Establishing a p2p connection in python

[gs]

Ville Vainio <ville at spammers.com> wrote in message news:<du71xg9f9vn.fsf at lehtori.cc.tut.fi>...
> >>>>> "gs" == gs  <gs.lists at gmail.com> writes:
> 
>     gs> Proposed solution: I thought that one approach could be to
>     gs> write a small server for my public server with the sole
>     gs> purpose of keeping track of connected users and establishing
>     gs> p2p connections on demand.
> 
> One lightweight approach (assuming that a web server is available)
> would be to put up a cgi script that adds the ip:port information to
> onlineusers.txt. Then the clients can just use urllib to notify the
> script when they become online, and also get the list of connected
> clients by just retrieving onlineusers.txt. Of course onlineusers.txt
> could contain the lists of shared files for each client as well...
> 
> If you use unique user ids, you can keep the file from growing up too
> much. If not, you could clean up dead clients by trying to connect all
> the specified addresses.
> 
>     gs> 1) I've written a threaded server that stores information
>     gs> about connected servers in a "container class". This class
>     gs> h

olds information about username, a unique ID, the connecting
>     gs> adress and the actual socket. I have not been able to find any
>     gs> information online on how i could go about to connect two
>     gs> sockets. It would seem like the socket is already "occupied"
>     gs> since it is connected to the server. Could one duplicate, or
>     gs> otherwise get a dedicated socket for sending binary data, to
>     gs> one connected socket from another? A few pointers and/or tips
>     gs> would be greatly appreciated!
> 
> If you went on to "connect" the two sockets, you would just
> instantiate a thread that forwards the data, and would use more server
> bandwidth than an FTP server would have used.
> 
> The idea in p2p is to make clients connect to each other. The task of
> the server is to tell the clients about other clients so they can
> connect to each other.
> 
> 
>     gs> 2) I've also failed to find python specific information on how
>     gs> abouts one would do file resuming. I would think that you,
>     gs> somehow, use md5-checksums to check file status and somehow
>     gs> skip the first part of the datastream. Also, pointers and
>     gs> maybe an explanation in (short) pseudo-code would be much
>     gs> appreciated.
> 
> It's trivial since you are going to implement a custom protocol
> anyway. Make the "get file" command that you pass to the file provider
> such that in addition to the file name you pass the starting offset
> within the file.
> 
> 
>     gs> 3) Is this too big of a project for a novice programmer such
>     gs> as myself? I do want to go through with this since it's a
>     gs> genuine problem, but i do not know if i'm ready. I'm not a
>     gs> "quitter" per say, but i'm afraid doing something TOO advanced
>     gs> in the beginning might be overwhelming :)
> 
> No, it's a great first project. Go ahead, I believe you will find it
> surprisingly easy, educational and something for which Python is a
> perfect fit.
> 
> It'll be a fun project to expand as well, to provide chunked file
> transfer etc. You could also explore the alternative of making it a
> bunch of wrapper scripts that just invoke bittorrent...

Thanks all of you for the nice feedback. I'm spending all of my
sparetime just reading up on all technlogies and suggestions! :)

cheers,
gs