public void stopClients() {
   if (outputClient != null) {
     try {
       outputClient.stop();
     } catch (Exception e) {
     }
   }
   if (inputClient != null) {
     try {
       inputClient.stop();
     } catch (Exception e) {
     }
   }
 }
 public void stopOutputClient() throws Exception {
   if (outputClient != null) {
     outputClient.stop();
     outputClient.join();
   }
 }