I have an ASP.NET Core application that provides a SignalR hub for real-time notifications. I used the SignalR hub as a WebSocket endpoint with a self-hosted SignalR server. Using the WebSocket package in my Flutter web application, I could connect to the hub, receive notifications, and even test the connection using Postman.

Recently, I migrated from the self-hosted SignalR setup to Azure SignalR Service. Now, my Flutter web app and Postman can no longer connect to the same endpoint, wss://example/chat-hub. The connection fails during the handshake, and I cannot even establish a WebSocket connection using Postman.

I have followed this tutorial to migrate from self-hosted SignalR to Azure SignalR service