Monitoring open ports is an important part of Linux server security and management. Open ports indicate which services are listening for network connections. Knowing your open ports helps prevent illegal access, troubleshoot network issues, and secure your server.<\/p>\n
In this guide, we will cover how to check open ports on Ubuntu, CentOS, and Debian using various methods, along with best practices to manage them efficiently.<\/p>\n
ss is a modern replacement for netstat and provides detailed info about TCP, UDP, and listening ports.<\/p>\n
ss -tuln<\/pre>\n<\/li>\n
Netid State\u00a0\u00a0\u00a0\u00a0\u00a0 Recv-Q Send-Q Local Address:Port\u00a0 Peer Address:Port\r\ntcp\u00a0\u00a0\u00a0 LISTEN\u00a0\u00a0\u00a0\u00a0 0\u00a0\u00a0\u00a0\u00a0\u00a0 128 0.0.0.0:22\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 0.0.0:*\r\ntcp\u00a0\u00a0\u00a0 LISTEN\u00a0\u00a0\u00a0\u00a0 0\u00a0\u00a0\u00a0\u00a0\u00a0 100 127.0.0.1:3306\u00a0\u00a0\u00a0\u00a0\u00a0 0.0.0.0:*<\/pre>\n<\/li>\n<\/ol>\nUsing the netstat Command
\n<\/strong><\/h3>\nnetstat is widely used, but may require installation on newer systems.<\/p>\n
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- Install net-tools if not available:
\n# Ubuntu\/Debian<\/p>\nsudo apt update\r\nsudo apt install net-tools<\/pre>\n# CentOS\/RHEL<\/p>\n
sudo yum install net-tools<\/pre>\n<\/li>\n- <\/a>Check open ports:\n
netstat -tuln<\/pre>\n<\/li>\n- Options:
\n-t >TCP
\n-u> UDP
\n-l > Listening
\n-n> Show numeric ports<\/li>\n<\/ol>\nUsing the lsof Command
\n<\/strong><\/h3>\nlsof lists open files and network connections.<\/p>\n
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- Command to list listening ports:\n
sudo lsof -i -P -n | grep LISTEN<\/pre>\n<\/li>\n- <\/a>Explanation:
\n-i > network files
\n-P > shows port numbers
\n-n > numeric addresses<\/li>\n<\/ol>\nUsing the nmap Command (Network Scanner)
\n<\/strong><\/h3>\nnmap can scan local or remote servers for open ports.<\/p>\n
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- Install nmap:
\n# Ubuntu\/Debian<\/p>\nsudo apt install nmap<\/pre>\n# CentOS\/RHEL<\/p>\n
sudo yum install nmap<\/pre>\n<\/li>\n- Scan local machine:\n
sudo nmap -sT -O localhost<\/pre>\n<\/li>\n- Scan a remote<\/a> server:\n
sudo nmap -sT example.com<\/pre>\nTip:<\/strong> nmap provides a detailed report with port numbers, protocols, and running services.<\/li>\n<\/ol>\n
Best Practices After Checking Open Ports<\/strong><\/h3>\n
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- Close Unused Ports: Stop unnecessary services and use firewall rules (ufw for Ubuntu\/Debian, firewalld for CentOS).<\/li>\n
- Regular Monitoring: Schedule periodic port checks to <\/a>detect unusual activity.<\/li>\n
- Secure Critical Ports: For SSH, change the default port or enable key-based authentication.<\/li>\n<\/ol>\n
Conclusion:<\/strong><\/h3>\n
In this way, we can check open ports on our Linux server (Ubuntu, CentOS, Debian)<\/strong>, which is essential for security and efficient server management.<\/p>\n
By combining this with proper firewall configuration and regular monitoring<\/strong>, we can keep our server secure and reliable. If you run into any difficulty, feel free to contact our support staff at any time.<\/p>\n
\nMonitoring active ports on your server?<\/strong>
\nFor complete control over services and networking, consider using a Linux VPS with full system access<\/a>.\n<\/div>\n