OVMS3-idf/examples/protocols/mqtt/tcp/README.md

# ESP-MQTT sample application
(See the README.md file in the upper level 'examples' directory for more information about examples.)

This example connects to the broker URI selected using `make menuconfig` (using mqtt tcp transport) and as a demonstration subscribes/unsubscribes and send a message on certain topic.
(Please note that the public broker is maintained by the community so may not be always available, for details please see this [disclaimer](https://iot.eclipse.org/getting-started/#sandboxes))

Note: If the URI equals `FROM_STDIN` then the broker address is read from stdin upon application startup (used for testing)

It uses ESP-MQTT library which implements mqtt client to connect to mqtt broker.

## How to use example

### Hardware Required

This example can be executed on any ESP32 board, the only required interface is WiFi and connection to internet.

### Configure the project

* Open the project configuration menu (`idf.py menuconfig`)
* Configure Wi-Fi or Ethernet under "Example Connection Configuration" menu. See "Establishing Wi-Fi or Ethernet Connection" section in [examples/protocols/README.md](../../README.md) for more details.
* When using Make build system, set `Default serial port` under `Serial flasher config`.

### Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

```
make -j4 flash monitor
```

(To exit the serial monitor, type ``Ctrl-]``.)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

## Example Output

```
I (3714) event: sta ip: 192.168.0.139, mask: 255.255.255.0, gw: 192.168.0.2
I (3714) system_api: Base MAC address is not set, read default base MAC address from BLK0 of EFUSE
I (3964) MQTT_CLIENT: Sending MQTT CONNECT message, type: 1, id: 0000
I (4164) MQTT_EXAMPLE: MQTT_EVENT_CONNECTED
I (4174) MQTT_EXAMPLE: sent publish successful, msg_id=41464
I (4174) MQTT_EXAMPLE: sent subscribe successful, msg_id=17886
I (4174) MQTT_EXAMPLE: sent subscribe successful, msg_id=42970
I (4184) MQTT_EXAMPLE: sent unsubscribe successful, msg_id=50241
I (4314) MQTT_EXAMPLE: MQTT_EVENT_PUBLISHED, msg_id=41464
I (4484) MQTT_EXAMPLE: MQTT_EVENT_SUBSCRIBED, msg_id=17886
I (4484) MQTT_EXAMPLE: sent publish successful, msg_id=0
I (4684) MQTT_EXAMPLE: MQTT_EVENT_SUBSCRIBED, msg_id=42970
I (4684) MQTT_EXAMPLE: sent publish successful, msg_id=0
I (4884) MQTT_CLIENT: deliver_publish, message_length_read=19, message_length=19
I (4884) MQTT_EXAMPLE: MQTT_EVENT_DATA
TOPIC=/topic/qos0
DATA=data
I (5194) MQTT_CLIENT: deliver_publish, message_length_read=19, message_length=19
I (5194) MQTT_EXAMPLE: MQTT_EVENT_DATA
TOPIC=/topic/qos0
DATA=data
```