Company B runs a business directory with a social-media-style marketplace on Azure, built with Blazor Server and SignalR. How does the application talk to the browser, and which company rule makes this a security case?

With Blazor Server the main logic runs on the server and the browser is a thin client: it loads only small pages, and all further updates travel over a SignalR connection, a WebSocket link between client and server. A company-wide policy demands that every web presence be protected by a web application firewall.

* After the first small page, everything runs over one long-lived socket rather than separate HTTP requests. *

The case: tradespeople register in the directory and offer their services on a digital marketplace; registered customers visit it and exchange messages with traders and with each other. Company B lives on the trust of its marketplace participants, so it takes cyber security seriously. The flow:

1. (0) The user calls https://b.marktplatz.ch; a listener on port 443 in B's Azure tenant accepts it.
2. (1) The Blazor server builds a small page and sends it to the browser.
3. (2) The page opens a socket connection (WebSocket over HTTPS) back to the server.
4. (3) All data transfer and UI updates flow over that socket in both directions.

Blazor is Microsoft's open-source framework for web applications and comes in several variants; Blazor Server is the one where the code stays on the server. SignalR is the open-source library that provides the WebSocket communication.

Go deeper:

• Microsoft Learn — ASP.NET Core Blazor hosting models — how Blazor Server keeps the code on the server and sends UI updates over SignalR.
• Microsoft Learn — Overview of ASP.NET Core SignalR — the real-time library and its transports.
• WebSocket — Wikipedia — the long-lived, two-way protocol behind the socket connection.