From: Eleanor McHugh <eleanor@...>
Date: 2009-03-01T04:12:14+09:00
Subject: Re: Gets the broadcast address of an IP address

On 28 Feb 2009, at 16:20, Sai Hl wrote:
> Hi Ruby communauty.  I am trying to broadcast a message using  
> UDPSocket
> on destination port 10000.  My code is:
>
> client = UDPSocket.new
> client.connect Socket.gethostname, 10000
> client.setsockopt(Socket::SOL_SOCKET, Socket::SO_BROADCAST, true)
> client.send data, 0
>
> But my packet is not a broadcast, its address is the same as my host:
> 192.168.0.101
>
> In order to do so on the external interface of my system (named  
> en0), I
> had remplaced this:
>  client.connect Socket.gethostname, 10000
> by this:
>  client.connect "192.168.0.255", 10000
>
> And now this is working.  But is there a way to get automatically the
> "192.168.0.255" address thanks to a Ruby method?  I know I can get  
> my IP
> with IPSocket.getaddress(Socket.gethostname) but I don't see any way  
> to
> gets its broadcast address.
>
> Thanks


The simplest way to do it is to use a regex to change the last term in  
the quad:

IPSocket.getaddress(Socket.gethostname).gsub!(/.\d{1,3}$/, '.255')


Ellie

Eleanor McHugh
Games With Brains
http://slides.games-with-brains.net
----
raise ArgumentError unless @reality.responds_to? :reason