I started using NanoHTTPD for a project. Indeed it is very good in its simplicity. Unfortunately it turned out that I need to handle simultaneous connections, for example I have a very long response and in the meanwhile the server shall not be blocked.
What do you recommend? I need it to be simple and feature rich as Nano.
NanoHttpd processes incoming requests with a simple 1-request/1-thread multi-threading model, and it's also multi-instance friendly so you can spin up multiple instance of the server to handle connections on different ports if you need to.