What do initial bytes from client mean?

[guest271314]

I'm working on creating a WebTransport server in an Isolated Web App (IWA) using only Direct SOckets UDPSocket and Web API's (specifically Web Cryptography API to handle handshake and packet decryption).

When the Chromium WebTransport() constructor is initialized I get four (4) Uint8Array's, each having exactly 1250 length. 

Right now I'm getting this error message in the client:

Failed to establish a connection to https://127.0.0.1:4433/: net::ERR_QUIC_PROTOCOL_ERROR.QUIC_NETWORK_IDLE_TIMEOUT (No recent network activity after 4000494us. Timeout:4s num_undecryptable_packets: 0 {}).

What does the data in those 4 Uint8Array's represent, and what response is the Chromium WebTransport client expecting to establish the connection?

E.g.,

data: Uint8Array(1250) [201, 0, 0, 0, 1, 8, 99, 176, 113, 233,...

data: Uint8Array(1250) [202, 0, 0, 0, 1, 8, 99, 176, 113, 233,...

data: Uint8Array(1250) [203, 0, 0, 0, 1, 8, 99, 176, 113, 233,...

data: Uint8Array(1250) [203, 0, 0, 0, 1, 8, 99, 176, 113, 233,...