Fix some assorted stuff.

src/main/java/com/velocitypowered/proxy/connection/backend/PlaySessionHandler.java

@@ -5,6 +5,7 @@ import com.velocitypowered.proxy.protocol.packets.Disconnect;
 import com.velocitypowered.proxy.protocol.packets.JoinGame;
 import com.velocitypowered.proxy.protocol.packets.Ping;
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
+import com.velocitypowered.proxy.protocol.packets.Respawn;
 import io.netty.buffer.ByteBuf;
 import net.kyori.text.TextComponent;
 import net.kyori.text.format.TextColor;
@@ -36,6 +37,12 @@ public class PlaySessionHandler implements MinecraftSessionHandler {
             com.velocitypowered.proxy.connection.client.PlaySessionHandler playerHandler =
                     (com.velocitypowered.proxy.connection.client.PlaySessionHandler) connection.getProxyPlayer().getConnection().getSessionHandler();
             playerHandler.handleBackendJoinGame((JoinGame) packet);
+        } else if (packet instanceof Respawn) {
+            // Record the dimension switch, and then forward the packet on.
+            com.velocitypowered.proxy.connection.client.PlaySessionHandler playerHandler =
+                    (com.velocitypowered.proxy.connection.client.PlaySessionHandler) connection.getProxyPlayer().getConnection().getSessionHandler();
+            playerHandler.setCurrentDimension(((Respawn) packet).getDimension());
+            connection.getProxyPlayer().getConnection().write(packet);
         } else {
             // Just forward the packet on. We don't have anything to handle at this time.
             connection.getProxyPlayer().getConnection().write(packet);

src/main/java/com/velocitypowered/proxy/connection/backend/ServerConnection.java

@@ -60,7 +60,8 @@ public class ServerConnection {
         // Velocity doesn't yet support online-mode, unfortunately. That will come soon.
         return serverInfo.getAddress().getHostString() + "\0" +
                 proxyPlayer.getRemoteAddress().getHostString() + "\0" +
-                UuidUtils.toUndashed(proxyPlayer.getUniqueId());
+                UuidUtils.toUndashed(proxyPlayer.getUniqueId()) + "\0" +
+                "[]";
     }
 
     private void startHandshake() {

src/main/java/com/velocitypowered/proxy/connection/client/PlaySessionHandler.java

@@ -47,7 +47,7 @@ public class PlaySessionHandler implements MinecraftSessionHandler {
         if (packet instanceof Ping) {
             Ping ping = (Ping) packet;
             if (ping.getRandomId() != lastPing) {
-//                throw new IllegalStateException("Client sent invalid ping; expected " + lastPing + ", got " + ping.getRandomId());
+                throw new IllegalStateException("Client sent invalid ping; expected " + lastPing + ", got " + ping.getRandomId());
             }
 
             // Do not forward the packet to the player's server, because we handle pings for all servers already.
@@ -102,4 +102,8 @@ public class PlaySessionHandler implements MinecraftSessionHandler {
             currentDimension = joinGame.getDimension();
         }
     }
+
+    public void setCurrentDimension(int currentDimension) {
+        this.currentDimension = currentDimension;
+    }
 }