I am trying to insert a string into a char with concatenation and not getting any love from the Arduino compiler. It is over my head. Here is the code: String strClient_id = "ESP8266-"+WiFi.macAddress().substring(9,11) +WiFi.macAddress().substring(12,14) …

Char initialized as concatenation of String +String variables generates error

UKHeliBob October 5, 2017, 4:41pm 13

ESP8266WiFi.h returns a string.

Do you mean a string or a String ?