Application Protocols: HTTP, HTTPS, SSH, FTP
TCP and UDP handle getting data between devices reliably (or quickly). But they don't define what that data means. That's the job of application protocols — they establish the rules for how programs actually communicate.
Think of it like languages. TCP/UDP are like the postal service delivering letters. Application protocols are the languages written in those letters — English, Spanish, formal business correspondence, casual notes.
HTTP and HTTPS: The Web's Language
HTTP (Hypertext Transfer Protocol) is how web browsers and servers communicate. When you visit a website, your browser sends an HTTP request, and the server sends back an HTTP response containing the webpage.
HTTPS is HTTP with encryption. The "S" stands for "Secure." All the same communication happens, but it's encrypted so others can't read it in transit. Modern websites use HTTPS by default — you'll see a padlock icon in your browser's address bar.
HTTP and HTTPS typically use ports 80 and 443, respectively.
SSH: Secure Remote Access
SSH (Secure Shell) lets you securely connect to and control remote computers via command line. System administrators use SSH to manage servers, developers use it to deploy code, and it's essential for working with cloud infrastructure.
SSH encrypts everything — your commands, the responses, even your password (or key) during login. It typically uses port 22.
FTP and SFTP: File Transfer
FTP (File Transfer Protocol) was designed for transferring files between computers. However, traditional FTP sends data unencrypted, making it insecure for sensitive files.
SFTP (SSH File Transfer Protocol) provides the same file transfer capability but over an encrypted SSH connection. Most modern file transfers use SFTP or other secure alternatives.
Why Protocols Matter
Understanding these protocols helps you:
- Know what's happening when you browse the web
- Recognize security implications (HTTP vs HTTPS)
- Work with servers and remote systems
- Troubleshoot connection problems