Communication Protocols

Every time your phone loads a page, your ESP32 sends a sensor reading, or a smartwatch talks to an app, two machines are following a shared set of rules about who speaks first, how the message is shaped, and what to do when something gets lost. That set of rules is a communication protocol. This track explains the protocols you meet most often as a web, mobile or IoT developer, one at a time, with diagrams of what actually travels over the wire.

The Big Picture

Protocols are stacked in layers. The lower layers move bits and packets from one device to another; the layers above them decide what the bytes mean. Most of the protocols in this track sit on top of TCP, and one of them (Bluetooth LE) has a small stack of its own.

How the protocols in this track fit together Two stacks. The internet stack has HTTP, WebSocket and MQTT on top, an optional TLS layer, TCP and UDP below, then IP and the Wi-Fi or Ethernet link. The Bluetooth LE stack has GATT and ATT, then L2CAP and the link layer, then the 2.4 GHz radio. The internet stack Bluetooth LE stack HTTP / HTTPS WebSocket MQTT TLS (optional): encrypts the layer above TCP: reliable, ordered UDP: fast IP: addresses and routing Wi-Fi or Ethernet GATT and ATT services and characteristics L2CAP and Link Layer packets, connections, channels 2.4 GHz radio the physical layer No TCP or IP here: BLE has its own small stack
The five lessons of this track on one page: three application protocols on TCP, the TCP and UDP choice underneath them, and Bluetooth LE on its own stack.

What You'll Learn In This Track

LessonWhat it answers
TCP vs UDPHow data is delivered: the three-way handshake, retransmission, and when giving up reliability is the right call
HTTP & HTTPSWhat a request and a response look like, status codes, and what the TLS handshake and certificates add
WebSocketHow a normal HTTP request turns into a two-way connection for chat, live dashboards and games
MQTTPublish and subscribe through a broker, topics, QoS levels, and why IoT devices like it
Bluetooth Low Energy (BLE)Advertising, connections, and the GATT model of services and characteristics
Suggested order: start with TCP vs UDP, because HTTP, WebSocket and MQTT all build on it. BLE does not depend on the others, so you can read it at any time.

Where This Meets the Rest of the Site

More Protocols Are Coming

The track will keep growing. Planned next:

CoAPDNSFTP & SFTPSMTPZigbeeLoRa & LoRaWANUARTI2CSPIRS-485 & ModbusCAN bus

Next steps: Head to TCP vs UDP to see how data is really delivered between two machines.