cara mengatasi masalah cannot declare variable 'server' to be of abstract type 'EthernetServer'

 If new arduino esp32 or make error, need go to c:\Program Files (x86)\Arduino\hardware\espressif\arduino-esp32\cores\esp32\Server.h

Change virtual void begin(uint16_t port = 0) = 0; to virtual void begin() = 0;