Re: [rc-hackers] yarp connect is hanging in my scripts!

[Paul F. <pau...@li...>]

Quick follow up - it looks like Stefan's problem was an address 
conflict, with an "old" process lurking in the background and holding on 
to a socket.

This happens to people fairly often.  Some suggestions:

+ Check the value returned by [Buffered]Port.open().  If it is false, 
the port didn't open successfully.  Since it is easy to miss an "address 
conflict" warning in a pile of other messages, consider terminating the 
program if this happens.  That way, it'll be very obvious that there's a 
problem.  (I should update yarp write/rpc/read to do this...)

+ There's a page on our wiki on diagnosing and recovering from this problem:

  http://eris.liralab.it/wiki/Conflicts

Cheers,
Paul

Paul Fitzpatrick wrote:
> Stefán Freyr Stefánsson wrote:
>   
>> ...
>>
>> But every so often I end up hanging in the "yarp connect" part! This seems to 
>> happen more often when there's some extra load on my computer (for example I 
>> managed to "reproduce" the problem a few times by starting a movie, but this 
>> is one of those annoying "it doesn't happen every time" problems).
>>
>> So basically, I end up seeing the "both ports are ready, connecting..." line 
>> but then everything stops and I never see the "ports connected" line.
>>
>> Has anybody had this problem? Does anyone have a concrete way of making sure 
>> that the ports do get connected within scripts?
>>   
>>     
>
> Hi Stefan,
>
> I'd be interested to hear if anyone else has this problem.
>
> As a stopgap measure, you could use the "timeout" program, and do 
> something like:
>     timeout 5 yarp connect $1 $2 $PROTOCOL
> This would wait a maximum of 5 seconds for connection to occur. 
>
> If you have the CVS version of YARP, you can do:
>   while ! yarp exists $1 $2; do
>     timeout 5 yarp connect $1 $2 $PROTOCOL
>     if yarp exists $1 $2; then
>         echo "ports connected"
>     else
>         echo "ports failed to connect"
>     fi
>   done
>
> The two-argument "yarp exists" command checks for a connection between 
> the named ports.  This command hasn't made it into a formal release yet 
> (it got added during the RobotCub summer school in July).
>
> With the last formal release, you can grep through the output of a "yarp 
> ping" to see if a connection has been made.
>
> If you want to help figure out what the problem is, try running the 
> connect as follows (assuming Linux):
>   YARP_VERBOSE=1 yarp connect $1 $2 $PROTOCOL
> or
>    YARP_VERBOSE=1 timeout 5 yarp connect $1 $2 $PROTOCOL
>
> and send me the output upon failure.
>
> Cheers,
> Paul
>
>
>
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