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| </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="jetty-websocket-api-events"></a>WebSocket Events</h2></div></div></div><p>Every WebSocket can receive various events:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">On Connect Event</span></dt><dd><p class="simpara">An indication to the WebSocket that the Upgrade has succeeded and the WebSocket is now open.</p><p class="simpara">You will receive a <a class="link" href="http://www.eclipse.org/jetty/javadoc/9.3.28.v20191105/org/eclipse/jetty/websocket/api/Session.html" target="_top"><code class="literal">org.eclipse.jetty.websocket.api.Session</code></a> object that references the specific session for this Open Event.</p><p class="simpara">For normal WebSockets, it is important to hold onto this Session and use it for communicating with the Remote Endpoint.</p><p class="simpara">For Stateless WebSockets, the Session will be passed into each event as it occurs, allowing you to only have 1 instance of a WebSocket serving many Remote Endpoints.</p></dd><dt><span class="term">On Close Event</span></dt><dd><p class="simpara">An indication that the WebSocket is now closed.</p><p class="simpara">Every Close Event will have a <a class="link" href="http://www.eclipse.org/jetty/javadoc/9.3.28.v20191105/org/eclipse/jetty/websocket/api/StatusCode.html" target="_top">Status Code</a> (and an optional Closure Reason Message)</p><p class="simpara">A normal WebSocket closure will go through a Close Handshake where both the Local Endpoint and the Remote Endpoint both send a Close frame to indicate that the connection is closed.</p><p class="simpara">It is possible for the Local WebSocket to indicate its desire to Close by issuing a Close frame to the Remote Endpoint, but the Remote Endpoint can continue to send messages until it sends a Close Frame. |
| This is known as a Half-Open connection, and it is important to note that once the Local Endpoint has send the Close Frame it cannot write anymore WebSocket traffic.</p><p class="simpara">On an abnormal closure, such as a connection disconnect or a connection timeout, the low level connection will be terminated without going through a Close Handshake, this will still result in an On Close Event (and likely a corresponding On Error Event).</p></dd><dt><span class="term">On Error Event</span></dt><dd>If an error occurred, during the implementation, the WebSocket will be notified via this event handler.</dd><dt><span class="term">On Message Event</span></dt><dd><p class="simpara">An indication that a complete message has been received and is ready for handling by your WebSocket.</p><p class="simpara">This can be a (UTF8) TEXT message or a raw BINARY message.</p></dd></dl></div></div><script type="text/javascript"> |
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