The mobile app to/from Blynk cloud server and web dashboard to/from Blynk cloud server protocols are not publicly available.
The communication between the device and the cloud server is proprietary, across a keep-alive ssl/tls connection on port 443 or plain tcp/ip connection on port 80.
If you enable debugging in a C++ sketch you can see the data that is transferred between the device and cloud server. More info here…