"Expected 'Upgrade' header value 'websocket' but was '$headerUpgrade'",
      )
    }

    val headerAccept = response.header("Sec-WebSocket-Accept")
    val acceptExpected = (key + WebSocketProtocol.ACCEPT_MAGIC).encodeUtf8().sha1().base64()
    if (acceptExpected != headerAccept) {
      throw ProtocolException(
        "Expected 'Sec-WebSocket-Accept' header value '$acceptExpected' but was '$headerAccept'",
      )
    }