates user access tokens to connect to the API.
The code walks you through joining a channel, creating a channel and sending messages.
Note: I do work for Twilio. This quick sample app should at least help you determine what functionality will work best for you.
