Who is using a port

More lsof commands

• List all network connections
  lsof -i -n -Pcopy

  Show all open network connections without DNS resolution

• Find open files on a filesystem
  lsof +D /var/logcopy

  Show all processes with open files under /var/log

• Find deleted files still held open
  lsof | grep '(deleted)'copy

  Find files deleted but still held open by processes (disk bloat)

• ss: show listening sockets
  ss -tlnpcopy

  Show TCP listening ports with process names

• ss: show all TCP connections
  ss -tanp | grep ESTABcopy

  Filter established TCP connections with process info

all 19 lsof commands →