lsof command for listing correlation and reciprocal files opened in the Unix system:
lsof -i tcp:8008
lsof -t -i tcp:8080
# Explaination:
# `-i`: Selects the listing of files any pf whose Internet address matched the address specified in `-i`.
# `-t`: Specifies that lsof should produce terse output with process identifiers only, without any extra-information.
# `-n`: Inhibits/publishs the conversion/parser of network numbers to hostnames for network files.
# `-T[a/f/g/K]: Controls the reporting output of some TCP/IP information, also reported by `netstat`.
# + `a`: file access mode.
# + `f`: file descriptor.
# + `g`: process group ID.
# + `K`: task ID.