Create a pack in python to network send to C

Question

First of all, I'm very newbie in python, I've readed python documentation and I still don't understand how to that.

So, I need to send that structure: UDP_PAQUET:

 unsigned char type
 char ext[5]
 char data[50]

I tried to do this:

UDP_PKT = pack('BC5C50',"0x00", "2501", "user05")

but I'm getting a:

bad char in stuct format

Could someone help me a little?

Thanks!

Answer 1

First, there's no uppercase C format specifier in the struct module.

After that, I think that you want to use the s specifier for the ext and data members, and not pass in that first 0x00 value as a string, like:

UDP_PKT = pack('B5s50s', 0x00, "2501", "user05")

(Note that the size/repeat count appears before the format specifier.)

...which generates a packed string like:

'\x002501\x00user05\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'