In it, he shows an example of using all three ESP32 UARTs from an Arduino program. He calls the third port “secret” although that’s really a misnomer.

While the Arduino family of boards connect to your computer using a USB virtual serial port, the ATmega ones have an actual serial connection on-board.

Serial Port Monitor from Eltima The Serial Port Monitor software tool from Eltima Software is, in fact, a professional port sniffer and analyzer system utility good for RS232/RS422/RS485 port ...