code: public int checkAck(InputStream in) throws IOException {
          int b = in.read();
          // b may be 0 for success,
          //          1 for error,
          //          2 for fatal error,
          //          -1
          if (b == 0) {
              return b;
          }
          if (b == -1) {
              return b;
          }
  
          if (b == 1 || b == 2) {
              StringBuffer sb = new StringBuffer();
              int c;
              do {
                  c = in.read();
                  sb.append((char) c);
              }
              while (c != '\n');
              if (b == 1) { // error
                  logger.error("Error checkACK: {}", sb.toString());
              }
              if (b == 2) { // fatal error
                  logger.error("Error checkACK: {}", sb.toString());
              }
          }
          return b;
      }
docs: UTILS