101 Switching Protocols

The server understands and is willing to comply with the client request, through the Upgrade message header field ([RFC 2068], section 14.42), for a change in the application protocol being used on this connection. The server will switch protocols to those defined by the response of the Upgrade header field immediately after the empty line which terminates the 101 response.

The protocol SHOULD be switched only when it is advantageous to do so. For example, switching to a newer version of HTTP is advantageous over older versions, and switching to a real-time, synchronous protocol might be advantageous when delivering resources that use such features.

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