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This is the BSDA Study Guide Book written via a wiki collaboration. This is a work in progress. You may contribute to or discuss this specific page at http://bsdwiki.reedmedia.net/wiki/Determine_which_TCP_or_UDP_ports_are_open_on_a_system.html. Determine which TCP or UDP ports are open on a system Concept Be able to use the utilities found on BSD systems as well as third-party programs to determine which ports are open on a system and which ports are being seen through a firewall. Introduction netstat: show network status services: service name database fstat: identify active files sockstat: list open sockets nmap: network exploration tool and security scanner lsof: list open files Determine which ports are open on a system: Locally: netstat -an sockstat -cl Remotely: nmap hostname or IP Using sockstat: sockstat -cl Examples Practice Exercises More information netstat(1), services(5) and fstat(1); sockstat(1) and third-party nmap and lsof