Bandwhich is a free and open source command-line bandwidth utilization for Linux and MacOS. Using this tool you can get the real time bandwidth utilization of your current network by your system process, connection and remote IP/hostname. It is a good network monitor tool. It is released under open source MIT License. You can easily find what is taking up your bandwidth in your computer system. Its working principle is simple, First it sniffs the current network interface and records IP packet size and after that it cross referencing it with the /proc filesystem on linux or lsof on macOS.