 HTTP/1.1 Upgrade header

The `Upgrade` header in HTTP/1.1 is used to indicate that the client wishes to change the protocol to a different one. This is commonly used for protocols that operate over a TCP connection, allowing for more sophisticated communication setups such as switching to WebSocket or HTTP/2. Here’s how the `Upgrade` header typically works: 1. **Requesting a Protocol Change**: A client (like a web browser) makes an HTTP/1.