This challenge provides a jpg file and a pklg file. The jpg is shown a part of string on LEGO EV3 device. Length of the string, I guess, might be **58**. EV3 is supported USB or Bluetooth connection. Bluetooth connection is hinted in the pklg file opened with Wireshark. Transmission is worked between two **RFCOMM** protocol entities. There are two types in all  RFCOMM packages. Much attention should be focused on **Sent**, while the **Rcvd** packages are both same like each other. 
There are three different length of packages: **32, 33, 34**. After analysising, I notice three key position, shown below (I called them in turn as: **Order in group, Group number, Data**):
![](https://img2018.cnblogs.com/blog/908031/201810/908031-20181022112309293-1629771090.jpg)
![](https://img2018.cnblogs.com/blog/908031/201810/908031-20181022112320517-1937176487.jpg)
![](https://img2018.cnblogs.com/blog/908031/201810/908031-20181022112330114-323771902.jpg)
if length == 32: 
          Order in group        0x81  Group number  0x84  Dataif length == 33: 
    0x81  Order in group        0x81  Group number  0x84  Dataif length == 34: 
    0x82  Order in group  0x00  0x81  Group number  0x84  Data
Sort them by Group number at first. If equal, sorted by Order in group.
    h,0a 28 68    i,14 28 69    t,1e 28 74    c,28 28 63    o,32 28 6f    n,3c 28 6e    {,46 28 7b    m,50 28 6d    ......
**hitcon{m1nd5t0rm_communication_and_firmware_developer_kit}**