Knocker is a simple, versatile, and easy-to-use TCP security port scanner written in C, using threads. It is able to analyze hosts and the network services which are running on them. It is available for Linux, FreeBSD, Unix, and Windows95/98/2000.
Gives you the ability to operate Windows using PMCP alone, with its collection of useful utilities. Also includes several network tools. Written in pure C with Win32 API for maximum portability.