Networking

Kog apps talk to the network with the same globals you already know from the web — fetch, WebSocket, WiFi, and a Kog-native socket API — available with no import:

const res = await fetch('https://api.example.com/status');
const status = await res.json();

No import { fetch }, no setup. The runtime installs these globals before your app runs, on every target: the ESP32 device, the desktop simulator, and the in-browser playground.

One surface, three targets

The API is identical everywhere; only what's underneath changes.

	ESP32 device	Desktop simulator	Web playground
fetch / WebSocket	native HTTP/WS client	host sockets	the browser's own (CORS applies)
TCPSocket / UDPSocket / TCPServer	lwIP	host sockets	not available — throws a clear error
WiFi	real join	always-connected emulation	always-connected emulation

This means you can prototype a fetch-driven dashboard in the playground, run it in the simulator, and flash it to a board — no code changes.

Honest about the edges

Kog is a microcontroller runtime, not a browser, so the surface is narrowed to what native actually delivers. The narrowings are deliberate and documented: bodies are buffered (no ReadableStream), there's no Blob/FormData, sockets deliver ArrayBuffer, and Wi-Fi is emulated off-device. The full list is in the API reference divergences.

Two edges worth knowing up front:

• CORS is real in the web playground. There, fetch and WebSocket are the browser's, so cross-origin calls obey the same-origin policy. On a device there is no CORS. See the fetch guide.
• Raw sockets don't exist in a browser. TCPSocket/UDPSocket/TCPServer throw a helpful error in the playground; run them on a device or the desktop simulator.

Where to go next

• fetch — HTTP requests, JSON, timeouts, errors, CORS.
• WebSocket — live bidirectional streams.
• Sockets — raw TCP/UDP and running a server on-device.
• Wi-Fi — connecting, and baking credentials in at flash time.
• API reference — every global, every method, every divergence.