Refactor and test Variable Server.

- Split VariableServerThread into VariableServerSession and VariableReference classes
- Use C++ streams for data handling
- Unit tests

trick_source/java/src/main/java/trick/simcontrol/SimControlApplication.java

@@ -1572,6 +1572,7 @@ public class SimControlApplication extends TrickApplication implements PropertyC
         @Override
         protected void finished() {
             try {
+                System.out.println("Finished with health status socket channel");
                 if (healthStatusSocketChannel != null) {
                     healthStatusSocketChannel.close() ;
                 }
@@ -1606,7 +1607,11 @@ public class SimControlApplication extends TrickApplication implements PropertyC
 
                     if (statusSimcom != null) {
 
-                        results = statusSimcom.get().split("\t");
+                        String resultsStr = statusSimcom.get();
+                        if (resultsStr == null) 
+                            break;
+
+                        results = resultsStr.split("\t");
                         ii = 1 ;
 
                         // whenever there is data in statusSimcom socket, do something

trick_source/java/src/main/java/trick/simcontrol/utils/SimControlActionController.java

@@ -295,7 +295,7 @@ public class SimControlActionController {
                 simcom.put("trick.debug_pause_off()\n" ) ;
             }
         } catch (IOException e) {
-            System.out.println("Put failed!");
+            System.out.println("Put failed! Exception: " + e.getMessage());
         }
     }