fixed #49

protocol/src/main/java/ch/zhaw/pm2/multichat/protocol/Message.java

@@ -1,9 +1,11 @@
 package ch.zhaw.pm2.multichat.protocol;
 
+import java.io.Serializable;
+
 /**
  * A Message object represents one Message of a client. Can be stored in ClientMessageList.
  */
-public class Message {
+public class Message implements Serializable {
     private final ConnectionHandler.DATA_TYPE type;
     private String sender;
     private final String receiver;

protocol/src/main/java/ch/zhaw/pm2/multichat/protocol/NetworkHandler.java

@@ -320,9 +320,9 @@ public class NetworkHandler {
          * @throws IOException if an error occours. (e.g. terminated locally/remotely) see above.
          * @throws ClassNotFoundException if the data object received does not match any class in the local classpath
          */
-        public T receive() throws IOException, ClassNotFoundException {
+        public Message receive() throws IOException, ClassNotFoundException {
             ObjectInputStream inputStream = new ObjectInputStream(this.socket.getInputStream());
-            return (T) inputStream.readObject();
+            return (Message) inputStream.readObject();
         }
 
         /**