[Haskell-cafe] Issue with "connectTo" function in "network" package

aditya siram aditya.siram at gmail.com
Fri Jun 4 14:52:08 EDT 2010

Here's my GHCI session (with my network card off):
Prelude Network Network.Socket> connectTo "localhost" (PortNumber 3000)
*** Exception: connect: does not exist (Connection refused)
Prelude Network Network.Socket> connectTo "" (PortNumber 3000)
{handle: <socket: 7>}

The OS is Ubuntu (Lucid) Linux. The contents of "/etc/hosts" and
"/etc/nsswitch.conf" are:

> cat /etc/nsswitch.conf
# /etc/nsswitch.conf
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.

passwd:         compat
group:          compat
shadow:         compat

hosts:          files mdns4_minimal [NOTFOUND=return] dns mdns4
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

> cat /etc/hosts       localhost       deech-mac-ubuntu

# The following lines are desirable for IPv6 capable hosts
::1     localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts


On 6/4/10, Roman Cheplyaka <roma at ro-che.info> wrote:
> * aditya siram <aditya.siram at gmail.com> [2010-06-03 22:30:33-0500]
>> Hi all,
>> I had an issue where using the connectTo [1] function would fail to
>> connect to "localhost" if my wireless card was turned off. The moment
>> I turned on my wireless connection it worked. But if I use connectTo
>> with "" [2] with my network off it works.
>> I confirmed that "localhost' resolves to "" by pinging
>> "localhost" from command line with the Internet off.
>> Is this a bug in "connectTo"?
>> -deech
>> [1] connectTo "localhost" (PortNumber some_number)
>> [2] connectTo "" (PortNumber some_number)
> How exactly did it fail? Did it throw an exception? If so, what was the
> exception?
> Which operating system did you observe that under?
> If that was Linux, can you show the contents of the following files on
> that system:
> /etc/nsswitch.conf
> /etc/hosts
> --
> Roman I. Cheplyaka :: http://ro-che.info/
> "Don't let school get in the way of your education." - Mark Twain
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