• Network ports are virtual points where network connections start and end. They serve as logical access points for the transmission and reception of data between devices. Imagine that the network ports as channels on a television; each channel broadcasts a different stream of information, similarly, each port is associated with specific types of network services and protocols.
• Each port is identified by a unique number, ranging from 0 to 65535, known as the port number. This numerical value is crucial as it distinguishes one type of network service from another, enabling computers to manage multiple simultaneous connections effectively.

Types of Network Ports                   

Well-Known Ports (0-1023): 

These ports are reserved for common services and protocols such as HTTP (Port 80), HTTPS (Port 443), FTP (Port 21), and SSH (Port 22). They are widely recognized and standardized, ensuring consistent communication across different devices and networks.

• Port 20, 21: FTP (File Transfer Protocol)
• Port 22: SSH (Secure Shell)
• Port 23: Telnet
• Port 25: SMTP (Simple Mail Transfer Protocol)
• Port 53: DNS (Domain Name System)
• Port 67, 68: DHCP (Dynamic Host Configuration Protocol)
• Port 80: HTTP (HyperText Transfer Protocol)
• Port 110: POP3 (Post Office Protocol version 3)
• Port 119: NNTP (Network News Transfer Protocol)
• Port 123: NTP (Network Time Protocol)
• Port 143: IMAP (Internet Message Access Protocol)
• Port 161, 162: SNMP (Simple Network Management Protocol)
• Port 194: IRC (Internet Relay Chat)
• Port 443: HTTPS (HTTP Secure)
• Port 445: Microsoft-DS (Active Directory, Windows shares)
• Port 465: SMTPS (SMTP Secure)
• Port 514: Syslog
• Port 636: LDAPS (LDAP over SSL)
• Port 993: IMAPS (IMAP Secure)
• Port 995: POP3S (POP3 Secure)

Registered Ports (1024-49151): 

These ports are assigned by the Internet Assigned Numbers Authority (IANA) for specific applications and processes that are not as universally used as the well-known ports but still require standardized port numbers. Examples include Microsoft SQL Server (Port 1433) and MySQL (Port 3306).

• Port 1433: Microsoft SQL Server
• Port 1521: Oracle Database
• Port 1723: PPTP (Point-to-Point Tunneling Protocol)
• Port 3306: MySQL Database
• Port 3389: RDP (Remote Desktop Protocol)
• Port 5432: PostgreSQL Database
• Port 5900: VNC (Virtual Network Computing)
• Port 5984: CouchDB
• Port 6379: Redis
• Port 8000: Common alternative HTTP port
• Port 8080: HTTP Alternate (commonly used for proxy and web servers)
• Port 8443: HTTPS Alternate

Dynamic or Private Ports (49152-65535): 

Also known as ephemeral ports, these are used for temporary or private communications. They are not assigned by IANA and can be utilized by any application or process for short-term purposes. These ports are typically used for client-side communications where the port number is chosen dynamically by the operating system.

• Port 49152-65535

Common Uses of Network Ports     

Web Browsing: 

• When you access a website, your browser uses port 80 for HTTP or port 443 for HTTPS to request and receive data from web servers.

Email Services: 

• Email protocols like SMTP (Port 25), IMAP (Port 143), and POP3 (Port 110) use specific ports to send and retrieve emails.

Remote Access: 

• Protocols such as SSH (Port 22) and RDP (Port 3389) allow users to remotely access and control other computers securely.

File Transfers: 

• FTP (Port 21) and SFTP (Port 22) enable the transfer of files between devices over a network.

Importance of Network Ports in Security

• Network ports play a critical role in network security. Since each port can potentially serve as an entry point for unauthorized access or malicious attacks, managing and securing these ports is vital. 
• Firewalls, for instance, use port numbers to filter traffic, allowing or blocking data packets based on security rules. Understanding which ports need to be open and which should be closed is a fundamental aspect of network security management.
• Intrusion detection systems (IDS) and intrusion prevention systems (IPS) also monitor port activity to detect and mitigate threats. By analyzing the traffic flowing through different ports, these systems can identify suspicious activities and respond accordingly to protect the network.

Importance and Usage

• Understanding these port numbers is crucial for network management and security. Network administrators and security professionals often configure firewalls and intrusion detection systems to monitor traffic on specific ports, blocking unwanted or malicious activities while allowing legitimate communications.
• Properly configuring and securing these ports ensures that critical services remain accessible and protected from unauthorized access. For example, closing unused well-known ports and monitoring registered ports can help prevent common exploits and attacks.