[Python-Dev] socket.create_connection slow

[Michael Foord]

Victor Stinner wrote:
> Hi,
>
> Le Wednesday 14 January 2009 12:23:46 Kristján Valur Jónsson, vous avez 
> écrit :
>   
>> socket.create_connection() trying to connect to ("localhost", port)
>> (...) 
>> return an AF_INET6 entry before the AF_INET one and try connection 
>> to that. This connect() attemt fails after approximately one second, 
>> after which we proceed to do an immediately successful connect() call 
>> to the AF_INET address.
>>     
>
> This is the normal behaviour of dual stack (IPv4+IPv6): IPv6 is tried before 
> IPv4. SocketServer uses AF_INET by default, so the "IPv6 port" is closed on 
> your host. Why does it take so long to try to connect to the IPv6 port? On 
> Linux, it's immediate:
> ----
> $ time nc6 ::1 8080
> nc6: unable to connect to address ::1, service 8080
>
> real    0m0.023s
> user    0m0.000s
> sys     0m0.008s
> ----
>
> On my host (Ubuntu Gutsy), "localhost" name has only an IPv4 address. The 
> address "::1" is "ip6-localhost" or "ip6-loopback".
>
> You should check why the connect() to IPv6 is so long to raise an error. About 
> the test: since SocketServer address family is constant (IPv4), you can force 
> IPv4 for the client.
>
>   
This is something of a bugbear on Vista in general. Doing local 
web-development with localhost can be really painful until you realise 
that switching to 127.0.0.1 solves the problem...

Michael