How to end TCP socket data while using readline()?

[Cameron Simpson]

On 26Feb2010 10:39, Arjun <arjun.chennu at gmail.com> wrote:
| Hi, I have a small script that runs a TCP server. A client connects to
| this server and transmits a stored file line-by-line, and then waits
| for a confirmation "done". However, when I run them the first loop
| never really ends -- as the TCP server keeps expecting more data. I am
| using a file-like-object, and so somehow I have to communicate to the
| server that it is the end-of-file.
| 
| here is some server code
| <snip>
|             sock1.bind(('', port))
|             print "Listening at port: ", port
|             sock1.listen(1)      # listening socket
|             (conn, addr) = sock1.accept()    # connected socket
|             print 'Client (localhost) port: ', addr[1]
| 
|             cf = conn.makefile('r',0)    # file like obj for socket
[...]
|         print 'close'
|         cf.flush()
|         cf.close()
|         sfp.close()
[...]

Too many files. It's not that hard! Or shouldn't be.

| So what I am wondering is:
| 
| 1. Using a file-like object means that the socket becomes uni-
| directional, until the mode of the file object is changed from 'r' to
| 'w' (or vice versa). This seems inefficient, and rather unPythonesque.
| Can somebody tell me if there is a more elegant way of receiving all
| the lines from the client, and then sending a "done" message to the
| client?

Get the socket. It is a file descriptor (or in may be a python "socket"
object with a file descriptor inside).

Open _two_ "file" objects on it using
  from_file = os.fdopen(fd_of_socket, "r")
  to_file = os.fdopen(fd_of_socket, "w").

Use the same:
  print >>to_file, 'close'
  to_file.flush()
method as you're using already.
Read from to_file as needed.

The same scheme should work in both server and client:

Don't look for EOF, watch the input line flow.

You might need to use readline() instead of the file-by-line iteration stuff,
which I seem to recall has some sort of problem handing out the "latest"
line.

Cheers,
-- 
Cameron Simpson <cs at zip.com.au> DoD#743
http://www.cskk.ezoshosting.com/cs/

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        - Barry Sheene