From: Lars Haugseth <ruby-talk@...>
Date: 2012-06-30T18:06:14+09:00
Subject: Re: Newb on String to Hex for UDP packet

On 06/29/2012 04:55 PM, ricky quirch wrote:
> Guys im a total newb to ruby and i have been battling with something
> that should be very simple, help!
>
> the situation is this: i need to feed a program via user input an int or
> worst case a hex string...
>
> eg: Please enter last octect of IP address: user enters:123 or 7B

How do you determine whether a given number (like 10) is hexadecimal or 
decimal without a prefix?

> i then want to include that as a hex byte in a UDP packet and send it.
>
> Eg: UDP = "/x00/x12/x23/(insert value in hex here)/x00/x00"
>
> I managed to include the value in there but the resulting UDP packet is
> sending the value in asccii,
> the packet looks like: 00:12:23:31:32:33:00:00

You need to use backslashes for character escapes in the string, not 
forward slashes.

   octet = 0x7b

   packet = "\x00\x12\x23#{octet.chr}\x00\x00"

   packet.bytes.to_a
   => [0, 18, 35, 123, 0, 0]

-- 
Lars Haugseth