Websocket Part:

Connect to websocket_url

Send subscribe message, example:

{
  "command": "subscribe",
  "identifier": "{\"channel\":\"BynnKycChannel\"}"
}

After subscribe message you will automaticly get the preflight payload, then you will get it on all event changes.
Example:

{
    "identifier": "{\"channel\":\"BynnKycChannel\"}",
    "message": {
        "extra_data": {},
        "session": "cTMKciZaG4iv7FfRZk1nxRW1",
        "session_id": "cTMKciZaG4iv7FfRZk1nxRW1",
        "entity_id_state": "none_received",
        "entity_id_document_type": "unknown",
        "requirement": {
            "requirement_type": "identity_document",
            "status": "awaiting_receipt",
            "flow_order": 100
        },
        "screen": {
            "show": "scan_id_document_front_screen",
            "parameters": {
                "camera": "back",
                "camera_quality": "ultra",
                "allow_manual_upload": false,
                "multipage": false,
                "title": null,
                "text": null
            }
        }
    }
}