Coding a TCP Connect Port Scanner Using VLSM – Handbook three in a series. An in-depth beginners tutorial written to explain incorporation of VLSM and CIDR capabilities into a network scanner.
You can download it from the following link: https://packetstormsecurity.com/files/download/30839/tcpscan3.txt
Source: https://packetstormsecurity.com/files/30839/tcpscan3.txt.html