Robert J.Berger <rberger@ibd.com> reported this on the gpsd-dev mailing list of the GPSD project.

"Until I changed the line in /etc/hosts from:

::1    localhost.localdomain   localhost

to:

127.0.0.1       localhost.localdomain   localhost

the gps.py [library distributed by the GPSD project] would fail when trying to open the socket connection to gpsd:

   File "/usr/local/bin/spGps.py", line 198, in __init__
     self.connect(host, port)
   File "/usr/local/bin/spGps.py", line 237, in connect
     raise socket.error, msg
socket.error: (111, 'Connection refused')

This is with Python 2.4.4 under Red Hat Linux, kernel version not reported.

Robert believes, and I concur, that this is not a GPSD bug.  Rather, something lower-level -- possibly the Python socket library, possibly some C library it uses -- is having indigestion on the IPV6 notation.

Berger reports the kernel is 2.6.18.  Fedora Core 6.

Can you please report the values of "host" and "port" when that error is raised?

host is 'localhost'
port is 2947

What's going on here is that gps.py is a Python client module for a local daemon that monitors GPS devices on the host's serial and USB ports and presents output on port 2947.  While it is possible to use gps.py to monitor a remote host, Berger wasn't doing that. The socket module threw an error while attempting to connect to localhost.

This seems to work fine for me:

>>> s = socket.socket(socket.AF_INET6)
>>> s.bind(('ip6-localhost', 8091))
>>> s.getsockname()
('::1', 8091, 0, 0)
>>> 

exarkun@charm:~$ grep ip6-localhost /etc/hosts
::1 ip6-localhost ip6-loopback
exarkun@charm:~$ 

Are you sure this isn't a local misconfiguration?  Perhaps gpsd isn't listening on ::1, only 127.1?

>Are you sure this isn't a local misconfiguration?

I'm not.  I didn't see it happen. I suggest you email Mr. Berger and ask him.

I will try to get a simple example that reproduces it. Unfortunately I don't have access to the system that was doing it today. I will try to get something in the bug report in the next day or so.

But basically if /etc/hosts had localhost defined as ::1 the connect method failded, when I set localhost to 127.0.0.1 the connect worked.

Other non-python (c++) processes were able to access the socket when localhost was set to ::1

This was on Fedora Core 6 with the latest patches at that time.

I believe this is a local configuration error, and possibly a C library error.

I'll attach two programs: g.c does what I believe gpsd does, and c.py 
does what I believe spGps.py does.

This works fine on my system after I change localhost to be ::1 in /etc/hosts,
even though g.c only listens on IPv4 interfaces. On my system, it "works" because
libc (getaddrinfo) then goes to DNS, and my DNS server has an entry for localhost.

If C programs work on the machine, it may be because they use gethostbyname,
not getaddrinfo.

Closing as "works for me".
File Added: g.c

File Added: c.py