SSH

Communication Protocols You Should Know Communication protocols are the rules that let devices talk. They define how messages look, how they travel, and how errors are handled. Most networks use layers: the transport layer (TCP or UDP) decides how data moves, while the application layer carries the content (web pages, emails, files). Knowing a few core protocols helps you troubleshoot, build reliable systems, and stay secure. Core protocols at a glance HTTP/HTTPS: Web traffic. Secure HTTPS uses TLS and runs over port 443; plain HTTP uses port 80. DNS: Domain name lookups. Fast and usually UDP, sometimes TCP for large transfers. TCP and UDP: Transport options. TCP is reliable and ordered; UDP is fast and simple, good for real-time apps. TLS/SSL: Encryption for many protocols. It protects data in transit with certificates. SMTP/IMAP/POP3: Email flow. SMTP sends messages; IMAP or POP3 retrieves them, with TLS options. FTP/SFTP/FTPS: File transfer. SFTP and FTPS add encryption. SSH: Secure remote access and file operations. MQTT: Lightweight publish/subscribe for IoT, usually over TCP with TLS in many setups. WebSocket: Real-time, two-way chats and feeds over a persistent TCP connection. How transport shapes talk Two main options exist at the transport layer: TCP and UDP. TCP gives order and reliability, great for web pages, emails, and file transfers. UDP is faster and lighter, used for live streaming or quick status updates where a few lost packets won’t break things. Many modern apps choose TLS to add encryption on top of these transports, making conversations private and authenticated. ...