is used to perform the <a href="https://en.wikipedia.org/wiki/WebSocket#Protocol_handshake" target="_top">WebSocket
            handshake</a>, required before messages can be sent and received.
            During the handshake, the client sends the Websocket Upgrade HTTP request,
            and the server replies with an HTTP response indicating the result of
            the handshake. The call blocks until one of the following conditions
            is true:
          </p>
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