Hands-On Penetration Testing with Kali NetHunter

Full Open/TCP connect scans

Of all the scans, the full open scan is very easy to visualize and understand, as we have kind of already seen it. A full open scan establishes a TCP three-Way handshake prior to performing any port scans on the target system, with the goal of determining their status if they are open and closed.

This type of scan is able to quickly determine whether a port is open or closed  because it establishes a TCP three-way handshake with the target.

When the initiate no longer wants to communicate with the target, the initiate will send a TCP FIN packet to let the target know it would like to gracefully end the session:

Close and Open Port responses

If a port is open on a target device, the target responds with an ACK ...