Not necessarily an "off-the-shelf" solution, but something worth considering if you are designing some application over HTTP: AWS (Ada Web Server, nothing to do with Amazon... only an unfortunate acronym clash), it is a library (written in Ada) implementing an HTTP server that can be used to implement from a simple "page serving" server to complex HTTP application.
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OK, yet another UAV project, but a bit peculiar....
AdaPilot (http://adapilot.likeabird.eu/) is an open source project aimed to make a DO-178 certifiable (https://en.wikipedia.org/wiki/DO-178B) control software for remotely piloted vehicles that is safety critical, powerful and flexible but also easy to extend. Development is done in Ada and SPARK, a subset of Ada suitable for formal checking (https://en.wikipedia.org/wiki/SPARK_%28programming_language%29).
If you never used Ada or think it is too old, it is a nice occasion to be exposed to it... (and fall in love with it :-) )
Not necessarily an "off-the-shelf" solution, but something worth considering if you are designing some application over HTTP: AWS (Ada Web Server, nothing to do with Amazon... only an unfortunate acronym clash), it is a library (written in Ada) implementing an HTTP server that can be used to implement from a simple "page serving" server to complex HTTP application.
See http://libre.adacore.com/tools/aws/