Everything can be a server/client!by Rob Galanakis on 30/01/2012
We Tech Artists can get intimidated when talking about servers and clients. They remind us of a world of frameworks and protocols we’re not familiar with, run by hardcore server programmers who seem to have a very demanding job. Fortunately, that needn’t be the case, and understanding how to turn anything into a server/client can open limitless possibilities.
You can think of server/client as a way to get two processes to communicate to each other using sockets, that is more flexible than other means of IPC such as COM or .NET marshalling. Your server can be local, or it can be remote, and very little usually has to change. Moreover, you can define much more flexible protocols/mechanisms, so you can communicate across literally any programming language or platform.
The practical reason everything can be a server/client is because we don’t have to understand much of how anything works under the hood. You follow some examples of how to set up a server and client using the framework of your choice (I’m a huge, huge fan of ZeroMQ which has bindings for pretty much everything including python and the CLR). Once you get comfortable, you just design your interface, and implement one on the server and on the client (the client just usually sends data over to the server and returns the response). Actually I really like how WCF recommends you build your server and client types, even though I am not a big fan of the framework. And I do the same for Python even though it’s not strictly necessary ;)
So your server just needs to poll for messages in a loop, and the client sends requests to it, and the server sends back replies. So driving one app with another is as simple as creating a server on the slave and polling in a (usually non-blocking) loop, and having the client send commands to it. You can invert the relationship on a different port and now you have bi-directional communication (hello live-updating in your engine and DCC!).
The real power of this, I’ve found, is that I really have full control over how I want things to work. No more going through shitty COM or .NET interop, no more Windows messaging. I define the interface that declares what functionality I need, and can implement it in a sensible and native way (ie, not COM, etc.).
For example, we use this for:
- Recreating a Maya scene in our editor, and interactively updating our editing scene by manipulating things in Maya, even though their scene graphs and everything else are nothing alike.
- Running a headless version of our editor, so we can interact with libraries that only work inside the editor/engine, from any other exe (like regular python, Maya, or MotionBuilder).
- Having a local server that caches and fetches asset management information, so data between tools is kept in sync for the entire machine and there are no discrepancies per-app.
If we had a need, we could easily extend this so any other programs could talk to each other. In fact this is generally how it’s done when apps talk to each other: I’m not presenting anything new, just trying to convince you it becomes really really easy.
If you’re anything like me, thinking about things in a server/client scenario can give you an entirely new perspective on how you develop tools and firstname.lastname@example.org