ESP32 IDF开发-ESP32 MQTT_TCP例程

# 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 `idf.py 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: ``` idf.py -p PORT 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 ```