[Tutor] socket.recvfrom() not getting data

[gc]

I've hit the wall trying to receive some data from a socket and hope 
potential cross posting won't upset too many of you. In summary, I'm 
playing with a DHCP client written in python just to get a feel for it 
before getting down to serious work (see the PS for more info)

This segment of code sends a packet, using tcpdump i can see a response 
  coming from server running on another PC but i never see any data back 
from socket.recvfrom() - it just blocks:

<snip>
sock = socket.socket( socket.AF_INET, socket.SOCK_DGRAM )
sock.bind( (socket.gethostname(), CLI_PORT) )
sock.setsockopt( socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
cSent  = sock.sendto( data, 0, ( '<broadcast>', SRV_PORT ) )
print 'sent: ', cSent, ', from', sock.getsockname()
print 'status:', sock.getsockopt( socket.SOL_SOCKET, socket.SO_ERROR )
(rcvd, add) = sock.recvfrom( 512 )
print 'Got', len( rcvd ), 'bytes back'
<snip>


netstat tells me that the socket is still there - as long as the script 
is running. BTW the script runs with root privileges - the ports used 
are 67 and 68. The server response that i see with tcpdump looks 
healthy. My suspicion is that the protocol stack never passes the packet 
up to the socket but don't know why (the normal DHCP client daemon isn't 
running on this machine).

Is there a way to turn on some debugging with sockets?
Calling sock.setsockopt( socket.SOL_SOCKET, socket.SO_DEBUG, 1) didn't 
do much for me.

Any pointers appreciated.
TIA



PS
For the curious, the DHCP client is really meant to be implemented in 
C/C++ on a networked embedded device (needless to say, running a 
proprietary OS); there'll be lots of them and configuring IP address, 
netmask, gateway etc manually is a pain. So the python code is just a 
proof of concept.