Multiplex server for Reveal.js

Essentially, this is @hakimel's original multiplex plugin, stripped down to just the pub/sub socket.io server, without static hosting of the slides.

I point all my Reveal.js presentations to an OpenShift VM (free level) running this socket.io service.

Inspired by @ryanj gist-reveal.

Install on OpenShift:

Sign up for a free OpenShift account
Create a new project, e.g., multiplex
Add a new application: "Add to Project", and select "Browse Catalog"
Under "JavaScript", select "Node.js", latest version (6)
Fill in the app's Name (e.g., multiplex).
- Git repo is https://github.com/seanho00/reveal-multiplex
Select "advanced options", and under "Routing", tick "Secure Route"
Select the "Create" button at the bottom
- The webhook trigger doesn't apply since you don't have control over the source repo in this case.

The route you created should have a long auto-generated hostname; e.g., multiplex-multiplex.7e14.starter-us-west-2.openshiftapps.com. You can access the server from that URL. In the following, replace MULTIPLEX_HOST with that hostname.

Custom domains

You may want to use your own custom domain (e.g., mp.seanho.com), instead of the long auto-generated hostname.

Create a CNAME (using your DNS provider's control panel) pointing to the auto-generated hostname.

You will also need to create another route in the OpenShift control panel (Applications > Routes) using your custom domain.

The SSL cert on OpenShift's edge router won't know about your custom domain, so you may want to consider using CloudFlare's SSL proxy.

Get token for each presentation:

https://MULTIPLEX_HOST/token
Say, e.g., the secret is 000SECRET000, and the SocketID is 000SOCKETID000

Reveal.js config:

Place the following in the presentation's index.html, near the bottom, with the rest of the Reveal.js config:

Reveal.initialize({
	multiplex: {
		url: 'https://MULTIPLEX_HOST/',
		id: '000SOCKETID000',
		secret: Reveal.getQueryHash().s || null
	},
	dependencies: [
        	{ src: 'https://cdn.socket.io/socket.io-2.0.3.js', async: true },
        	{ src: Reveal.getQueryHash().s ?
		  'plugin/multiplex/master.js' :
		  'plugin/multiplex/client.js', async: true }
    ]
})

I prefer to host on GitHub pages, so the presentation URL is something like http://MYNAME.github.io/MYPRESENTATION/

Open master presentation:

http://MYNAME.github.io/MYPRESENTATION/?s=000SECRET000

The 's' argument in the query string gets parsed in the Reveal config into the the multiplex plugin's 'secret' config option, and sent to the socket.io server.