# Industrial Network 2 writeup# Our problem in short: 
Master req. = 09 0F 00 00 00 05 01 1F 2F 38- Change slave id to 04- Set first output to high (1) and remaining to low (0)- The answer is not in the regular flag format (Uppercase hex with space delimeter between bytes)
# Let's begin!
So first of all I used https://www.modbustools.com/modbus.htmlas a reference for protocol format
Format tells us important info about frame:
09 - **Slave id**
0F - **Write multiple coils function**
00 00 - **Offset of first slave**
00 05 - **How many coils we wanna write**
01 - **Size of our data**
1F - **0 0 0 1 1 1 1 1 in binary which means all coils we wanted to write are set to high**
2F 38 - **CRC checksum**
Problem tells us to change slave id to 04 so:
**09** -> **04**
And first output to high (1) and remaining to low (0) so:
**1F [0 0 0 1 1 1 1 1]** -> **01 [0 0 0 0 0 0 0 1]**
And recalculated crc like this:
**2F 38** -> **6E A9**
So finally we have this request:
04 - **Slave id**
0F - **Write multiple coils function**
00 00 - **Offset of first slave**
00 05 - **How many coils we wanna write**
01 - **Size of our data**
01 - **0 0 0 0 0 0 0 1 setting first output to high and rest to low**
6E A9 - **crc**
Submit `04 0F 00 00 00 05 01 01 6E A9` and get your points now!