This Network Entry Point is for test purposes. To run the test program, you have to open the file Network.gwt.xml, and uncomment the line
<entry-point class='com.chap.links.client.NetworkEntryPoint'/>
such that the entry point is defined.
If you want to create a stand-alone module for the network you have to comment the line with the entry point again, and then create a jar containing only Network.java, Network.gwt.xml, network.js.