What packet pattern indicates a closed port?

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Multiple Choice

What packet pattern indicates a closed port?

Explanation:
When a TCP connection is attempted, the first step is a SYN from the client. If the destination port is listening (open), the host replies with a SYN-ACK and the handshake proceeds with the client sending an ACK. If the port is not listening (closed), the host actively rejects the connection by sending a reset (RST), often with an accompanying ACK. This RST response to the initial SYN is what signals a closed port. So a pattern where you see the initial SYN followed by a RST (often shown as RST/ACK) indicates the port is closed. The other patterns correspond to an open port (SYN followed by SYN-ACK) or to segments from an already established connection (ACK only), which don’t indicate a closed port.

When a TCP connection is attempted, the first step is a SYN from the client. If the destination port is listening (open), the host replies with a SYN-ACK and the handshake proceeds with the client sending an ACK. If the port is not listening (closed), the host actively rejects the connection by sending a reset (RST), often with an accompanying ACK. This RST response to the initial SYN is what signals a closed port. So a pattern where you see the initial SYN followed by a RST (often shown as RST/ACK) indicates the port is closed. The other patterns correspond to an open port (SYN followed by SYN-ACK) or to segments from an already established connection (ACK only), which don’t indicate a closed port.

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