I'm using ESP3, but it is not accepting callback functions. can anyone suggest me to resolve the issue so that i can able to gwt command from IBM cloud to ESP32.
sketch_oct20a:42:35: error: 'callback' was not declared in this scope
PubSubClient client(server, 1883, callback, wifiClient);
Multiple libraries were found for "WiFi.h"
Not used: C:\Program Files (x86)\Arduino\libraries\WiFi
exit status 1
'callback' was not declared in this scope