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# ESP-MQTT MQTT over WSS Sample application
(See the README.md file in the upper level 'examples' directory for more information about examples.)
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This example connects to the broker mqtt.eclipseprojects.io over secure websockets and as a demonstration subscribes/unsubscribes and send a message on certain topic.
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(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 ))
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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
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* Open the project configuration menu (`idf.py menuconfig`)
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* 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.
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Note how to create a PEM certificate for mqtt.eclipseprojects.io:
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PEM certificate for this example could be extracted from an openssl `s_client` command connecting to mqtt.eclipseprojects.io.
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In case a host operating system has `openssl` and `sed` packages installed, one could execute the following command to download and save the root certificate to a file (Note for Windows users: Both Linux like environment or Windows native packages may be used).
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```
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echo "" | openssl s_client -showcerts -connect mqtt.eclipseprojects.io:443 | sed -n "1,/Root/d; /BEGIN/,/END/p" | openssl x509 -outform PEM >mqtt_eclipse_org.pem
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```
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Please note that this is not a general command for downloading a root certificate for an arbitrary host;
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this command works with mqtt.eclipseprojects.io as the site provides root certificate in the chain, which then could be extracted
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with text operation.
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### Build and Flash
Build the project and flash it to the board, then run monitor tool to view serial output:
```
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idf.py -p PORT flash monitor
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```
(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) MQTTWSS_EXAMPLE: MQTT_EVENT_CONNECTED
I (4174) MQTTWSS_EXAMPLE: sent publish successful, msg_id=41464
I (4174) MQTTWSS_EXAMPLE: sent subscribe successful, msg_id=17886
I (4174) MQTTWSS_EXAMPLE: sent subscribe successful, msg_id=42970
I (4184) MQTTWSS_EXAMPLE: sent unsubscribe successful, msg_id=50241
I (4314) MQTTWSS_EXAMPLE: MQTT_EVENT_PUBLISHED, msg_id=41464
I (4484) MQTTWSS_EXAMPLE: MQTT_EVENT_SUBSCRIBED, msg_id=17886
I (4484) MQTTWSS_EXAMPLE: sent publish successful, msg_id=0
I (4684) MQTTWSS_EXAMPLE: MQTT_EVENT_SUBSCRIBED, msg_id=42970
I (4684) MQTTWSS_EXAMPLE: sent publish successful, msg_id=0
I (4884) MQTT_CLIENT: deliver_publish, message_length_read=19, message_length=19
I (4884) MQTTWSS_EXAMPLE: MQTT_EVENT_DATA
TOPIC=/topic/qos0
DATA=data
I (5194) MQTT_CLIENT: deliver_publish, message_length_read=19, message_length=19
I (5194) MQTTWSS_EXAMPLE: MQTT_EVENT_DATA
TOPIC=/topic/qos0
DATA=data
```
