sending binary data over sockets

[thorley at gmail.com]

Greetings, since there was no reponse to my previous post about an
existing FastCGI server in python, I've taken to writing my own. (which
of course I'll share--*if* there's something to share ;)

My problem now, is that I need to send certain binary data over a
socket. That is, I want to make some bytes, and stuff them in a TCP
packet, send them down the pipe, and then listen for a response.

socket.send, as best I can tell, will only send strings. I've read on
the list other conversations where the recommendation was to use xdrlib
or struct. But it appears that is only useful when you control the
client and the server. PLEASE correct me if I'm wrong, but using struct
just encodes the binary data as a string, right?

# Example sending binary data as a string
s = socket.socket()
s.connect(("127.0.0.1", 8000))
packet = struct.pack('4B', 1, 2, 3, 4)
s.send(packet)

In my understaing the above just sends the string '\x01\x02\x03\x04',
not raw binary data. I've looked at Billy the Kid and pcap, which are
cool but not what I need.

Do I have to build my own packets from scratch and encode all the
TCP/IP headers myself to get this to work?

Solutions and Corrections welcome and appreciated.
Thanks very much

--
matthew