esmp3/lib/pubsubclient/README.md

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# Arduino Client for MQTT
This library provides a client for doing simple publish/subscribe messaging with
a server that supports MQTT.
## Examples
The library comes with a number of example sketches. See File > Examples > PubSubClient
within the Arduino application.
Full API documentation is available here: https://pubsubclient.knolleary.net
## Limitations
- It can only publish QoS 0 messages. It can subscribe at QoS 0 or QoS 1.
- The maximum message size, including header, is **128 bytes** by default. This
is configurable via `MQTT_MAX_PACKET_SIZE` in `PubSubClient.h`.
- The keepalive interval is set to 15 seconds by default. This is configurable
via `MQTT_KEEPALIVE` in `PubSubClient.h`.
- The client uses MQTT 3.1.1 by default. It can be changed to use MQTT 3.1 by
changing value of `MQTT_VERSION` in `PubSubClient.h`.
## Compatible Hardware
The library uses the Arduino Ethernet Client api for interacting with the
underlying network hardware. This means it Just Works with a growing number of
boards and shields, including:
- Arduino Ethernet
- Arduino Ethernet Shield
- Arduino YUN use the included `YunClient` in place of `EthernetClient`, and
be sure to do a `Bridge.begin()` first
- Arduino WiFi Shield - if you want to send packets > 90 bytes with this shield,
enable the `MQTT_MAX_TRANSFER_SIZE` define in `PubSubClient.h`.
- Sparkfun WiFly Shield [library](https://github.com/dpslwk/WiFly)
- TI CC3000 WiFi - [library](https://github.com/sparkfun/SFE_CC3000_Library)
- Intel Galileo/Edison
- ESP8266
- ESP32
The library cannot currently be used with hardware based on the ENC28J60 chip
such as the Nanode or the Nuelectronics Ethernet Shield. For those, there is an
[alternative library](https://github.com/njh/NanodeMQTT) available.
## License
This code is released under the MIT License.