Server discovery bug fixes & error handling improvements

- Fixed concurrency bug that prevented players from connecting to servers
- Discovery server can restart itself if it crashes
- Added nicer error handling for server discovery.
- Using AWS to get servers external IP address.

Tags: #story[1281]

src/main/java/seng302/App.java

@@ -80,6 +80,14 @@ public class App extends Application {
         ViewManager.getInstance().initialStartView(primaryStage);
     }
 
+    private static void runDiscoveryServer(){
+        try{
+            new DiscoveryServer();
+        }
+        catch (Exception e){
+            runDiscoveryServer();
+        }
+    }
 
     public static void main(String[] args) throws Exception {
         try {
@@ -92,7 +100,7 @@ public class App extends Application {
             launch(args);
         }
         else{
-            new DiscoveryServer();
+            runDiscoveryServer();
         }
     }
 }

src/main/java/seng302/discoveryServer/DiscoveryServerClient.java

@@ -2,15 +2,19 @@ package seng302.discoveryServer;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
+import seng302.discoveryServer.util.ServerListing;
+import seng302.discoveryServer.util.ServerRepoStreamParser;
 import seng302.gameServer.messages.Message;
 import seng302.gameServer.messages.RoomCodeRequest;
 import seng302.gameServer.messages.ServerRegistrationMessage;
 import seng302.model.stream.packets.PacketType;
-import seng302.discoveryServer.util.ServerListing;
-import seng302.discoveryServer.util.ServerRepoStreamParser;
+import seng302.visualiser.controllers.ViewManager;
 
+import java.io.BufferedReader;
 import java.io.IOException;
+import java.io.InputStreamReader;
 import java.net.Socket;
+import java.net.URL;
 import java.util.Timer;
 import java.util.TimerTask;
 
@@ -20,9 +24,28 @@ public class DiscoveryServerClient {
     private static String roomCode = null;
     private Timer serverListingUpdateTimer;
     private Logger logger = LoggerFactory.getLogger(DiscoveryServerClient.class);
+    private String ip = "";
+    private Boolean isInInvalidState = false;
 
     public DiscoveryServerClient() {
+        try {
+            ip = getInetIpAddr();
+        } catch (Exception e) {
+            failError();
+        }
+    }
 
+    public String getInetIp(){
+        return ip;
+    }
+
+    private void failError() {
+        isInInvalidState = true;
+        ViewManager.getInstance().showErrorSnackBar("You do not appear to be able to connect to the internet. Matchmaking will be unavailable.");
+    }
+
+    public boolean didFail(){
+        return isInInvalidState;
     }
 
     /**
@@ -30,6 +53,8 @@ public class DiscoveryServerClient {
      * @param serverListing The listing to register
      */
     public void register(ServerListing serverListing){
+        if (isInInvalidState) return;
+
         if (serverListingUpdateTimer != null){
             serverListingUpdateTimer.cancel();
             serverListingUpdateTimer = null;
@@ -53,7 +78,8 @@ public class DiscoveryServerClient {
      * Stop updating the server registration updates
      */
     public void unregister(){
-        serverListingUpdateTimer.cancel();
+        if (serverListingUpdateTimer != null)
+            serverListingUpdateTimer.cancel();
     }
 
     /**
@@ -143,5 +169,27 @@ public class DiscoveryServerClient {
     public static String getRoomCode(){
         return roomCode;
     }
+
+    public static String getInetIpAddr() throws Exception {
+        URL myIp = new URL("http://checkip.amazonaws.com");
+        BufferedReader in = null;
+        try {
+            in = new BufferedReader(new InputStreamReader(
+                    myIp.openStream()));
+            String ip = in.readLine();
+            return ip;
+        } finally {
+            if (in != null) {
+                try {
+                    in.close();
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+            }
+        }
+    }
+
+
+
 }
 

src/main/java/seng302/discoveryServer/util/ServerTable.java

@@ -48,7 +48,7 @@ public class ServerTable {
            updateTtlForServer(server);
            return;
         }
-        logger.debug("Added new server - " + server.getServerName());
+        logger.debug("Added new server - " + server.getServerName() + " at address: " + server.getAddress() + ":" + server.getPortNumber());
         servers.add(server);
     }
 

src/main/java/seng302/gameServer/MainServerThread.java

@@ -1,11 +1,5 @@
 package seng302.gameServer;
 
-import java.io.IOException;
-import java.net.ServerSocket;
-import java.util.ArrayList;
-import java.util.Random;
-import java.util.Timer;
-import java.util.TimerTask;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import seng302.gameServer.messages.Message;
@@ -18,6 +12,13 @@ import seng302.model.stream.xml.parser.RaceXMLData;
 import seng302.model.stream.xml.parser.RegattaXMLData;
 import seng302.utilities.GeoUtility;
 
+import java.io.IOException;
+import java.net.ServerSocket;
+import java.util.ArrayList;
+import java.util.Random;
+import java.util.Timer;
+import java.util.TimerTask;
+
 /**
  * A class describing the overall server, which creates and collects server threads for each client
  * Created by wmu16 on 13/07/17.
@@ -158,6 +159,8 @@ public class MainServerThread implements Runnable, ClientConnectionDelegate {
     }
 
     private void sendSetupMessages() {
+        MessageFactory.updateBoats(new ArrayList<>(GameState.getYachts().values()));
+
         broadcastMessage(MessageFactory.getRaceXML());
         broadcastMessage(MessageFactory.getRegattaXML());
         broadcastMessage(MessageFactory.getBoatXML());
@@ -253,16 +256,26 @@ public class MainServerThread implements Runnable, ClientConnectionDelegate {
                 }
             });
         } else {
-            serverToClientThread.addConnectionListener(this::sendSetupMessages);
-            MessageFactory.updateBoats(new ArrayList<>(GameState.getYachts().values()));
+            //serverToClientThread.addConnectionListener(this::sendSetupMessages);
         }
         serverToClientThreads.add(serverToClientThread);
-        serverToClientThread.addDisconnectListener(this::clientDisconnected);
+
         try {
             ServerAdvertiser.getInstance().setNumberOfPlayers(GameState.getNumberOfPlayers());
         } catch (IOException e) {
             logger.warn("Couldn't update advertisement");
         }
+
+        while (regattaXMLData == null && raceXMLData == null){
+            try {
+                Thread.sleep(50);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+
+        }
+        serverToClientThread.addConnectionListener(this::sendSetupMessages);
+        serverToClientThread.addDisconnectListener(this::clientDisconnected);
     }
 
     /**
@@ -283,6 +296,7 @@ public class MainServerThread implements Runnable, ClientConnectionDelegate {
                 serverToClientThread.sendSetupMessages();
             }
         }
+
         serverToClientThreads.remove(closedConnection);
 
         try {

src/main/java/seng302/gameServer/MessageFactory.java

@@ -1,18 +1,6 @@
 package seng302.gameServer;
 
-import java.util.ArrayList;
-import java.util.List;
-import seng302.gameServer.messages.BoatLocationMessage;
-import seng302.gameServer.messages.BoatSubMessage;
-import seng302.gameServer.messages.RaceStartNotificationType;
-import seng302.gameServer.messages.RaceStartStatusMessage;
-import seng302.gameServer.messages.RaceStatus;
-import seng302.gameServer.messages.RaceStatusMessage;
-import seng302.gameServer.messages.RaceType;
-import seng302.gameServer.messages.XMLMessage;
-import seng302.gameServer.messages.XMLMessageSubType;
-import seng302.gameServer.messages.YachtEventCodeMessage;
-import seng302.gameServer.messages.YachtEventType;
+import seng302.gameServer.messages.*;
 import seng302.model.Player;
 import seng302.model.ServerYacht;
 import seng302.model.stream.xml.generator.RaceXMLTemplate;
@@ -20,9 +8,11 @@ import seng302.model.stream.xml.generator.RegattaXMLTemplate;
 import seng302.model.stream.xml.parser.RaceXMLData;
 import seng302.model.stream.xml.parser.RegattaXMLData;
 import seng302.model.token.Token;
-import seng302.model.token.TokenType;
 import seng302.utilities.XMLGenerator;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /**
  * A Class for interfacing between the data we have in the GameState to the messages we need to send
  * through the MainServerThread.

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

@@ -1,7 +1,7 @@
 package seng302.gameServer;
 
-import seng302.discoveryServer.util.ServerListing;
 import seng302.discoveryServer.DiscoveryServerClient;
+import seng302.discoveryServer.util.ServerListing;
 
 import javax.jmdns.JmDNS;
 import javax.jmdns.ServiceInfo;
@@ -133,7 +133,7 @@ public class ServerAdvertiser {
                 }
             }, 0);
 
-        ServerListing serverListing = new ServerListing(serverName, props.get("map"), getLocalHostIp(), portNo, Integer.parseInt(props.get("capacity")));
+        ServerListing serverListing = new ServerListing(serverName, props.get("map"), new DiscoveryServerClient().getInetIp(), portNo, Integer.parseInt(props.get("capacity")));
         repositoryClient.register(serverListing);
     }
 

src/main/java/seng302/gameServer/ServerToClientThread.java

@@ -1,6 +1,21 @@
 package seng302.gameServer;
 
 
+import javafx.beans.property.SimpleObjectProperty;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import seng302.gameServer.messages.*;
+import seng302.model.Player;
+import seng302.model.ServerYacht;
+import seng302.model.stream.packets.PacketType;
+import seng302.model.stream.packets.StreamPacket;
+import seng302.model.stream.xml.parser.RaceXMLData;
+import seng302.model.stream.xml.parser.RegattaXMLData;
+import seng302.utilities.StreamParser;
+import seng302.utilities.XMLGenerator;
+import seng302.utilities.XMLParser;
+import seng302.visualiser.fxObjects.assets_3D.BoatMeshType;
+
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
@@ -12,26 +27,6 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.zip.CRC32;
 import java.util.zip.Checksum;
-import javafx.beans.property.SimpleObjectProperty;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import seng302.gameServer.messages.BoatAction;
-import seng302.gameServer.messages.ChatterMessage;
-import seng302.gameServer.messages.ClientType;
-import seng302.gameServer.messages.CustomizeRequestType;
-import seng302.gameServer.messages.Message;
-import seng302.gameServer.messages.RegistrationResponseMessage;
-import seng302.gameServer.messages.RegistrationResponseStatus;
-import seng302.model.Player;
-import seng302.model.ServerYacht;
-import seng302.model.stream.packets.PacketType;
-import seng302.model.stream.packets.StreamPacket;
-import seng302.model.stream.xml.parser.RaceXMLData;
-import seng302.model.stream.xml.parser.RegattaXMLData;
-import seng302.utilities.StreamParser;
-import seng302.utilities.XMLGenerator;
-import seng302.visualiser.fxObjects.assets_3D.BoatMeshType;
-import seng302.utilities.XMLParser;
 
 /**
  * A class describing a single connection to a Client for the purposes of sending and receiving on
@@ -196,6 +191,7 @@ public class ServerToClientThread implements Runnable {
                                 // TODO: 17/08/2017 ajm412: Send a response packet here, not really necessary until we do shapes.
                                 break;
                             case RACE_XML:
+                                System.out.println("Got raceXML from client");
                                 raceXMLProperty.set(
                                     XMLParser.parseRace(
                                         StreamParser.extractXmlMessage(packet)

src/main/java/seng302/visualiser/ClientToServerThread.java

@@ -1,36 +1,22 @@
 package seng302.visualiser;
 
+import javafx.util.Pair;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import seng302.gameServer.messages.*;
+import seng302.model.stream.packets.PacketType;
+import seng302.model.stream.packets.StreamPacket;
+import seng302.utilities.XMLParser;
+
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.net.Socket;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.List;
-import java.util.Queue;
-import java.util.Timer;
-import java.util.TimerTask;
+import java.util.*;
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.zip.CRC32;
 import java.util.zip.Checksum;
-import javafx.util.Pair;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-import seng302.gameServer.messages.BoatAction;
-import seng302.gameServer.messages.BoatActionMessage;
-import seng302.gameServer.messages.ChatterMessage;
-import seng302.gameServer.messages.ClientType;
-import seng302.gameServer.messages.CustomizeRequestMessage;
-import seng302.gameServer.messages.CustomizeRequestType;
-import seng302.gameServer.messages.Message;
-import seng302.gameServer.messages.RegistrationRequestMessage;
-import seng302.gameServer.messages.RegistrationResponseStatus;
-import seng302.gameServer.messages.XMLMessage;
-import seng302.gameServer.messages.XMLMessageSubType;
-import seng302.model.stream.packets.PacketType;
-import seng302.model.stream.packets.StreamPacket;
-import seng302.utilities.XMLParser;
 
 /**
  * A class describing a single connection to a Server for the purposes of sending and receiving on
@@ -137,8 +123,10 @@ public class ClientToServerThread implements Runnable {
                             else {
                                 if (clientId == -1) continue; // Do not continue if not registered
                                 streamPackets.add(new StreamPacket(type, payloadLength, timeStamp, payload));
-                                for (ClientSocketListener csl : listeners)
-                                    csl.newPacket();
+                                synchronized (this) {
+                                    for (ClientSocketListener csl : listeners)
+                                        csl.newPacket();
+                                }
                             }
                         }
                     } else {
@@ -322,7 +310,9 @@ public class ClientToServerThread implements Runnable {
     }
 
     public void addStreamObserver (ClientSocketListener streamListener) {
-        listeners.add(streamListener);
+        synchronized (this){
+            listeners.add(streamListener);
+        }
     }
 
     public void removeStreamObserver (ClientSocketListener streamListener) {
@@ -330,11 +320,15 @@ public class ClientToServerThread implements Runnable {
     }
 
     public void addDisconnectionListener (DisconnectedFromHostListener listener) {
-        disconnectionListeners.add(listener);
+        synchronized (this){
+            disconnectionListeners.add(listener);
+        }
     }
 
     public void removeDisconnectionListener (DisconnectedFromHostListener listener) {
-        disconnectionListeners.remove(listener);
+        synchronized (this){
+            disconnectionListeners.remove(listener);
+        }
     }
 
     private int readByte() throws ByteReadException {

src/main/java/seng302/visualiser/GameClient.java

@@ -1,15 +1,5 @@
 package seng302.visualiser;
 
-import java.io.IOException;
-import java.text.SimpleDateFormat;
-import java.time.ZoneId;
-import java.time.ZoneOffset;
-import java.util.ArrayList;
-import java.util.Collections;
-import java.util.Date;
-import java.util.List;
-import java.util.Map;
-import java.util.TimeZone;
 import javafx.application.Platform;
 import javafx.collections.FXCollections;
 import javafx.collections.ObservableList;
@@ -48,6 +38,12 @@ import seng302.visualiser.controllers.LobbyController;
 import seng302.visualiser.controllers.RaceViewController;
 import seng302.visualiser.controllers.ViewManager;
 
+import java.io.IOException;
+import java.text.SimpleDateFormat;
+import java.time.ZoneId;
+import java.time.ZoneOffset;
+import java.util.*;
+
 /**
  * This class is a client side instance of a yacht racing game in JavaFX. The game is instantiated
  * with a JavaFX Pane to insert itself into.
@@ -114,7 +110,7 @@ public class GameClient {
             this.lobbyController = ViewManager.getInstance().goToLobby(true);
 
         } catch (IOException ioe) {
-            showConnectionError("Unable to find server");
+            ViewManager.getInstance().showErrorSnackBar("Unable to find server");
         }
     }
 

src/main/java/seng302/visualiser/controllers/LobbyController.java

@@ -2,12 +2,6 @@ package seng302.visualiser.controllers;
 
 import com.jfoenix.controls.JFXButton;
 import com.jfoenix.controls.JFXDialog;
-import java.io.IOException;
-import java.net.URL;
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Map;
-import java.util.ResourceBundle;
 import javafx.application.Platform;
 import javafx.collections.ListChangeListener;
 import javafx.fxml.FXML;
@@ -19,6 +13,7 @@ import javafx.scene.layout.AnchorPane;
 import javafx.scene.layout.StackPane;
 import javafx.scene.layout.VBox;
 import javafx.scene.paint.Color;
+import seng302.discoveryServer.DiscoveryServerClient;
 import seng302.gameServer.GameStages;
 import seng302.gameServer.GameState;
 import seng302.model.ClientYacht;
@@ -28,12 +23,17 @@ import seng302.model.RaceState;
 import seng302.model.mark.CompoundMark;
 import seng302.model.mark.Corner;
 import seng302.model.stream.xml.parser.RaceXMLData;
-import seng302.discoveryServer.DiscoveryServerClient;
 import seng302.utilities.Sounds;
 import seng302.visualiser.MapPreview;
 import seng302.visualiser.controllers.cells.PlayerCell;
 import seng302.visualiser.controllers.dialogs.BoatCustomizeController;
-import seng302.visualiser.controllers.dialogs.DirectConnectController;
+
+import java.io.IOException;
+import java.net.URL;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.ResourceBundle;
 
 public class LobbyController implements Initializable {
 
@@ -91,6 +91,17 @@ public class LobbyController implements Initializable {
             serverName.setText(ViewManager.getInstance().getProperty("serverName"));
             mapName.setText(ViewManager.getInstance().getProperty("mapName"));
 
+            int tries = 0;
+
+            while (DiscoveryServerClient.getRoomCode() == null && tries <= 10){
+                try {
+                    Thread.sleep(10);
+                } catch (InterruptedException e) {
+                    e.printStackTrace();
+                }
+                tries ++;
+            }
+
             if (DiscoveryServerClient.getRoomCode() != null){
                 setRoomCode(DiscoveryServerClient.getRoomCode());
             }

src/main/java/seng302/visualiser/controllers/ServerListController.java

@@ -5,17 +5,11 @@ import com.jfoenix.controls.JFXDialog;
 import com.jfoenix.controls.JFXDialog.DialogTransition;
 import com.jfoenix.controls.JFXTextField;
 import com.jfoenix.validation.RequiredFieldValidator;
-import java.io.IOException;
-import java.net.URL;
-import java.util.Arrays;
-import java.util.List;
-import java.util.ResourceBundle;
 import javafx.application.Platform;
 import javafx.fxml.FXML;
 import javafx.fxml.FXMLLoader;
 import javafx.fxml.Initializable;
 import javafx.geometry.Pos;
-import javafx.scene.control.Alert;
 import javafx.scene.control.Label;
 import javafx.scene.control.ScrollPane;
 import javafx.scene.input.KeyCode;
@@ -23,19 +17,21 @@ import javafx.scene.layout.StackPane;
 import javafx.scene.layout.VBox;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-import seng302.discoveryServer.DiscoveryServer;
-import seng302.gameServer.ServerDescription;
-import seng302.discoveryServer.util.ServerListing;
 import seng302.discoveryServer.DiscoveryServerClient;
-import seng302.gameServer.messages.RoomCodeRequest;
+import seng302.discoveryServer.util.ServerListing;
+import seng302.gameServer.ServerDescription;
+import seng302.gameServer.messages.ServerRegistrationMessage;
 import seng302.utilities.Sounds;
 import seng302.visualiser.ServerListener;
 import seng302.visualiser.ServerListenerDelegate;
 import seng302.visualiser.controllers.cells.ServerCell;
 import seng302.visualiser.controllers.dialogs.DirectConnectController;
-import seng302.visualiser.validators.HostNameFieldValidator;
-import seng302.visualiser.validators.NumberRangeValidator;
-import seng302.visualiser.validators.ValidationTools;
+
+import java.io.IOException;
+import java.net.URL;
+import java.util.Arrays;
+import java.util.List;
+import java.util.ResourceBundle;
 
 public class ServerListController implements Initializable, ServerListenerDelegate {
 
@@ -90,6 +86,8 @@ public class ServerListController implements Initializable, ServerListenerDelega
             Sounds.playButtonClick();
         });
 
+        directConnectDialog = createDirectConnectDialog();
+
         for (JFXTextField textField : Arrays.asList(roomNumber)) {
             // Event for pressing enter to submit direct connection
             textField.setOnKeyPressed(event -> {
@@ -105,26 +103,26 @@ public class ServerListController implements Initializable, ServerListenerDelega
         }
 
         autoSelectGame.setOnMouseReleased(e -> {
-            try {
-                ServerListing listing = new DiscoveryServerClient().getRandomServer();
+            ServerListing listing;
+            DiscoveryServerClient client = new DiscoveryServerClient();
 
-                if (listing == null){
-                    Alert alert = new Alert(Alert.AlertType.ERROR);
-                    alert.setHeaderText("Error finding game");
-                    alert.setContentText("No servers are up");
-                    alert.showAndWait();
-                }
-                else{
-                    ViewManager.getInstance().getGameClient().runAsClient(listing.getAddress(), listing.getPortNumber());
-                }
+            try {
+                listing = client.getRandomServer();
             } catch (Exception e1) {
-                e1.printStackTrace();
-                logger.error("Error getting listing");
-                Alert alert = new Alert(Alert.AlertType.ERROR);
-                alert.setHeaderText("Error finding game");
-                alert.setContentText("Couldn't contact matchmaking server");
-                alert.showAndWait();
+                ViewManager.getInstance().showErrorSnackBar("Unable to connect to matchmaking server. Are you connected to the internet?");
+                return;
             }
+
+            if (client.didFail()){
+                return;
+            }
+
+            if (listing == null || listing.equals(ServerRegistrationMessage.getEmptyRegistration())) {
+                ViewManager.getInstance().showErrorSnackBar("There are currently no servers available for you to connect to.");
+                return;
+            }
+
+            ViewManager.getInstance().getGameClient().runAsClient(listing.getAddress(), listing.getPortNumber());
         });
 
         /*
@@ -186,9 +184,6 @@ public class ServerListController implements Initializable, ServerListenerDelega
                 e.printStackTrace();
                 logger.warn("Could not create Server Creation Dialog.");
             }
-
-            directConnectDialog = createDirectConnectDialog();
-
         });
     }
 
@@ -235,20 +230,30 @@ public class ServerListController implements Initializable, ServerListenerDelega
     }
 
     private void connectToRoomCode(String roomCode){
+        DiscoveryServerClient client = new DiscoveryServerClient();
+        ServerListing serverListing;
+
+        if (client.didFail()){
+            return;
+        }
+
+        try {
+            serverListing = client.getServerForRoomCode(roomCode);
+        } catch (Exception e) {
+            ViewManager.getInstance().showErrorSnackBar("Error connecting to matchmaking server. Please try again later.");
+            return;
+        }
+
+        if (serverListing == null || serverListing.equals(new ServerListing("","","", 0, 0))){
+            ViewManager.getInstance().showErrorSnackBar("No servers could be found with that room code.");
+            return;
+        }
+
         try {
-            ServerListing serverListing = new DiscoveryServerClient().getServerForRoomCode(roomCode);
             ViewManager.getInstance().getGameClient().runAsClient(serverListing.getAddress(), serverListing.getPortNumber());
         }
-        catch (java.net.ConnectException e){
-            //TODO Add proper dialog
-            logger.warn("Couldn't connect to discovery server");
-            Alert alert = new Alert(Alert.AlertType.ERROR);
-            alert.setHeaderText("Couldn't connect to discovery server");
-            alert.setContentText("Couldn't connect to " + DiscoveryServer.DISCOVERY_SERVER);
-            alert.showAndWait();
-        }
         catch (Exception e) {
-            logger.warn("Error discovering room code");
+            ViewManager.getInstance().showErrorSnackBar("Error connecting to matchmaking service.");
         }
     }
 

src/main/java/seng302/visualiser/controllers/ViewManager.java

@@ -6,16 +6,10 @@ import com.jfoenix.controls.JFXDialog;
 import com.jfoenix.controls.JFXDialog.DialogTransition;
 import com.jfoenix.controls.JFXSnackbar;
 import com.jfoenix.svg.SVGGlyph;
-import java.io.IOException;
-import java.util.HashMap;
 import javafx.application.Platform;
 import javafx.collections.ObservableList;
 import javafx.fxml.FXMLLoader;
-import javafx.scene.Cursor;
-import javafx.scene.Node;
-import javafx.scene.Parent;
-import javafx.scene.Scene;
-import javafx.scene.SceneAntialiasing;
+import javafx.scene.*;
 import javafx.scene.image.Image;
 import javafx.scene.layout.HBox;
 import javafx.scene.layout.StackPane;
@@ -28,6 +22,9 @@ import seng302.utilities.Sounds;
 import seng302.visualiser.GameClient;
 import seng302.visualiser.controllers.dialogs.KeyBindingDialogController;
 
+import java.io.IOException;
+import java.util.HashMap;
+
 public class ViewManager {
 
     private static ViewManager instance;
@@ -369,6 +366,14 @@ public class ViewManager {
         return loader.getController();
     }
 
+    public void showErrorSnackBar(String msg){
+        decorator.getStylesheets()
+                .add(getClass().getResource("/css/dialogs/Snackbar.css").toExternalForm());
+
+        JFXSnackbar bar = new JFXSnackbar(decorator);
+        bar.enqueue(new JFXSnackbar.SnackbarEvent(msg));
+    }
+
     public Stage getStage() {
         return stage;
     }