ESP8266 Community Forum

- Sun Apr 30, 2017 2:53 am #65411 I am using AsyncMqttClient and have a String payloadStr which ends up containing a two-word sentence e.g. "Open Open". I have spent several days trying to cast this into payload but have not asked the correct question of Google. I know

mqttClient.publish(MQTT_FEEDBACK_TOPIC, 0, true, "Open Open")

works and is processed by Node-Red correctly but

mqttClient.publish(MQTT_FEEDBACK_TOPIC, 0, true, payloadStr)

(plus many variations I have tried) returns an exit status
no matching function for call to 'AsyncMqttClient::publish(const char [19], int, bool, String&)
which I can't interpret. I understand payload.length computes itself when a string is passed so I have omitted this.

- Mon May 01, 2017 11:12 pm #65461 You did not mention the data type of payloadStr. However, if it is declared as type String as in

Code: Select allString payloadStr;

then the following might work.

Code: Select allmqttClient.publish(MQTT_FEEDBACK_TOPIC, 0, true, payloadStr.c_str())

- Fri Apr 03, 2020 5:06 am #86324 OK, this is an old question, today for me it was new.
Thank You, it worked.