t>
<dd>The results of the send operation. If it returns an empty set, then there was no open web socket session
 associated with given socket channel and user. The returned futures will return <code>null</code> on
 <a href="https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/concurrent/Future.html#get()" title="class or interface in java.util.concurrent" class="external-link"><code>Future.get()</code></a> if the message was successfully delivered and otherwise throw <a href="https://docs.