BTW, I've found the commit which introduced the backsending mechanism to 
[netsend]:
https://github.com/pure-data/pure-data/commit/33627264be356096ff132272dbaaf7c5cdb44145#diff-92df49f719ba20e4c90e10e70c3d9154

before adding a socketreceiver to [netsend -u], the socket would never close (I 
just checked with Pd 0.46)! so although the current behaviour of closing the 
socket *could* be seen as a feature, it certainly has been a regression (as it 
must have broken existing setups). since your fix basically restores the old 
expected behaviour, I think it wouldn't need a flag, but that's just my two 
cents.

thanks for your work!

Christof

> Gesendet: Dienstag, 26. März 2019 um 03:13 Uhr
> Von: "Christof Ressi" <[email protected]>
> An: "Dan Wilcox" <[email protected]>
> Cc: pd-dev <[email protected]>
> Betreff: Re: [PD-dev] netsend/netreceive UDP ignore ECONNREFUSED
>
> nevermind, I've just seen that you've already implemented the fix by catching 
> ECONNREFUSED. the take away from my last e-mail is probably that the socket 
> receiver in [netsend -u] doesn't work, so that's something you can add to 
> your list :-D. in a few days I can help if needed, at the very least I can do 
> crossplatform testing.
> 
> > Gesendet: Dienstag, 26. März 2019 um 02:21 Uhr
> > Von: "Christof Ressi" <[email protected]>
> > An: "Dan Wilcox" <[email protected]>
> > Cc: pd-dev <[email protected]>
> > Betreff: Re: [PD-dev] netsend/netreceive UDP ignore ECONNREFUSED
> >
> > that's very strange as it shouldn't make any difference. what I *suspect* 
> > is really happening is that the socket isn't added to the readset in 
> > sys_domicrosleep and so the pollfunction (containing the call to recv) is 
> > never called. this is just a wild guess, though.
> > 
> > on the other hand, I couldn't test this quickly, as sending back to 
> > [netsend -u] seems to be broken anyway... I've tried with both providing 
> > the src port like [connect localhost 9999 9997( or getting the port number 
> > with [iemnet/udpreceive]. I even doesn't work when using another [netsend 
> > -u]...
> > 
> > actually, the easiest fix is to just suppress creating the right outlet (so 
> > no socketreceiver is created). it's a bit lazy, though :-) but it could 
> > mean something like: we just want to "broadcast" messages without any 
> > notion of "connection", therefore we don't need the right outlet either.
> > 
> > here's a prove of concept: 
> > https://github.com/Spacechild1/pure-data/tree/netsend-experiment
> > 
> > I've attached a patch to demonstrate the problem with sending to [netsend] 
> > and my lazy fix for [netsend].
> > 
> > Christof
> > 
> > 
> > Gesendet: Montag, 25. März 2019 um 23:03 Uhr
> > Von: "Dan Wilcox" <[email protected]>
> > An: "Christof Ressi" <[email protected]>
> > Cc: pd-dev <[email protected]>
> > Betreff: Re: [PD-dev] netsend/netreceive UDP ignore ECONNREFUSED
> > 
> > I did some quick hacking/testing and it seems that for UDP:
> >  
> > * not calling connect() in netsend_connect
> > * using sendto() with the server address struct in netsend_dosend
> > * & using recvfrom() instead of recv() in the socketreceiver
> >  
> > results in no "Connection refused" errors being thrown.
> > 
> >  
> > 
> > On Mar 25, 2019, at 11:32 AM, Christof Ressi 
> > <[email protected][mailto:[email protected]]> wrote: 
> > 
> > > For connectionless sending essentially, I think we would need to forego 
> > > the call to connect() in netsend_connect and keep a copy of the socket 
> > > address struct
> >  
> > IIUC, 'connect' on a UDP sockket does exactly that: it doesn't really 
> > "connect" to anything but just stores the default destination address, so 
> > 'connect' + 'send' is equivalent to 'sendto'.
> > at least that's how it has always worked for me.
> >  
> > http://man7.org/linux/man-pages/man2/connect.2.html[http://man7.org/linux/man-pages/man2/connect.2.html]
> >  
> > Christof
> >  
> > 
> > Gesendet: Montag, 25. März 2019 um 10:59 Uhr
> > Von: "Dan Wilcox" <[email protected][mailto:[email protected]]>
> > An: "Chris McCormick" <[email protected][mailto:[email protected]]>
> > Cc: pd-dev <[email protected][mailto:[email protected]]>
> > Betreff: Re: [PD-dev] netsend/netreceive UDP ignore ECONNREFUSED
> > 
> > Sure, however neither netsend nor udpsend work this way, so I was first 
> > trying to see what I could do without changing the internals a whole lot. 
> > It's definitely not "connectionless" when it keeps returning to a 
> > receiver...
> >  
> > For connectionless sending essentially, I think we would need to forego the 
> > call to connect() in netsend_connect and keep a copy of the socket address 
> > struct to use with sendto() instead of send() when actually sending. Since 
> > sendto() takes the address directly, it doesn't need a connect() ahead of 
> > time. Also, the UDP netsend / netreceive relay behavior could then use 
> > sendto() and recvfrom().
> >  
> > So conceptually, the current behavior of calling connect() for both UDP and 
> > TCP needs to change and I'd think then the the "connected" outlet for UDP 
> > simply means the socket is set up, but has no connotation for a current 
> > "connection." Again, I'm not sure how that would affect patches which would 
> > rely on the old behavior...
> >  
> > On Mar 25, 2019, at 3:42 AM, Chris McCormick 
> > <[email protected][mailto:[email protected]]> wrote: 
> > 
> > Hi Dan,
> > 
> > On 23/3/19 5:56 am, Dan Wilcox wrote:From my reading on the socket API, 
> > sending a UDP message conceptually shouldn't care about whether the 
> > receiver is there. However this is detected on a lower networking layer and 
> > propagated up to the application layer where it can be used or ignored.
> > You probably know this already but it is possible to operate UDP in 
> > connectionless or connection-oriented mode. Connection-oriented is 
> > somewhere between TCP and connectionless. In connection-oriented mode I 
> > suppose you would want to know if the other side is there or not, whereas 
> > with connectionless you probably just want to fire and forget. Not sure if 
> > this affects what you are doing but might help explain what you're seeing.
> > 
> > Cheers,
> > 
> > Chris.
> > 
> > --
> > https://mccormick.cx/[https://mccormick.cx/]
> > 
> > My tech development newsletter:
> > https://mccormick.cx/subscribe[https://mccormick.cx/subscribe] 
> > 
> > --------
> > Dan Wilcox
> > @danomatika[http://twitter.com/danomatika]
> > danomatika.com[http://danomatika.com/]
> > robotcowboy.com[http://robotcowboy.com/]
> >  _______________________________________________ Pd-dev mailing list 
> > [email protected][mailto:[email protected]] 
> > https://lists.puredata.info/listinfo/pd-dev 
> > 
> > --------
> > Dan Wilcox
> > @danomatika[http://twitter.com/danomatika]
> > danomatika.com[http://danomatika.com]
> > robotcowboy.com[http://robotcowboy.com]
> >  _______________________________________________
> > Pd-dev mailing list
> > [email protected]
> > https://lists.puredata.info/listinfo/pd-dev
> >
> 
> 
> 
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