Messaging adjusted, SwitchPort added.

JSimpleSim/.classpath

@@ -1,12 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <classpath>
-	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8">
+	<classpathentry exported="true" kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.8">
 		<attributes>
 			<attribute name="module" value="true"/>
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry kind="src" output="target/classes" path="src">
+	<classpathentry kind="src" path="src">
 		<attributes>
 			<attribute name="optional" value="true"/>
 			<attribute name="maven.pomderived" value="true"/>
@@ -17,5 +17,5 @@
 			<attribute name="maven.pomderived" value="true"/>
 		</attributes>
 	</classpathentry>
-	<classpathentry kind="output" path="target/classes"/>
+	<classpathentry kind="output" path="bin"/>
 </classpath>

JSimpleSim/.gitignore

@@ -0,0 +1 @@
+/bin/

JSimpleSim/src/org/simplesim/core/messaging/Message.java

@@ -14,7 +14,8 @@
 /**
  * Base class for messages that are sent from one port to another.
  * <p>
- * Messages always contain a content and may be extended with additional features.
+ * Messages always contain a content and may be extended with additional features. If agents are
+ * connected <i>directly</i>, the destination can be omitted and set to {@code null}. 
  * 
  * @param <A> type of addressing
  *