Question

I need to do what most packet monitoring programs do (Wireshark, tcpdump, etc.). When data is received through Winsock, I just need to convert the packet to a hex representation and save it to file.

The data is just a simple char array.

I’ve tried lots of things like sprintf but with no luck. I also don’t want to use itoa since it’s not standard C from what I’ve learned.

Example:

If the packet contains “test”, then it should be dumped to file as “74 65 73 74”.

I can do all of the file handling stuff, and the Winsock code is working, I guess I just need to write a function to convert a char array to a hex representation, and I can’t seem to get it.

Answer 1

Perhaps you should show what you have tried since printf() and its variants is by far the simplest solution.

int emit_hex( FILE* file, const char* data, size_t len )
{
    int length = 0 ;
    size_t i ;

    for( i = 0; i < len; i++ )
    {
        length += fprintf( file, "%2.2X", (unsigned)pkt[i] ) ;
        if( i < len - 1)
        {
            length += fprintf( " " ) ;
        }
    }

    return length ;
}