[mythtv-users] Frontend can't connect to backend on system start

[Jim Carter]

On Wed, 18 Jul 2007, Michelle Dupuis wrote:

> By ssh'ing into the box, I see that the backend is in fact running, while
> the front end is complaining about can't connect.

The whole situation is weird, particularly that you can make it work by 
rebooting several times.  Here are some straws to grasp at:

A firewall normally is set to allow any connection from localhost, but a 
particularly aggressive one might be blocking your port.  Also if the 
frontend is told to connect to the FQDN of the machine (rather than to 
localhost), that counts as a connection from the network and would probably 
be blocked.  During boot the firewall should be started as one of the first 
steps, but if that's not true and if you're using parallel startups, random 
timing might let mythfrontend connect some times (before the firewall is 
engaged) and not others.  Try "iptables -t nat -L -v | more" and see if the 
firewall might be relevant.  This would be on port 6543.

Suppose the backend were sometimes not really listening on the port, or 
suppose there were two instances and the one that held the port were 
catatonic.  To detect this, do "fuser -v 6543/tcp", comparing a case when 
the frontend can connect, to one where it fails.  Sometimes fuser can't 
recognize a port user; also try "netstat -a -n | more" and look for 
something listening on 6543, as well as established connections on 6543 
(from the frontend).  A failure of these kinds would be really bizarre, and 
then you'd have the problem of what to do about it.

Hope this helps.  Good luck, you're going to need it.

James F. Carter          Voice 310 825 2897    FAX 310 206 6673
UCLA-Mathnet;  6115 MSA; 405 Hilgard Ave.; Los Angeles, CA, USA  90095-1555
Email: jimc at math.ucla.edu    http://www.math.ucla.edu/~jimc (q.v. for PGP key)