MacOS stuff

To list open files (process id’s and ports, actually):

sudo lsof -i -P
   
To avoid text wrapping, pull the right edge to expand the screen width.

The right-most column heading "Name" shows the port (either TCP or UDP).

To filter a particular port number:

sudo lsof -i -P | grep 8080
   
The second column, PID, lists the process identifier. Copy a number for use in the kill command:

sudo kill 289
   

.dmg (Disk Image) files can be mounted from the command line:

hdiutil attach /path/to/diskimage.dmg