Great! If there is a wiki or FAQ page for networking with Haskell it might be worth updating. -deech On 6/4/10, Roman Cheplyaka wrote:

/etc/hosts is the file responsible for resolving 'localhost' hostname. As you can see from it, there are two entries for localhost: one contains IPv4 address (127.0.0.1) and another contains IPv6 address (::1).

The behaviour you observe is kinda bug in connectTo function. Instead of trying all of the addresses, this function just tries the first one. Until it is fixed (I'm gonna write and send a patch soon), can you live with this temporary hack? If for some reason the answer is "no", you have to use low-level functions from Network.Socket module for now.

* aditya siram [2010-06-04 14:15:47-0500]

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Doing (1) solves my problem. What did I do and why did it work? Thanks a lot for your help! -deech

On 6/4/10, Roman Cheplyaka wrote:

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Confirm if any of the following solves the problem:

1. commenting out (by prepending putting hash sign '#' in the beginning of the line) the following line in /etc/hosts:

::1 localhost ip6-localhost ip6-loopback

2. executing as root the following command:

rmmod ipv6

* aditya siram [2010-06-04 13:51:29-0500]

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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 "127.0.0.1" (PortNumber 3000) {handle: }

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 127.0.0.1 localhost 127.0.1.1 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

-deech

On 6/4/10, Roman Cheplyaka wrote:

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* aditya siram [2010-06-03 22:30:33-0500]

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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 "127.0.0.1" [2] with my network off it works.

I confirmed that "localhost' resolves to "127.0.0.1" 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 "127.0.0.1" (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 _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

-- Roman I. Cheplyaka :: http://ro-che.info/ "Don't let school get in the way of your education." - Mark Twain

-- Roman I. Cheplyaka :: http://ro-che.info/ "Don't let school get in the way of your education." - Mark Twain