Realtime web libraries - replace hookbox with socket.io or what?

Question

I've got a couple projects that were built using hookbox to manage real-time message passing between web clients and servers. Hookbox was great -- it totally abstracted the transport layer, exposing a simple publish/subscribe interface across different channels with an elegant security system.

Unfortunately the hookbox project has rapidly fallen into disarray due to the original maintainer's unwillingness to even put in the effort to hand off ownership. (Grrr!) So it's hard to consider it a viable platform any more.

What's a good platform for providing real-time communication with web apps? Requirements:

• Works seemlessly cross browser, using HTML5 websockets or COMET as available. Transport choice should be invisible to application layer. I don't care about ancient browsers (IE6)
• Client access from both javascript and server-side systems (i.e. in php / python / ruby) -- this is critical
• Provides a publish / subscribe metaphor with arbitrary payloads
• Allows clients to see what other clients are connected to a channel, i.e. presence
• Fine-grained access control through callbacks to any web application (nice to have)

I've heard that socket.io can do some of this, but I get the sense that it's at a lower layer of the stack. Can it connect to non-javascript libraries? Do auth?

Answer 1

I've had a very good experience with NodeJS and Socket.IO over the last 8 months. The server side component has been very stable for me - I can leave it running with a very high message volume and it's resident memory never really budges above 20MB. So far I've only been able to leave it running for about 4 weeks without terminating the server, but that was only because I needed to update my server side code.

Works seemlessly cross browser, using HTML5 websockets or COMET as available. Transport choice should be invisible to application layer. I don't care about ancient browsers (IE6)

Provides a publish / subscribe metaphor with arbitrary payloads

Socket.IO is also a fantastic piece of software. It under active development, and has a simple pub/sub style abstraction built in using EventEmitter (NodeJS) semantics of 'on' (subscribe) and 'emit' (publish). It is also very transparent on the client side regarding the transport being used. I used it primarily for the straight-up WebSocket support, but it can fall back to Flash based sockets, xhr-polling, and jsonp polling.

Client access from both javascript and server-side systems (i.e. in php / python / ruby) -- this is critical

NodeJS is JavaScript, running on the V8 engine. It has a ton of 3rd party modules that provide nice abstractions as well as interfacing with external components, such as a databases or message queues, among many other things. As far as hitting the system with php/python/ruby, it would work as with hitting any other server. Choose your method of communication (basic TCP/IP, or maybe HTTP POSTs or GETs, or even via filesystem) and NodeJS doesn't really care who is providing the data. Personally, I've implemented a C# client that is working great.

Allows clients to see what other clients are connected to a channel, i.e. presence

It doesn't not have any built in 'presence' logic, though with the built in 'pub/sub' logic already in place in Socket.IO, all you'd have to do is store state on the server so new clients can retrieve existing presence data. I've implemented my own basic pub/sub on the server that retains state, and all together (including the NodeJS server code, and the basic Socket.IO stubs) it was only 50 lines of JavaScript (including whitespace).

Fine-grained access control through callbacks to any web application (nice to have)

Not sure what you mean by 'Fine-grained access control through callbacks to any web application (nice to have)'. The pub/sub event/observer metaphor they have uses callbacks, so you hook specific actions to specific events.

Do auth?

I've had no need, yet, to do any auth for our systems, so I can't speak to it directly. However, if you browse the NodeJS modules you'll notice there are many auth modules available, including LDAP and OAuth, not to mention one module that claims to do "OpenId, Google, OAuth, Twitter, LinkedIn, Yahoo, Readability, Dropbox, Justin.tv, Vimeo, Tumblr, OAuth2, Facebook, GitHub, Instagram, Foursquare, Box.net, LDAP"

Answer 2

Although I haven't tried it yet, I started looking into Pusher for a Node Knockout 2011 entry. In addition to JavaScript, it supports the following non-js clients:

• Objective-C
• ActionScript
• .NET & Silverlight
• Ruby
• Arduino

If messaging via a 3rd party is a possibility, you can try the service for free using their Sandbox plan (20 connections & upto 100K messages/day) and see if it meets your needs. (I'm a little uncertain about the "presence" requirement, though it may be covered in the docs.)