Added a service that will send the server's serializer

registration set to each new client that connects.  The
client-side version of this service will then register them
all.  This means that serialized classes need only be registered
on the server.
I've modified DefaultClient and DefaultServer to register these
services by default because they make other services easier to
write and because they will save people lots of trouble.
I'm 90% sure there are no bad side-effects for people who choose
to continue doing things the old way but it may depend on when
they register their serializers in relations to creating the
client and server objects.

jme3-networking/src/main/java/com/jme3/network/base/DefaultClient.java

@@ -38,6 +38,7 @@ import com.jme3.network.message.ChannelInfoMessage;
 import com.jme3.network.message.ClientRegistrationMessage;
 import com.jme3.network.message.DisconnectMessage;
 import com.jme3.network.service.ClientServiceManager;
+import com.jme3.network.service.serializer.ClientSerializerRegistrationsService;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.*;
@@ -88,6 +89,7 @@ public class DefaultClient implements Client
         this.gameName = gameName;
         this.version = version;
         this.services = new ClientServiceManager(this);
+        addStandardServices();
     }
     
     public DefaultClient( String gameName, int version, Connector reliable, Connector fast,
@@ -97,6 +99,10 @@ public class DefaultClient implements Client
         setPrimaryConnectors( reliable, fast, connectorFactory );
     }
 
+    protected void addStandardServices() {
+        services.addService(new ClientSerializerRegistrationsService());
+    }
+
     protected void setPrimaryConnectors( Connector reliable, Connector fast, ConnectorFactory connectorFactory )
     {
         if( reliable == null )

jme3-networking/src/main/java/com/jme3/network/base/DefaultServer.java

@@ -38,6 +38,7 @@ import com.jme3.network.message.ChannelInfoMessage;
 import com.jme3.network.message.ClientRegistrationMessage;
 import com.jme3.network.message.DisconnectMessage;
 import com.jme3.network.service.HostedServiceManager;
+import com.jme3.network.service.serializer.ServerSerializerRegistrationsService;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.*;
@@ -95,7 +96,8 @@ public class DefaultServer implements Server
             
         this.gameName = gameName;
         this.version = version;
-        this.services = new HostedServiceManager(this);
+        this.services = new HostedServiceManager(this);        
+        addStandardServices();
         
         reliableAdapter = new KernelAdapter( this, reliable, dispatcher, true );
         channels.add( reliableAdapter );
@@ -105,6 +107,10 @@ public class DefaultServer implements Server
         }
     }   
 
+    protected void addStandardServices() {
+        services.addService(new ServerSerializerRegistrationsService());
+    }
+
     public String getGameName()
     {
         return gameName;

jme3-networking/src/main/java/com/jme3/network/service/ClientServiceManager.java

@@ -75,6 +75,19 @@ public class ClientServiceManager extends ServiceManager<ClientServiceManager> {
         super.addService(s);
     }
 
+    /**
+     *  Adds all of the specified ClientServices and initializes them.  If the service manager
+     *  has already been started then the services will also be started.
+     *  This is a convenience method that delegates to addService(), thus each
+     *  service will be initialized (and possibly started) in sequence rather
+     *  than doing them all at the end.
+     */   
+    public void addServices( ClientService... services ) {
+        for( ClientService s : services ) {
+            super.addService(s);
+        }
+    }
+
     /**
      *  Removes the specified ClientService from this service manager, stopping
      *  and terminating it as required.  If this service manager is in a

jme3-networking/src/main/java/com/jme3/network/service/HostedServiceManager.java

@@ -82,6 +82,19 @@ public class HostedServiceManager extends ServiceManager<HostedServiceManager> {
         super.addService(s);
     }
 
+    /**
+     *  Adds all of the specified HostedServices and initializes them.  If the service manager
+     *  has already been started then the services will also be started.
+     *  This is a convenience method that delegates to addService(), thus each
+     *  service will be initialized (and possibly started) in sequence rather
+     *  than doing them all at the end.
+     */   
+    public void addServices( HostedService... services ) {
+        for( HostedService s : services ) {
+            super.addService(s);
+        }
+    }
+
     /**
      *  Removes the specified HostedService from this service manager, stopping
      *  and terminating it as required.  If this service manager is in a

jme3-networking/src/main/java/com/jme3/network/service/serializer/ClientSerializerRegistrationsService.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2015 jMonkeyEngine
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
+ *   may be used to endorse or promote products derived from this software
+ *   without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.jme3.network.service.serializer;
+
+import com.jme3.network.Client;
+import com.jme3.network.Message;
+import com.jme3.network.MessageListener;
+import com.jme3.network.message.SerializerRegistrationsMessage;
+import com.jme3.network.serializing.Serializer;
+import com.jme3.network.service.AbstractClientService;
+import com.jme3.network.service.ClientServiceManager;
+
+
+/**
+ *
+ *
+ *  @author    Paul Speed
+ */
+public class ClientSerializerRegistrationsService extends AbstractClientService 
+                                                  implements MessageListener<Client> {
+
+    @Override
+    protected void onInitialize( ClientServiceManager serviceManager ) {
+        // Make sure our message type is registered
+        // This is the minimum we'd need just to be able to register
+        // the rest... otherwise we can't even receive this message.
+        Serializer.registerClass(SerializerRegistrationsMessage.class);
+        
+        // Add our listener for that message type
+        serviceManager.getClient().addMessageListener(this, SerializerRegistrationsMessage.class); 
+    }
+
+    public void messageReceived( Client source, Message m ) {
+        // We only wait for one kind of message...
+        SerializerRegistrationsMessage msg = (SerializerRegistrationsMessage)m;
+        msg.registerAll();
+    }    
+}

jme3-networking/src/main/java/com/jme3/network/service/serializer/ServerSerializerRegistrationsService.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright (c) 2015 jMonkeyEngine
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright
+ *   notice, this list of conditions and the following disclaimer in the
+ *   documentation and/or other materials provided with the distribution.
+ *
+ * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
+ *   may be used to endorse or promote products derived from this software
+ *   without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.jme3.network.service.serializer;
+
+import com.jme3.network.HostedConnection;
+import com.jme3.network.Server;
+import com.jme3.network.message.SerializerRegistrationsMessage;
+import com.jme3.network.serializing.Serializer;
+import com.jme3.network.service.AbstractHostedService;
+import com.jme3.network.service.HostedServiceManager;
+
+
+/**
+ *
+ *
+ *  @author    Paul Speed
+ */
+public class ServerSerializerRegistrationsService extends AbstractHostedService {
+
+    @Override
+    protected void onInitialize( HostedServiceManager serviceManager ) {
+        // Make sure our message type is registered
+        Serializer.registerClass(SerializerRegistrationsMessage.class);
+    }
+    
+    @Override
+    public void start() {
+        // Compile the registrations into a message we will
+        // send to all connecting clients
+        SerializerRegistrationsMessage.compile();
+    }
+    
+    @Override
+    public void connectionAdded(Server server, HostedConnection hc) {
+        // Just in case
+        super.connectionAdded(server, hc);
+        
+        // Send the client the registration information
+        hc.send(SerializerRegistrationsMessage.INSTANCE);
+    }
+}