MQTT Payload data type

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1

The pubsubclient.h files defines the publish call as:

boolean publish(const char* topic, const char* payload);
boolean publish(const char* topic, const char* payload, boolean retained);

If I call it with:

client.publish("mytopic", "0")

I get a warning:

C++ forbids converting a string constant to 'char*'

Short of sifting the code to define a 0 and 1 as chars, such as

const char ON = "1";
const char OFF = "0";

Then amending the calls to be:

client.publish("mytopic", OFF)

I am not certain how to remove the warning as the "0" or "1" are not variables, but simple values. Perhaps I am missing some point.

2

Okay. Having tested it with ON/OFF as const char, it still gives the error with the topic.

3

Solved. Was the conversion from char* to const char* that was throwing it and I had omitted it in a MQTT publish function.