Adding fingerprints to avoid interference between clusters.

Change-Id: I5e5278916f8b9b900d7d403b6d08f1f66a866fb2
diff --git a/utils/netty/src/main/java/org/onlab/netty/NettyMessaging.java b/utils/netty/src/main/java/org/onlab/netty/NettyMessaging.java
index 1cd7ca7..2dda747 100644
--- a/utils/netty/src/main/java/org/onlab/netty/NettyMessaging.java
+++ b/utils/netty/src/main/java/org/onlab/netty/NettyMessaging.java
@@ -74,6 +74,7 @@
     private static final String REPLY_MESSAGE_TYPE = "NETTY_MESSAGING_REQUEST_REPLY";
 
     private Endpoint localEp;
+    private int preamble;
     private final AtomicBoolean started = new AtomicBoolean(false);
     private final Map<String, Consumer<InternalMessage>> handlers = new ConcurrentHashMap<>();
     private final AtomicLong messageIdGenerator = new AtomicLong(0);
@@ -123,11 +124,12 @@
         clientChannelClass = NioSocketChannel.class;
     }
 
-    public void start(Endpoint localEp) throws Exception {
+    public void start(int preamble, Endpoint localEp) throws Exception {
         if (started.get()) {
             log.warn("Already running at local endpoint: {}", localEp);
             return;
         }
+        this.preamble = preamble;
         this.localEp = localEp;
         channels.setLifo(true);
         channels.setTestOnBorrow(true);
@@ -324,7 +326,7 @@
     private class SslServerCommunicationChannelInitializer extends ChannelInitializer<SocketChannel> {
 
         private final ChannelHandler dispatcher = new InboundMessageDispatcher();
-        private final ChannelHandler encoder = new MessageEncoder();
+        private final ChannelHandler encoder = new MessageEncoder(preamble);
 
         @Override
         protected void initChannel(SocketChannel channel) throws Exception {
@@ -351,7 +353,7 @@
 
             channel.pipeline().addLast("ssl", new io.netty.handler.ssl.SslHandler(serverSslEngine))
                     .addLast("encoder", encoder)
-                    .addLast("decoder", new MessageDecoder())
+                    .addLast("decoder", new MessageDecoder(preamble))
                     .addLast("handler", dispatcher);
         }
 
@@ -360,7 +362,7 @@
     private class SslClientCommunicationChannelInitializer extends ChannelInitializer<SocketChannel> {
 
         private final ChannelHandler dispatcher = new InboundMessageDispatcher();
-        private final ChannelHandler encoder = new MessageEncoder();
+        private final ChannelHandler encoder = new MessageEncoder(preamble);
 
         @Override
         protected void initChannel(SocketChannel channel) throws Exception {
@@ -386,7 +388,7 @@
 
             channel.pipeline().addLast("ssl", new io.netty.handler.ssl.SslHandler(clientSslEngine))
                     .addLast("encoder", encoder)
-                    .addLast("decoder", new MessageDecoder())
+                    .addLast("decoder", new MessageDecoder(preamble))
                     .addLast("handler", dispatcher);
         }
 
@@ -395,13 +397,13 @@
     private class OnosCommunicationChannelInitializer extends ChannelInitializer<SocketChannel> {
 
         private final ChannelHandler dispatcher = new InboundMessageDispatcher();
-        private final ChannelHandler encoder = new MessageEncoder();
+        private final ChannelHandler encoder = new MessageEncoder(preamble);
 
         @Override
         protected void initChannel(SocketChannel channel) throws Exception {
                 channel.pipeline()
                         .addLast("encoder", encoder)
-                        .addLast("decoder", new MessageDecoder())
+                        .addLast("decoder", new MessageDecoder(preamble))
                         .addLast("handler", dispatcher);
         }
     }
@@ -424,7 +426,6 @@
             context.close();
         }
     }
-
     private void dispatchLocally(InternalMessage message) throws IOException {
         String type = message.type();
         if (REPLY_MESSAGE_TYPE.equals(type)) {