[PD] ugly "already connected" errors

[Roman Haefeli]

What you found, challenged my understanding of UDP and it seems,
depending on implementation, the sender socket is in some cases
notified about the termination of the receiving socket. 

When I connect [netsend -u] to a small python script that opens a
listening socket, i can kill the script and start it again and [netsend
-u] can still send packets. When I connect to 'nc -v -u -l -p 11579'
instead, [netsend -b] can send packets only as long as the process is
running. When I kill nc and start it again, no messages reach their
destination anymore. I have to 'disconnect' and 'connect'. 

So what kind of software is opening the listening socket on the phone? 

Roman

On Fri, 2019-01-25 at 15:14 +0100, Roman Haefeli wrote:
> On Fri, 2019-01-25 at 15:01 +0100, michael strohmann wrote:
> > thanks for the answer!
> > but, 
> > in order to show that there is a connection betwenn the app to pd i
> > do:
> > 
> > [metro 1000]
> > > 
> > 
> > [toggle(					
> > > 
> > 
> > [oscformat BlinkingButton/value]
> > > 
> > 
> > [list prepend send]
> > > 
> > 
> > [list trim]
> > >    \
> > > 	[t b]
> > > 	|
> > > 	[disconnect, connect 192.168.178.189 8000(
> > >    /
> > 
> > [netsend -u -b] 
> > 
> > now everytime the phone is not available i get:
> > recv: Connection refused (111)
> > netsend: Bad file descriptor (9)
> > warning: 35 removed from poll list but not found
> > 
> > if i dont disconnect before sending i get the “already connected”
> > error.
> > and if i only connect once and leave the pd side connected, no
> > messages are received on the phone once it leaves the wlan.
> > 
> > messages sent from the phone are almost always received.
> > 
> > in any case it get a console message, either “connecting to port
> > 8000” or “already connected”
> > 
> > i am just concerned because my patch crashes or freezes or create
> > glitchy digital artefacts from time to time, and since it is a 24/7
> > audio installation i would like it to work.
> > how to find these bugs...
> 
> Oh, I see. That's much messier than I thought. I always believed an
> UDP
> socket stays open regardless of the presence of the other end. But
> seems to be not fully true. I'm not sure what's going on but it looks
> like the OS closes the socket without [netsend] actually noticing
> it. 
> 
> I would try what Antoine suggested and send a 'disconnect' each time
> before you connect again. There should be no harm in 'disconnect'ing
> and 'connect'ing many times.
> 
> Roman
> 
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