Using new `addConnection` which aims to be thread safe.

source/listeners/listener.d

@@ -79,7 +79,7 @@ public class BesterListener : Thread
 			besterConnection.start();
 
 			/* Add this client to the list of connected clients */
-			server.clients ~= besterConnection;
+			server.addConnection(besterConnection);
 		}
 
 		/* Close the socket */

source/server/server.d

@@ -103,6 +103,7 @@ public final class BesterServer
 		/**
 		* Append the connection to the array
 		*/
+		clients ~= connection;
 
 		/**
 		* Release the mutex so other listeners can now append