Introduction Welcome to our detailed guide on how to check for open and closed SSH ports. In today's networked world, maintaining secure server connections is critical. Secure Shell (SSH) is a network protocol that provides administrators with a secure way to access a remote computer.  However, ensuring that your SSH ports are configured correctly is essential to prevent unauthorized access and breaches.  This tutorial will provide you with step-by-step instructions on using various tools to determine the status of SSH ports on your system. Whether you're a seasoned system administrator or a novice user, these skills are fundamental to managing and securing your network connections. In this tutorial, How to checks all ports if they are closed or open and if the current ssh version? Using nmap command. Read man nmap page. First, you need to install nmap . For ubuntu $ sudo apt-get install nmap For centos $ sudo yum install nmap For example, checks for open/closed ports