We Keep Coding

Using PythonAnywhere as a game server

I'm building a turn-based game and I'm hoping to implement client-server style networking. I really just need to send the position of a couple of objects and some other easily encodable data. I'm pretty new to networking, although I've coded some basic stuff in socket and twisted. Now, though, I need to be able to send the data to a computer that isn't on my local network, and I can't do port forwarding since I don't have admin access to the router and I'm also not totally sure that would do the trick anyways since I've never done it. So, I was thinking of running some Flask or Bottle or Django, etc. code off PythonAnywhere. The clients would then send data to the server code on PythonAnywhere, and when the turn passed, the other client would just go look up the information it needed on the server. I guess then the server would act as just a data bank with some simple getter and setter methods. My question is how can this be implemented? Can my Socket code on my client program talk to my Flask code on PythonAnywhere?

Yes, client code can talk to your project at PythonAnywhere, as you will be given a unique project url like http://yourblogname.pythonanywhere.com/. Your server will listen the 80 port at that url.

It depends what sort of connection your clients need to make to the server. PythonAnywhere supports WSGI, which means "normal" HTTP request/response interactions -- GET, POST, etc. That works well for "traditional" web pages or web apps.
If your client side needs dynamic, two-way connections using non-HTTP protocols, using raw sockets, or even websockets, PythonAnyhwere doesn't support that at present.

Client to Server Remote Function Calls in Python. How to implement?

I'm trying to set up a simple client to server interface for calling functions/programs on the server. A client will send a simple command to the server listening for such commands. Once the server receives a command from the client it will execute the following function or program on the server. I have looked into a simple TCP server receiving a text string and parsing that string then executing the a function or external program. I have read into using XML-RPC implemented with a twisted server as well.
What I'm asking is which would be the easiest to set up or are there any other ways to easily do this task?
Thanks.

There is a great tutorial for twisted that will do just fine as a teaching tool (and guide you by hand in writing a basic server/client services). Have a go at it http://twistedmatrix.com/documents/current/core/howto/tutorial/ what you will probably want to do is parse received info and act accordingly.

If it is appliable in your case, maybe you can use full-featured system for async/remote job execution like Celery?

There are more than one way to achieve your requirement ach with some pros and cons:
Python Low Level Sockets
Using Standard python socket libraries and cliet server architecture
Connecting to Server via protocols like Telnet/SSh and then triggering some code.
Using Python libraries like Telnet/ssh or Subprocess.
XML-RPC
Sending a XMP RPC request as described here http://docs.python.org/2/library/xmlrpclib.html
In my opinion easiest method to achieve remote method triggering is via Python Subprocess Module. I generally use following kind of syntax for my general purposes.
import subprocess
ret = subprocess.call(["ssh", "user#host", "program"]);
# or, with stderr:
prog = subprocess.Popen(["ssh", "user#host", "program"], stderr=subprocess.PIPE)
errdata = prog.communicate()[1]
Hope it helps

python tcp over http emulation

What's the easiest way to establish an emulated TCP connection over HTTP with python 2.7.x?
Server: a python program on pythonanywhere (or some analogue) free hosting, that doesn't provide a dedicated ip. Client: a python program on a Windows PC.
Connection is established via multiprocessing.BaseManager and works fine when testing both server and client on the same machine.
Is there a way to make this work over HTTP with minimal additions to the code?
P.S. I need this for a grid computing project.
P.P.S. I'm new to python & network & web programming, started studying it several days ago.
Found this: http://code.activestate.com/recipes/577643-transparent-http-tunnel-for-python-sockets-to-be-u/. Appears to be exactly what I need, though I don't understand how to invoke setup_http_proxy() on server/client side. Tried setup_http_proxy("my.proxy", 8080) on both sides, but it didn't work.
Also found this: http://docs.python.org/2/library/httplib.html. What does the HTTPConnection.set_tunnel method actually do? Can I use it to solve the problem in question?

Usage on the client:
setup_http_proxy("THE_ADRESS", THE_PORT_NUMBER) # address of the Proxy, port the Proxy is listening on
The code wraps sockets to perform an initial HTTP CONNECT request to the proxy setup to get an HTTP Proxy to proxy the TCP connection for you but for that you'll need a compliant proxy (most won't allow you to open TCP connections unless it's for HTTPS).
HTTPConnection.set_tunnel basically does the same thing.
For your use case, a program running on free hosting, this just won't work. Your free host probably will only allow you to handle http requests, not have long running processes listen for tcp connections(which the code assumes).
You should rethink your need to tunnel and organize your communication to post data (and poll for messages from the server, unless they're answers to the stuff you post). Or you can purchase a VPS hosting that will give you more control over what you can host remotely.

Callback Functions across computers?

I'm writing a python server/client app. If I serialize a function on the client and pass it to the server, can the server use it as a callback? I'm assuming there must be something extra I'd have to do as the client and server are communicating via packets, I just don't know what.
What I actually need is for the server to change one of the client's attributes (when the server is ready to accept another command), and I want an alternative to having the client continuously poll the server. Thanks for any help.

Take a look at Twisted JSON RPC.
A recent SO post: Python Twisted JSON RPC

Python, implementing proxy support for a socket based application (not urllib2)

I am little stumped: I have a simple messenger client program (pure python, sockets), and I wanted to add proxy support (http/s, socks), however I am a little confused on how to go about it. I am assuming that the connection on the socket level will be done to the proxy server, at which point the headers should contain a CONNECT + destination IP (of the chat server) and authentication, (if proxy requires so), however the rest is a little beyond me. How is the subsequent connection handled, specifically the reading/writing, etc...
Are there any guides on proxy support implementation for socket based (tcp) programming in Python?
Thank you

Maybe use something like SocksiPy which does all the protocol details for you and would let you connect through a SOCKS proxy as you would without it?

It is pretty simple - after you send the HTTP request: CONNECT example.com:1234 HTTP/1.0\r\nHost: example.com:1234\r\n<additional headers incl. authentication>\r\n\r\n, the server responds with HTTP/1.0 200 Connection established\r\n\r\n and then (after the double line ends) you can communicate just as you would communicate with example.com port 1234 without the proxy (as I understand you already have the client-server communication part done).

Have a look at stunnel.
Stunnel can allow you to secure
non-SSL aware daemons and protocols
(like POP, IMAP, LDAP, etc) by having
Stunnel provide the encryption,
requiring no changes to the daemon's
code