Since Server2012 task manager become hard to use and details are hided. There are two suggested tools for troubleshooting.
Two useful tools for troubleshooting, using tcpview to find out which program using your port or mass sending. Then use process explorer to find process and dll loaded.
https://docs.microsoft.com/en-us/sysinternals/downloads/tcpview
https://docs.microsoft.com/en-us/sysinternals/downloads/process-explorer
Keep running those two tools may cause CPU high usage, better close it when job is done.