Some things should be printed immediately

[lazyatom]

If you were using a printer to send a message, you might want it to appear without intervention by the recipient.

I think we might be able to do this elegantly using HTTP headers (e.g. X-Print: now).

[lazyatom]

We might be able to re-use the header processing from here: https://github.com/ovidiucp/TinyWebServer/blob/master/TinyWebServer.cpp#L99

(Or at least use the technique of storing the headers in some intermediate structure, rather than having to parse them as they arrive in the stream).

[lazyatom]

We might also be able to use a different status code, which could be easier to parse than a proper HTTP header...

[lazyatom]

I've been thinking a bit more about this. I'm relatively sure that there's no way to fit in decent header processing into the space we have left on the Ardunio, principally because the headers could arrive in any order from the server.

However, the server could supply a single, custom header that included a more easily parseable set of values. For example:

HTTP/1.1 200 OK
Date: Fri, 08 Mar 2013 21:13:04 GMT
Status: 200 OK
Content-Type: vnd.gofreerange.printer.A2-raw
Content-length: 32045
X-Printer-PrintImmediately: true
X-Printer-Encoded-Status: 200|32045|1

The server returns the interesting headers as normal, but also provides a single, encoded header which has a value that can be more easily broken down: 200 is the status code, 32045 is the content length and 1 is a flag indicating whether or not to print immediately.

Using a single header makes the Arduino software much simpler.