ESP32 OTA information

We want to take advantage of PlatformIO’s OTA feature. I.E.
upload_protocol = espota
upload_port = IP_ADDRESS_HERE or mDNS_NAME.local

We do not want to use Arduino, and will use IDF.
We will create our own server to accept the connection. Is there any information on how and what is sent so we know what we will need to reply back with ?