diff --git a/src/java/com/threerings/presents/client/BlockingCommunicator.java b/src/java/com/threerings/presents/client/BlockingCommunicator.java
index d4b35415c..d7c41697c 100644
--- a/src/java/com/threerings/presents/client/BlockingCommunicator.java
+++ b/src/java/com/threerings/presents/client/BlockingCommunicator.java
@@ -56,6 +56,7 @@ import com.threerings.presents.net.AuthResponseData;
 import com.threerings.presents.net.DownstreamMessage;
 import com.threerings.presents.net.LogoffRequest;
 import com.threerings.presents.net.PingRequest;
+import com.threerings.presents.net.TransmitDatagramsRequest;
 import com.threerings.presents.net.Transport;
 import com.threerings.presents.net.UpstreamMessage;
 import com.threerings.presents.util.DatagramSequencer;
@@ -766,6 +767,9 @@ public class BlockingCommunicator extends Communicator
             if (cport > 0) {
                 log.info("Datagram connection established", "port", cport);
 
+                // notify the server
+                postMessage(new TransmitDatagramsRequest());
+
                 // start up the writer thread
                 _datagramWriter = new DatagramWriter();
                 _datagramWriter.start();
diff --git a/src/java/com/threerings/presents/net/TransmitDatagramsRequest.java b/src/java/com/threerings/presents/net/TransmitDatagramsRequest.java
new file mode 100644
index 000000000..05e3321d4
--- /dev/null
+++ b/src/java/com/threerings/presents/net/TransmitDatagramsRequest.java
@@ -0,0 +1,34 @@
+//
+// $Id$
+//
+// Narya library - tools for developing networked games
+// Copyright (C) 2002-2007 Three Rings Design, Inc., All Rights Reserved
+// http://www.threerings.net/code/narya/
+//
+// This library is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License as published
+// by the Free Software Foundation; either version 2.1 of the License, or
+// (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+package com.threerings.presents.net;
+
+/**
+ * Notifies the server that we would like it to send us datagrams.
+ */
+public class TransmitDatagramsRequest extends UpstreamMessage
+{
+    @Override
+    public String toString ()
+    {
+        return "[type=TRANSMIT_DATAGRAMS, msgid=" + messageId + "]";
+    }
+}
diff --git a/src/java/com/threerings/presents/server/PresentsSession.java b/src/java/com/threerings/presents/server/PresentsSession.java
index f9b1ba17a..10561c895 100644
--- a/src/java/com/threerings/presents/server/PresentsSession.java
+++ b/src/java/com/threerings/presents/server/PresentsSession.java
@@ -63,6 +63,7 @@ import com.threerings.presents.net.PingRequest;
 import com.threerings.presents.net.PongResponse;
 import com.threerings.presents.net.SubscribeRequest;
 import com.threerings.presents.net.ThrottleUpdatedMessage;
+import com.threerings.presents.net.TransmitDatagramsRequest;
 import com.threerings.presents.net.UnsubscribeRequest;
 import com.threerings.presents.net.UnsubscribeResponse;
 import com.threerings.presents.net.UpdateThrottleMessage;
@@ -1085,6 +1086,18 @@ public class PresentsSession
         }
     }
 
+    /**
+     * Processes datagram transmission requests.
+     */
+    protected static class TransmitDatagramsDispatcher implements MessageDispatcher
+    {
+        public void dispatch (PresentsSession client, Message msg)
+        {
+            log.debug("Client requested datagram transmission", "client", client);
+            client.getConnection().setTransmitDatagrams(true);
+        }
+    }
+
     /**
      * Processes throttle updated messages.
      */
@@ -1158,6 +1171,7 @@ public class PresentsSession
         _disps.put(UnsubscribeRequest.class, new UnsubscribeDispatcher());
         _disps.put(ForwardEventRequest.class, new ForwardEventDispatcher());
         _disps.put(PingRequest.class, new PingDispatcher());
+        _disps.put(TransmitDatagramsRequest.class, new TransmitDatagramsDispatcher());
         _disps.put(ThrottleUpdatedMessage.class, new ThrottleUpdatedDispatcher());
         _disps.put(LogoffRequest.class, new LogoffDispatcher());
     }
diff --git a/src/java/com/threerings/presents/server/net/Connection.java b/src/java/com/threerings/presents/server/net/Connection.java
index 3f760cfa0..97a30b56d 100644
--- a/src/java/com/threerings/presents/server/net/Connection.java
+++ b/src/java/com/threerings/presents/server/net/Connection.java
@@ -121,6 +121,22 @@ public class Connection implements NetEventHandler
         return (_channel == null) ? null : _channel.socket().getInetAddress();
     }
 
+    /**
+     * Sets whether we should transmit datagrams.
+     */
+    public void setTransmitDatagrams (boolean transmit)
+    {
+        _transmitDatagrams = transmit;
+    }
+
+    /**
+     * Checks whether we should transmit datagrams.
+     */
+    public boolean getTransmitDatagrams ()
+    {
+        return _transmitDatagrams;
+    }
+
     /**
      * Returns the address to which datagrams should be sent or null if no datagram address has
      * been established.
@@ -435,6 +451,7 @@ public class Connection implements NetEventHandler
 
     protected InetSocketAddress _datagramAddress;
     protected byte[] _datagramSecret;
+    protected boolean _transmitDatagrams;
 
     protected MessageDigest _digest;
     protected DatagramSequencer _sequencer;
diff --git a/src/java/com/threerings/presents/server/net/ConnectionManager.java b/src/java/com/threerings/presents/server/net/ConnectionManager.java
index 0d2d378bc..08a39d71c 100644
--- a/src/java/com/threerings/presents/server/net/ConnectionManager.java
+++ b/src/java/com/threerings/presents/server/net/ConnectionManager.java
@@ -61,6 +61,7 @@ import com.threerings.presents.annotation.AuthInvoker;
 import com.threerings.presents.client.Client;
 import com.threerings.presents.data.ConMgrStats;
 import com.threerings.presents.net.Message;
+import com.threerings.presents.net.PongResponse;
 import com.threerings.presents.server.Authenticator;
 import com.threerings.presents.server.ChainedAuthenticator;
 import com.threerings.presents.server.ClientManager;
@@ -902,9 +903,11 @@ public class ConnectionManager extends LoopingThread
         }
 
         try {
-            // send it as a datagram if hinted and possible
-            if (!msg.getTransport().isReliable() && conn.getDatagramAddress() != null &&
-                    postDatagram(conn, msg)) {
+            // send it as a datagram if hinted and possible (pongs must be sent as part of the
+            // negotation process)
+            if (!msg.getTransport().isReliable() &&
+                    (conn.getTransmitDatagrams() || msg instanceof PongResponse) &&
+                        postDatagram(conn, msg)) {
                 return;
             }