{\r
                                        case 'c':\r
                                                TELNETServerApp_DisplayTCPConnections();\r
-                                               break;                                  \r
+                                               break;\r
+                                       default:\r
+                                               strcpy(AppData, "Invalid Command.\r\n");\r
+                                               uip_send(AppData, strlen(AppData));\r
+                                               break;\r
                                }\r
 \r
                                AppState->TELNETServer.NextState = TELNET_STATE_SendMenu;\r