Which command is typically used for a quick check of open ports on a server?

The command that is typically used for a quick check of open ports on a server is the one that employs the -F flag. This option runs a fast scan, which means it will scan the most common 100 ports rather than all 65,535 TCP ports. This allows for a quicker assessment of which common services are available on a particular server.

Using -F is particularly useful when the goal is to quickly identify open ports without carrying out the more exhaustive scans, which can take significantly longer. It provides a balance between speed and information by focusing on the most likely ports of interest.

The other command options, while relevant to network scanning and port discovery, are used for different purposes. The -sP is for ping scanning, -sn is similar to a ping scan with no port scan, and -sV goes further by not only scanning for open ports but also attempting to detect service versions running on those ports.