twisted python request/response message and substantial binary data transfer

I am trying to implement a server using python-twisted with potential C# and ObjC clients. I started with LineReceiver and that works well for basic messaging, but I can't figure out the best approach for something more robust. Any ideas for a simple solution for the following requirements?

• Request and response
  • ex. send message to get a status, receive status back
• Recieve binary data transfer (non-trivial, but not massive - less than a few megs)
  • ex. bytes of a small png file

AMP seems like a feasible solution for the first scenario, but may not be able to handle the size for the data transfer scenario.

I've also looked at full blown SOAP but haven't found a decent enough example to get me going.

I like AMP a lot. twisted.protocols.amp is moderately featureful and relatively easily testable (although documentation on how to test applications written with it is a little lacking).

The command/response abstraction AMP provides is comfortable and familiar (after all, we live in a world where HTTP won). AMP avoids the trap of excessive complexity (seemingly for the sake of complexity) that SOAP fell squarely into. But it's not so simple you won't be able to do the job with it (like LineReceiver most likely is).

There are intermediate steps - for example, twisted.protocols.basic.Int32Receiver gives you a more sophisticated framing mechanism (32 bit length prefixes instead of magic-bytes-terminated-lines) - but in my opinion AMP is a really good first choice for a protocol. You may find you want to switch to something else later (one size really does not fit all) but AMP is at the sweet spot between features and simplicity that seems like a good fit for a very broad range of applications.

It's true that there are some built-in length limits in AMP. This is a long standing sore spot that is just waiting for someone with a real-world need to address it. :) There is a fairly well thought-out design for lifting this limit (without breaking protocol compatibility!). If AMP seems otherwise appealing to you then I encourage you to engage the Twisted development community to find out how you can help make this a reality. ;)

There's also always the option of using AMP for messaging and to set up another channel (eg, HTTP) for transferring your larger chunks of data.