/**
   * 从网络字节流中读取2个字节拼装成为short
   * 
   * @param from
   * @param fromIndex
   * @return
   */
  public static short getShortData(byte[] from, int fromIndex) {
   if (from == null) {
    return 0;
   }
   int ch1 = from[fromIndex] & 0xff;
   int ch2 = from[fromIndex + 1] & 0xff;  return (short) ((ch1 << 8) + (ch2 << 0));
  }