Familiarize yourself with your ports.

Network ports are endpoints for communication in networking. They help direct data packets to the correct application or service on a device. Ports are identified by numbers, ranging from 0 to 65535.

Well-Known Ports (0-1023): Reserved for widely-used services and protocols, like HTTP (port 80) or FTP (port 21).

Registered Ports (1024-49151): Used by applications that are not as universally recognized but still need to be identified uniquely.

Dynamic/Private Ports (49152-65535): Typically used for temporary or private communications, often assigned dynamically by the operating system.

Ports work with IP addresses to ensure that data is routed to the correct service on a server or client machine.

These ports are assigned and managed by the Internet Assigned Numbers Authority (IANA). Here’s a detailed look at some commonly used well-known ports:

Port 20 (FTP Data): Used for data transfer in the File Transfer Protocol (FTP). It is used alongside port 21.

Port 21 (FTP Control): Used for sending commands and receiving responses in FTP. It establishes and controls the connection.

Port 22 (SSH): Used for Secure Shell (SSH) protocol, which provides secure remote login and command execution. It also supports SCP (Secure Copy Protocol) and SFTP (SSH File Transfer Protocol).

Port 23 (Telnet): Used for the Telnet protocol, which allows for remote command-line interface access. It is less secure than SSH and is largely considered outdated.

Port 25 (SMTP): Used for Simple Mail Transfer Protocol (SMTP), which is responsible for sending emails between servers.

Port 53 (DNS): Used for Domain Name System (DNS) services, which translate domain names into IP addresses and vice versa.

Port 67 (DHCP Server): Used by the Dynamic Host Configuration Protocol (DHCP) server to assign IP addresses to devices on a network.

Port 68 (DHCP Client): Used by the DHCP client to receive IP address assignments from the DHCP server.

Port 80 (HTTP): Used for Hypertext Transfer Protocol (HTTP), which is the foundation of data communication for the World Wide Web.

Port 110 (POP3): Used for Post Office Protocol version 3 (POP3), which allows email clients to retrieve emails from a server.

Port 143 (IMAP): Used for Internet Message Access Protocol (IMAP), which allows email clients to access and manage emails on a server.

Port 443 (HTTPS): Used for Hypertext Transfer Protocol Secure (HTTPS), which is the secure version of HTTP, providing encrypted communication over the web.

Port 3389 (RDP): Used for Remote Desktop Protocol (RDP), which allows users to remotely access and control a Windows desktop or server.

Port 587 (SMTP with STARTTLS): Used for sending emails securely with STARTTLS encryption, an extension of SMTP.

These well-known ports ensure that standard services and protocols can communicate effectively across the internet and within networks. They are fundamental to many internet and network operations.