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BTW, to convert String to char * easily, there are methods provided :

I'm using the same method in my sketches, and it is working on my side.
So, maybe the problem is on the router side, maybe it have cache an kept the old name used before.
Try to power recycle the router to see if it help.

martinayotte wrote:BTW, to convert String to char * easily, there are methods provided :

Code: Select allString routername = "Testing123";
wifi_station_set_hostname(routername.c_str());


I tried that but I got this error

error: invalid conversion from 'const char*' to 'char*' [-fpermissive]

Yes, you are right !
But it need a simple cast to fix the error :

This compiles, but still does not change the name seen by the router. I powered off/on the router and that made no difference. I am using AP mode, not station mode. Is this this the difference?