ncat

Ncat is a networking utility from the Nmap Project that reads and writes data across network connections. Built as a modern, more secure replacement for the classic netcat, Ncat provides a flexible tool for debugging, testing, and tunneling networks. It is cross-platform and packaged with the Nmap suite, available on Windows and Unix-like systems.

Operational modes include client mode (connecting to a remote host) and server mode (listening for incoming connections). Ncat can use both TCP and UDP transport, supports IPv4 and IPv6, and can function as a simple data relay, proxy, or gateway between connections. It also offers encrypted communication via SSL/TLS and can verify peer certificates, making it suitable for secure, authenticated connections. In addition to basic data piping, Ncat can invoke external programs or interact with local shells in certain configurations, enabling flexible pipelines and automation.

Because of its scripting-friendly interface, Ncat is commonly used in network diagnostics, penetration testing, and remote administration. It integrates with other Nmap tools and follows a philosophy of compatibility with traditional netcat syntax while extending functionality with modern features and robust error handling.

See also: Netcat; Nmap; TCP/IP utilities.