MQTT

MQTT is the standard lightweight publish/subscribe protocol for machine-to-machine messaging. Endpoint uses the same MQTT client libraries that run on servers and desktops, so your application works against any broker, whether a local Mosquitto instance in the lab, hosted brokers like HiveMQ or EMQX, or the managed brokers inside Azure IoT Hub, AWS IoT Core, and Google Cloud Pub/Sub.

Client

The .NET choice is MQTTnet: full QoS 0 / 1 / 2 support, TLS (using the operating system's certificate trust store), topic filters, and persistent sessions. On Python the standard library is paho-mqtt. On C/C++ use the Eclipse Mosquitto client library that Endpoint firmware already ships.

.NET

using MQTTnet;
using MQTTnet.Client;

var factory = new MqttFactory();
using var client = factory.CreateMqttClient();

var options = new MqttClientOptionsBuilder()
    .WithTcpServer("broker.example.com", 8883)
    .WithTls()
    .WithCredentials("username", "password")
    .WithClientId("endpoint-01")
    .Build();

await client.ConnectAsync(options);
await client.SubscribeAsync("sensors/+/temperature");
await client.PublishStringAsync("sensors/01/temperature", "23.4");

Python

import paho.mqtt.client as mqtt

client = mqtt.Client(client_id="endpoint-01")
client.username_pw_set("username", "password")
client.tls_set()
client.connect("broker.example.com", 8883)
client.subscribe("sensors/+/temperature")
client.publish("sensors/01/temperature", "23.4")
client.loop_forever()

C/C++

// Link with -lmosquitto.
#include <cstdio>
#include <mosquitto.h>

mosquitto_lib_init();
struct mosquitto* client = mosquitto_new("endpoint-01", true, nullptr);

mosquitto_username_pw_set(client, "username", "password");
mosquitto_tls_set(client, nullptr, "/etc/ssl/certs", nullptr, nullptr, nullptr);

mosquitto_connect(client, "broker.example.com", 8883, 60);
mosquitto_subscribe(client, nullptr, "sensors/+/temperature", 0);
mosquitto_publish(client, nullptr, "sensors/01/temperature",
                  4, "23.4", 0, false);

mosquitto_loop_forever(client, -1, 1);
mosquitto_destroy(client);
mosquitto_lib_cleanup();

Running an MQTT broker on the board

Endpoint can host an MQTT broker, not just connect to one. On .NET the MQTTnet package also ships a broker component in the same assembly. On Linux, the Mosquitto broker daemon (mosquitto) is available over the package manager and can be launched from any language. A fleet of local devices can publish to Endpoint, which then forwards aggregated or filtered data upstream to the cloud. See the Endpoint as gateway page for the full pattern.