I use Python myself. I don't think the language matters that much, each has its pros and cons. Python is nice because it's fast to write and the standard library has helpful things like encryption and a thread pool built in. Some might prefer a more strongly typed language (e.g. C++) as the compiler can catch bugs for you before you run your program. C++ might also be best from a performance perspective, then again your main concern is network latency, so I don't think the language matters there.

Bottom line, pick whatever you like.