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Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

client ID

The name a client gives the broker so the broker can tell connections apart and find its saved session.

The client ID identifies a connection to the broker; two clients using the same ID knock each other off, and a persistent session is looked up by it.

Examples

  • The ESP32 sketch builds its client ID from its MAC address, such as gh- followed by twelve hex digits, so it is unique.

  • mosquitto_sub makes up a random client ID unless you give one with -i.

See also

client Mosquitto MAC address broker
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