The difference between daemons and agents is that daemons run as root and are intended to run in the background.
Agents are run with the privileges of a user and may run the foreground.

stack a place in physical memory where a running program process stores local variables

netstat is used to display network connections, routing tables and a whole bunch of network and interface stats.

When a function is called, it’s arguments are pushed onto the stack.

To monitor which files an application is accessing

fs_usage

netstat a program creates a socket, binds a port, then listens for a connection.

To display a list of active TCP or UDP connections

netstat -n -A inet -t
netstat -n -A inet -u

To find out all the ports being used by a single application or process using the PID

netstat -A inet -n -p | grep PID