diff --git a/src/se/hal/deamon/PCDataSynchronizationClient.java b/src/se/hal/deamon/PCDataSynchronizationClient.java
index 47b2b309..04aabfdc 100755
--- a/src/se/hal/deamon/PCDataSynchronizationClient.java
+++ b/src/se/hal/deamon/PCDataSynchronizationClient.java
@@ -49,6 +49,15 @@ public class PCDataSynchronizationClient implements HalDaemon {
 					ObjectOutputStream out = new ObjectOutputStream(s.getOutputStream());
 					ObjectInputStream in = new ObjectInputStream(s.getInputStream());
 
+					// Check server protocol version
+                    int version = in.readInt();
+                    if(version != PCDataSynchronizationDaemon.PROTOCOL_VERSION){
+                        logger.warning("Protocol version do not match, skipping user. " +
+                                "(local v"+PCDataSynchronizationDaemon.PROTOCOL_VERSION+" != remote v"+version+")");
+                        out.writeObject(null); // Tell server we are disconnecting
+                        continue;
+                    }
+
                     // Request peer data
                     out.writeObject(new PeerDataReqDTO());
                     PeerDataRspDTO peerData = (PeerDataRspDTO) in.readObject();
@@ -98,10 +107,7 @@ public class PCDataSynchronizationClient implements HalDaemon {
                             logger.fine("Skipped sensor " + sensor.getId());
 					}
 					out.writeObject(null); // Tell server we are disconnecting
-					out.close();
-					in.close();
-					s.close();
-					
+
 				} catch (NoRouteToHostException|UnknownHostException|ConnectException e) {
 					logger.warning("Unable to connect to "+ user.getHostname()+":"+user.getPort() +", "+ e.getMessage());
 				} catch (Exception e) {
diff --git a/src/se/hal/deamon/PCDataSynchronizationDaemon.java b/src/se/hal/deamon/PCDataSynchronizationDaemon.java
index 94ad74c5..8d4d64b1 100755
--- a/src/se/hal/deamon/PCDataSynchronizationDaemon.java
+++ b/src/se/hal/deamon/PCDataSynchronizationDaemon.java
@@ -28,6 +28,7 @@ import java.util.logging.Logger;
 
 public class PCDataSynchronizationDaemon extends ThreadedTCPNetworkServer implements HalDaemon {
 	private static final Logger logger = LogUtil.getLogger();
+    public static final int PROTOCOL_VERSION = 2;
 
 
 	public PCDataSynchronizationDaemon() {
@@ -71,6 +72,7 @@ public class PCDataSynchronizationDaemon extends ThreadedTCPNetworkServer implem
 
 			try {
 				Object obj = null;
+                out.writeInt(PROTOCOL_VERSION); // send our protocol version to client
 				while((obj = in.readObject()) != null){
                     if(obj instanceof PeerDataReqDTO){
                         logger.fine("Client requesting peer data");