make sure player names do not cause players to get disconnected

src/main/java/carpet/commands/PlayerCommand.java

@@ -272,7 +272,7 @@ public class PlayerCommand
         }
         catch (CommandSyntaxException ignored) {}
         String playerName = StringArgumentType.getString(context, "player");
-        if (playerName.length()>40)
+        if (playerName.length()>maxPlayerLength(source.getMinecraftServer()))
         {
             Messenger.m(context.getSource(), "rb Player name: "+playerName+" is too long");
             return 0;
@@ -294,6 +294,11 @@ public class PlayerCommand
         return 1;
     }
 
+    private static int maxPlayerLength(MinecraftServer server)
+    {
+        return server.getServerPort() >= 0 ? 16 : 40;
+    }
+
     private static int stop(CommandContext<ServerCommandSource> context)
     {
         if (cantManipulate(context)) return 0;