sis"><em>composed asynchronous operation</em></span>,
            is implemented in terms of calls to the next layer's <code class="computeroutput"><span class="identifier">async_read_some</span></code>
            and <code class="computeroutput"><span class="identifier">async_write_some</span></code>
            functions. No other operation may be performed on the stream until this
            operation completes. If a valid upgrade request is received, an HTTP
            response with a <a href="https: