TCP Half Open Scan

A TCP Half Open Scan determines if a port is open by performing the first half of a three-way handshake. It is also referred as the SYN scanning. In SYN scanning, the hostile client or attacker attempts to set up a TCP/IP connection with a server at every possible port. This is done by sending a SYN (synchronization) packet, as if to initiate a three-way handshake, to every port on the server