socket programming (client-server)

[ryan]

i have implemented a small client server model to do file transfer
over a LAN network.

It work with some machines on the network and on others it doesnt.
when i run the server.py file in some machine then it pops up a
windows security alert.

The message is as follows:

      Do you want to keep blocking this program?
there are three options below it. 1. Keep Blocking 2. Unblock 3. Ask
Me later.

I selected the option  unblock.Even then the client and server are not
able to communicate.
I get a error saying that:-

socket.error: (10060, 'Operation timed out')

I guess its a firewall problem... How do i go abt it?????
any help?