Creating Custom UDP Packet

Question

I am trying to interface with my internet connected gas fire. The manufacturer has told me that I can communicate with it on UDP port 3300.

He says I can send the packet with the information "SEARCH_FOR_FIRES" to the local subnet address to receive a response.

The packets should be composed in 15 bytes, as follows:

Byte 1: StartByte(0x47 'G') Byte 2: Command ID Byte 3: DataSize Byte 4-13: Data Byte 15: CRC Byte 15: End Byte (0x46 'F')

They give, 0x473100000000000000000000003146 as am example. 31 is the command ID for the "SEARCH_FOR_FIRES" command.

The only problem is I have no idea how to create these packets... I'm using the Windows verson of Packet Sender and it gives me the option of inputting ASCII or HEX values. So far I have:

HEX: 47 31 00 03 01 46 ASCII: G1\00\03\01F

But none of them seem to work, but I don't know how to find the HEX equivalent of 0x473100000000000000000000003146.

Can someone help?

I've been using the program Packet Sender. I'm not sure how to summarise the command, but I've tried sending HEX 47 31 00 03 01 46 to 192.168.1.76 (the IP of the fire). As far as I see, that emulates the example they provided (0x473100000000000000000000003146) — JWinstanley
– JWinstanley, Commented Dec 10, 2016 at 10:57

nnovich-OK · Accepted Answer · 2016-12-27 22:54:41Z

1

Well, that sounds weird, but hex equivalent of 0x473100000000000000000000003146 is... 0x473100000000000000000000003146 itself :) "0x" stands for hex representation, it's followed by hex numbers, so you need to pass "47 31 00 00 00 00 00 00 00 00 00 00 00 31 46" to packet sender.

By the way, do you know what to expect from device on successful packet sending? Should device perform some noticeable indication of processing "SEARCH_FOR_FIRES" command? It's possible, that device will silently send some report in UDP packet back to you, so you may need to setup network capturing (e.g. wireshark) to see and analyze response.

answered Dec 27, 2016 at 22:54

nnovich-OK

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2 Comments

nnovich-OK Over a year ago

Played a bit more with packet sender. It seems to display replies, so you should be fine without wireshark.

JWinstanley Over a year ago

Thanks :) The 0x through me off, but I've got this working now and receive the expected reply.

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