Every website load, email, video call, and file upload runs on a small set of internet protocols quietly agreeing on how data should move. Understanding what each one actually does, and where it fits, makes the rest of networking click into place.
Internet protocols are the agreed rules that let a browser in one country and a server in another understand each other perfectly, every single time, without either side ever meeting.
From browsing websites to sending emails and streaming video, countless daily activities depend on internet protocols working correctly in the background. These protocols are what actually ensure data travels efficiently and securely across networks.
This guide covers all seven of the most common internet protocols, HTTP, HTTPS, WebSocket, TCP, UDP, SMTP, and FTP, explaining what each one does, the port numbers and handshakes behind them, and how they differ from each other.
Where Each Protocol Fits: Application vs Transport Layer
Internet protocols split across two main layers of the TCP/IP model. HTTP, HTTPS, WebSocket, SMTP, and FTP all operate at the application layer, defining what the data means. TCP and UDP operate at the transport layer underneath them, defining how that data actually gets moved. Seeing where each of these internet protocols sits in the stack makes the rest of this guide much easier to follow.
| Protocol | Layer | Default Port(s) | Transport Used |
|---|---|---|---|
| HTTP | Application | 80 | TCP |
| HTTPS | Application | 443 | TCP |
| WebSocket | Application | 80 (ws), 443 (wss) | TCP |
| SMTP | Application | 25, 587 (submission) | TCP |
| FTP | Application | 21 (control), 20 (data) | TCP |
| TCP | Transport | N/A, carries other protocols | N/A |
| UDP | Transport | N/A, carries other protocols | N/A |
1. HTTP (Hypertext Transfer Protocol)
HTTP is a foundational protocol for data communication on the World Wide Web. It operates as a simple request response protocol, typically running over TCP.
HTTP defines how clients, like web browsers, send messages to servers and how servers respond. Both request and response headers are in ASCII format, while the message body often follows a MIME like structure.
A typical HTTP request includes a method such as GET, POST, PUT, or DELETE, a target URL, and a set of headers. The server replies with a status code, such as 200 for success, 404 for not found, or 500 for a server error, along with its own headers and the requested content.
This straightforward request and response model was a key factor in the early success of the web, making development and deployment remarkably simple and direct.
2. HTTPS (Hypertext Transfer Protocol Secure)
HTTPS is the secure version of HTTP. It provides a secure channel over an insecure network by adding a layer of encryption and authentication on top of HTTP.
This security is primarily achieved through SSL (Secure Sockets Layer) or its modern successor, TLS (Transport Layer Security). HTTPS operates on a different default port than HTTP, port 443 instead of port 80, and includes an encryption and authentication layer between HTTP and TCP.
Before any HTTP data flows, the client and server perform a TLS handshake: the client sends supported cipher suites, the server responds with its certificate and chosen cipher, and both sides derive a shared session key used to encrypt everything that follows.
This system ensures data integrity and confidentiality, making HTTPS the standard for sensitive communications such as online banking and online retail transactions.
3. WebSocket
WebSocket is an independent protocol built on top of TCP, designed for full duplex communication over a single TCP connection.
It establishes a connection through an HTTP/1.1 101 Switching Protocols handshake. The browser initiates this handshake and the server responds, upgrading the ordinary HTTP connection into a persistent WebSocket connection.
Once established, the WebSocket connection allows for continuous, bidirectional communication between a client and a server without the overhead of repeated HTTP requests. This makes it ideal for real time applications like chat applications, online gaming, and live data feeds, where continuous data exchange is crucial.
4. TCP (Transmission Control Protocol)
TCP is a core protocol of the internet protocol suite, designed to provide reliable, ordered, and error checked delivery of a stream of bytes between applications running on hosts across an unreliable network.
TCP achieves this reliability through sequence numbers, acknowledgments, retransmission of lost packets, and flow control. It is connection oriented, meaning a connection must be established between sender and receiver before any data can be exchanged.
SYN
The client sends a SYN (synchronize) packet to the server, proposing to start a connection and announcing its initial sequence number.
SYN-ACK
The server responds with a SYN ACK packet, acknowledging the client's sequence number and proposing its own.
ACK
The client sends a final ACK packet back, and the connection is now fully established in both directions, ready to carry data.
This three way handshake is what makes TCP suitable for applications where data integrity and guaranteed delivery are paramount, such as web browsing over HTTP and HTTPS, email over SMTP, and file transfers over FTP.
5. UDP (User Datagram Protocol)
UDP is a connectionless, unreliable, datagram based transport protocol. Unlike TCP, UDP prioritizes speed and efficiency over reliability.
It does not establish a connection before sending data, and it does not guarantee delivery, order, or error checking of packets. There is no handshake, no acknowledgment, and no retransmission of lost data.
TCP is a phone call where both sides confirm every sentence was heard. UDP is a radio broadcast, sent once, with no confirmation anyone caught it. Which one you want depends entirely on whether a missed word matters more than a delayed one.
This tradeoff makes UDP suitable for applications where real time performance is critical and occasional data loss is acceptable, such as streaming video, online gaming, and Voice over IP (VoIP).
TCP
Connection oriented, reliable, ordered delivery with retransmission. Slower due to overhead, but nothing gets lost silently.
UDP
Connectionless, no delivery guarantee, no retransmission. Faster and lighter, but packets can arrive out of order or not at all.
6. SMTP (Simple Mail Transfer Protocol)
SMTP is the standard protocol used for sending email messages between servers. It defines the format and transmission method for emails during the sending process.
When an email is sent, the email client typically hands it to an SMTP server, which then relays it onward to the recipient's SMTP server, commonly using port 25 between servers or port 587 for client submission with authentication.
SMTP is primarily a push protocol, meaning it is used only for sending mail. Retrieving mail from a mailbox is handled by separate protocols, POP3 or IMAP, rather than SMTP itself.
7. FTP (File Transfer Protocol)
FTP is a standard network protocol used for transferring computer files between a client and server on a network. It operates at the application layer, running over TCP for reliable, connection oriented data transfer.
FTP actually uses two separate channels: a control channel, typically port 21, for commands and responses, and a data channel, typically port 20, for the actual file transfer itself.
Before a client and server exchange files, they establish a connection through a three way handshake, the same underlying TCP mechanism covered earlier, guaranteeing a reliable connection. FTP is widely used for uploading and downloading files, maintaining websites, and transferring large datasets.
Watch: Every Network Protocol Simply Explained
This video breaks down HTTP, HTTPS, TCP, UDP, SMTP, and FTP alongside DNS and DHCP, useful for seeing how these internet protocols fit together in practice.
Video: "Every Network Protocol Simply Explained", via YouTube.
FAQs on Internet Protocols
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Read Full Article →External References
These are the official IETF standards documents defining the protocols covered in this guide.
- RFC 9110, HTTP Semantics, IETF
- RFC 9293, Transmission Control Protocol (TCP), IETF
- RFC 6455, The WebSocket Protocol, IETF
What we learn today
- HTTP handles the basic request and response model of the web, while HTTPS adds TLS encryption on top of it for secure communication.
- WebSocket upgrades an HTTP connection into a persistent, bidirectional channel for real time applications.
- TCP guarantees reliable, ordered delivery through a three way handshake, while UDP trades that reliability for speed.
- SMTP only pushes email outward, while FTP splits file transfer into separate control and data channels.
- Nearly every one of these internet protocols ultimately depends on TCP underneath it to actually move the bytes reliably.