• Server Hardware: A high-performance physical or virtual machine with redundant power supplies, multi-core CPUs, ECC RAM, and high-speed network interfaces running 24/7/365.
• Server Software (Daemon): A background process continuously listening on a specific TCP/UDP port number waiting to service incoming client requests (e.g. Apache listening on Port 80, SSH daemon on Port 22).
| Server Category | Primary Purpose | Protocols Used | Industry Standard Software |
|---|---|---|---|
| Web Server | Serves static content (HTML, CSS, JS, Images), handles SSL/TLS termination, acts as reverse proxy | HTTP, HTTPS | Apache HTTP Server, Nginx, Microsoft IIS, Caddy |
| Application Server | Executes backend business logic, session management, dynamic page compilation, database transactions | HTTP, RMI, RPC | Apache Tomcat, Node.js, Oracle WebLogic, WildFly (JBoss) |
| Database Server | Provides structured data persistence, ACID transactions, complex indexing, relational & NoSQL queries | Proprietary SQL Protocols | MySQL, PostgreSQL, Oracle DB, Microsoft SQL Server, MongoDB |
| Specialized Servers | DNS name translation, Mail routing (SMTP/IMAP), Secure file transfer, Remote CLI shell | DNS, SMTP, POP3, SSH, FTP | BIND (DNS), Postfix / Sendmail (Mail), OpenSSH (Remote shell) |
| Port | Protocol | Transport | Common Service |
|---|---|---|---|
| 20 / 21 | FTP | TCP | File Transfer Protocol (Data/Control) |
| 22 | SSH / SFTP | TCP | Secure Shell remote CLI |
| 23 | Telnet | TCP | Unencrypted remote terminal |
| 25 | SMTP | TCP | Simple Mail Transfer (Email sending) |
| 53 | DNS | UDP / TCP | Domain Name System translation |
| Port | Protocol | Transport | Common Service |
|---|---|---|---|
| 67 / 68 | DHCP | UDP | Dynamic IP allocation |
| 80 | HTTP | TCP | Standard Hypertext Transfer (Plaintext) |
| 110 | POP3 | TCP | Post Office Protocol (Email retrieval) |
| 143 | IMAP | TCP | Internet Message Access Protocol |
| 443 | HTTPS | TCP | HTTP over SSL/TLS (Secure web) |
• Well-Known Ports (0 – 1023): Reserved for standard system services (HTTP, SSH, DNS).
• Registered Ports (1024 – 49151): Assigned to specific vendor applications (e.g. MySQL Port 3306, Tomcat Port 8080).
• Dynamic / Ephemeral Ports (49152 – 65535): Used temporarily by client browsers during outbound sessions.