[Python-Dev] Non-blocking sockets, asynchronous connects and select.select. (original) (raw)

Alan Kennedy python-dev at alan.kennedy.name
Tue Mar 20 01:26:07 CET 2007

Dear all,

I'm working on a select implementation for jython (in combination with non-blocking sockets), and a set of unit tests for same.

I decided to run all of the non-blocking unit tests, both server and client side, in the same thread; seems to be a reasonable thing to do. After all, avoiding threads is one of the great benefits of non-blocking sockets.

Also, I'm writing the tests so that they'll hopefully pass on both cpython and jython.

But I'm getting behaviour I don't expect on cpython, when a non-blocking accept and connect_ex is used, for the server and client sides respectively.

The following piece of code outputs what I expect on my jython implementation, which is that both the server accept and client write calls would NOT block.

But when I run the code on cpython, the code reports that both calls would block, i.e. that neither side of the socket will progress with the connection.

The code is

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

import socket import select

SERVER_ADDRESS = ("", 54321)

server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server_socket.setblocking(0) server_socket.bind(SERVER_ADDRESS) server_socket.listen(5)

client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM) client_socket.setblocking(0)

result = client_socket.connect_ex(SERVER_ADDRESS)

rfds, wfds, xfds = select.select([server_socket], [client_socket], [], 1) if server_socket in rfds: print "Server socket: accept would not block" else: print "Server socket: accept would block" if client_socket in wfds: print "Client socket: write would not block" else: print "Client socket: write would block"

server_socket.close() client_socket.close()

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Is there some call that I am missing, e.g. something along the lines of the java finishConnect() method on SocketChannel?

http://java.sun.com/j2se/1.4.2/docs/api/java/nio/channels/SocketChannel.html#finishConnect()

Is there any way to make the above code report, on cpython, that neither side of the socket would block?

Am I missing some essential method call that would make either side progress to a connected socket?

Thanks,

Alan.

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