Lsof is a Unix-specific diagnostic tool. Its name stands for LiSt Open Files, and it does just that. It lists information about any files that are open by processes currently running on the system. It is the single most powerful utility for inspecting running processes and determining which process is listening to which ports.
You can download it from the following link: https://packetstormsecurity.com/files/download/10521/lsof_4.48_W.tar.gz
Source: https://packetstormsecurity.com/files/10521/lsof_4.48_W.tar.gz.html