Added a discovery support by listening to UDP.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@15122 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/UDPBroadcastThread.java

@@ -0,0 +1,100 @@
+/*
+ * The MIT License
+ *
+ * Copyright (c) 2004-2009, Sun Microsystems, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package hudson;
+
+import hudson.model.Hudson;
+
+import java.io.IOException;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
+import java.nio.ByteBuffer;
+import java.nio.channels.ClosedByInterruptException;
+import java.nio.channels.DatagramChannel;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ * Monitors a UDP broadcast and respond with the location of the Hudson service.
+ *
+ * <p>
+ * Useful for auto-discovery of Hudson in the network.
+ *
+ * @author Kohsuke Kawaguchi
+ */
+public class UDPBroadcastThread extends Thread {
+    private final Hudson hudson;
+    public UDPBroadcastThread(Hudson hudson) {
+        super("Hudson UDP "+PORT+" monitoring thread");
+        this.hudson = hudson;
+    }
+
+    @Override
+    public void run() {
+        try {
+            DatagramChannel ch = DatagramChannel.open();
+            try {
+                ch.socket().bind(new InetSocketAddress(PORT));
+
+                ByteBuffer b = ByteBuffer.allocate(2048);
+                while(true) {
+                    // the only thing that matters here is who sent it, not what was sent.
+                    SocketAddress sender = ch.receive(b);
+
+                    // prepare a response
+                    TcpSlaveAgentListener tal = hudson.getTcpSlaveAgentListener();
+
+                    StringBuilder buf = new StringBuilder("<hudson>");
+                    tag(buf,"version",Hudson.VERSION);
+                    tag(buf,"url",hudson.getRootUrl());
+                    tag(buf,"slave-port",tal==null?null:tal.getPort());
+                    buf.append("</hudson>");
+
+                    b.clear();
+                    b.put(buf.toString().getBytes("UTF-8"));
+                    b.flip();
+                    ch.send(b, sender);
+                }
+            } finally {
+                ch.close();
+            }
+        } catch (ClosedByInterruptException e) {
+            // shut down
+        } catch (IOException e) {
+            LOGGER.log(Level.WARNING, "UDP handling problem",e);
+        }
+    }
+
+    private void tag(StringBuilder buf, String tag, Object value) {
+        if(value==null) return;
+        buf.append('<').append(tag).append('>').append(value).append("</").append(tag).append('>');
+    }
+
+    public void shutdown() {
+        interrupt();
+    }
+
+    public static final int PORT = Integer.getInteger("hudson.udp",33848);
+
+    private static final Logger LOGGER = Logger.getLogger(UDPBroadcastThread.class.getName());
+}