Network port scanners
Masscan (high-performance port scanner)
Masscan is a security tool to perform a network scan for many systems at once. It is optimized asynchronous transmissions to achieve its performance.
Nmap (network and vulnerability scanner)
Nmap is a security scanner that can perform a port scan, network exploration, and determine vulnerabilities
portSpider (network vulnerability scanner)
portSpider is a security tool to scan network ranges and find open ports. The goal of the tool is to find vulnerable services.
QuickScan (port scanning utility)
QuickScan is a simple port scanning utility with additional abilities like resolving. It has a built-in WHOIS lookups, among other supporting features.