Implemented server re-registration when a server closes / updates

- When a server is closed, it will disappear from the server list
- When a player joins a server, the number of spaces left will decrease
- Servers now disappear instead of duplicating
- Added tests for ServerDescription
- Added documentation for new classes

Tags: #story[1247]

src/main/java/seng302/gameServer/ServerAdvertiser.java

@@ -6,20 +6,45 @@ import java.io.IOException;
 import java.net.InetAddress;
 import java.util.Hashtable;
 
+/**
+ * Advertises the game server on the local network
+ */
 public class ServerAdvertiser {
+    /*
+    Our service name & protocol
+
+    This must be in the format _Service._Proto.Name as per http://www.ietf.org/rfc/rfc2782.txt
+    Where Service is unique on the network, and protocol is usually _tcp.
+
+    The pseudo-domain 'local.' must end in a full-stop. This is used to indicate that
+    the lookup should be performed using an IP multicast query on the local IP network.
+
+    Read this before changing any of the following values
+    https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/NetServices/Articles/domainnames.html#//apple_ref/doc/uid/TP40002460-SW1
+     */
     private static String SERVICE = "_partyatsea";
     private static String PROTOCOL = "_tcp";
     public static String SERVICE_TYPE = SERVICE + "." + PROTOCOL + ".local.";
-    private static Integer PROTO_VERSION = 1;
-
 
     private static ServerAdvertiser instance = null;
     private static JmDNS jmdnsInstance = null;
+    private ServiceInfo serviceInfo; // Note: Whenever this is changed, our service will be re-registered on the network.
+
+    private Hashtable<String ,String> props;
 
     private ServerAdvertiser() throws IOException{
         jmdnsInstance = JmDNS.create(InetAddress.getLocalHost());
+
+        props = new Hashtable<>();
+        props.put("map", "");
+        props.put("spacesLeft", "0");
     }
 
+    /**
+     * Get an instance of the ServerAdvertiser, create an instance if there isn't already one
+     * @return A ServerAdvertiser Instance
+     * @throws IOException If there was an exception creating the instance
+     */
     public static ServerAdvertiser getInstance() throws IOException {
         if (instance == null){
             instance = new ServerAdvertiser();
@@ -28,13 +53,47 @@ public class ServerAdvertiser {
         return instance;
     }
 
-    public void registerGame(Integer portNo, String serverName, Integer spacesLeft, String mapName) {
-        Hashtable<String ,String> props = new Hashtable<>();
+    /**
+     * Set the map name & broadcast an update on the network
+     * @param mapName The new map name
+     * @return The current ServerAdvertiser instance
+     */
+    public ServerAdvertiser setMapName(String mapName){
+        props.replace("map", mapName);
 
-        props.put("map", mapName);
-        props.put("spacesLeft", spacesLeft.toString());
+        if (serviceInfo != null){
+            serviceInfo.setText(props);
+        }
 
-        ServiceInfo serviceInfo = ServiceInfo.create(SERVICE_TYPE, serverName, portNo, 0, 0, props);
+        return instance;
+    }
+
+    /**
+     * Set the spaces left on the server & broadcast an update on the network
+     * @param spacesLeft The number of spaces left on the server
+     * @return The current ServerAdvertiser instance
+     */
+    public ServerAdvertiser setSpacesLeft(Integer spacesLeft){
+        props.replace("spacesLeft", spacesLeft.toString());
+
+        if (serviceInfo != null){
+            serviceInfo.setText(props);
+        }
+
+        return instance;
+    }
+
+    /**
+     * Register this service on the network
+     *
+     * Note: other parameters (map name/spaces left etc) are set after the
+     * service has been registered
+     * @param portNo The servers port number
+     * @param serverName The servers name
+     */
+    public void registerGame(Integer portNo, String serverName) {
+
+        serviceInfo = ServiceInfo.create(SERVICE_TYPE, serverName, portNo, 0, 0, props);
 
         new java.util.Timer().schedule(
             new java.util.TimerTask() {
@@ -46,12 +105,14 @@ public class ServerAdvertiser {
                         System.out.println("Failed");
                     }
                 }
-            }, 0
-        );
+            }, 0);
     }
 
+    /**
+     * Unregister the service
+     */
     public void unregister(){
-        jmdnsInstance.unregisterAllServices();
-        jmdnsInstance = null;
+        if (serviceInfo != null)
+            jmdnsInstance.unregisterService(serviceInfo);
     }
 }