I've been wondering about private server design. These games mostly use UDP, right? So does that mean the server has to be written in Java or C++? Also does the

I've been wondering about private server design. These games mostly use UDP, right? So does that mean the server has to be written in Java or C++? Also does the server need to be very fast, again requiring near-native performance with Java? Seems like inventory management and chat could be simple HTTP API calls, but player movement is a whole different level of complexity.