Error starting userland proxy: Bind for 0.0.0.0:2181: unexpected error Permission denied
I ran across this same issue after having used Zookeeper on port 2181 for months. I couldn't figure out why it wouldn't bind to port 2181 as I had ran netstat -aon | findstr '2181' as admin and would get back no results. I eventually came to the conclusion that the port was in fact in use by some process even though it wasn't listed. The solution that I found to still use port 2181 (this was critical for my application):
Start Windows in Safe Mode with Networking
In powershell/cmd run the command netsh int ipv4 add excludedportrange protocol=tcp startport=2181 numberofports=1 This will reserve the port 2181 so when you boot back into normal windows mode no application will steal the port before you can use it.
Boot into regular windows and start Zookeeper. With this there will be no bind issues!