You most certainly CAN utilize WebSockets from desktop applications in Java, outside the browser sandbox. The thinking behind this is that you can create thick clients that create TCP connections, so of course they should be able to create WebSocket connections on top of those TCP connections.
One of the newest and best APIs for doing so is written by Kaazing, taking the point of view that a WebSocket is just like a socket and can be created using simple "ws://" URIs.
The API is discussed in detail on the Kaazing Gateway 5.0 Java WebSocket Documentation site. You can download the plain Gateway from Kaazing here
Create a websocket:
import com.kaazing.net.ws.WebSocket;
import com.kaazing.net.ws.WebSocketFactory;
wsFactory = WebSocketFactory.createWebSocketFactory();
ws = wsFactory.createWebSocket(URI.create("ws://example.com:8001/path"));
ws.connect(); // This will block or throw an exception if failed.
To send messages, add a WebSocketMessageWriter object:
WebSocketMessageWriter writer = ws.getMessageWriter();
String text = "Hello WebSocket!";
writer.writeText(text); // Send text message
To receive or consume messages, add WebSocket and WebSocketMessageReader objects:
wsFactory = WebSocketFactory.createWebSocketFactory();
ws = wsFactory.createWebSocket(URI.create("ws://example.com:8001/path"));
ws.connect(); // This will block or throw an exception if failed.
WebSocketMessageReader reader = ws.getMessageReader();
WebSocketMessageType type = null; // Block till a message arrives
// Loop till the connection goes away
while ((type = reader.next()) != WebSocketMessageType.EOS) {
switch (type) { // Handle both text and binary messages
case TEXT:
CharSequence text = reader.getText();
log("RECEIVED TEXT MESSAGE: " + text.toString());
break;
case BINARY:
ByteBuffer buffer = reader.getBinary();
log("RECEIVED BINARY MESSAGE: " + getHexDump(buffer));
break;
}
}
(Full Disclosure: I used to work at Kaazing Corporation as a server engineer.)
