[tpm] UDP broadcast/receive problems

[James E Keenan]

On 10/9/20 9:42 PM, Fulko Hew wrote:
> 
> 
> On Fri, Oct 9, 2020 at 9:06 PM James E Keenan <jkeenan at pobox.com 
> <mailto:jkeenan at pobox.com>> wrote:
> 
>     On 10/9/20 8:41 PM, Fulko Hew wrote:
>      > I'm trying to accomplish what I thought was easy, and yet I can't
>     get it
>      > to work.
>      >
>      > I have a number of devices that listen on UDP port 9999.
>      > So I want to send a broadcast message to my network and see all
>      > of their specific responses, so I can collect the list of IP
>     addresses
>      > (for subsequent messaging).
>      > For a single device, it looks like this:
>      >
>      > 192.168.1.149:port  --> 255.255.255.255:9999
>     <http://255.255.255.255:9999> <http://255.255.255.255:9999>
>      > 192.168.1.149:port  <-- 192.168.1.130:9999
>     <http://192.168.1.130:9999> <http://192.168.1.130:9999>
>      >
>      > So I've tried a number of things starting from a single socket
>     all the
>      > way to
>      > a send socket and a second receive socket, but I can never read the
>      > response that's sent.
>      >
>      > My last attempt is this code snippet... can anyone tell me what's
>     wrong ?
>      >
>      >
>      > $out = IO::Socket::INET->new(
>      >      PeerPort  => 9999,
>      >      PeerAddr  => inet_ntoa(INADDR_BROADCAST),
>      >      Proto     => udp,
>      >      ReuseAddr => 1,
>      >      Broadcast => 1)
>      >          or die "Can't bind : $@\n";
>      >
>      > my $lport = $out->sockport();           # get the local port that
>     was
>      > assigned
>      > print "sending from $lport\n";
>      >
>      > $in = IO::Socket::INET->new(
>      >      PeerPort  => 9999,
>      >      LocalPort => $lport,
>      >      Proto     => udp,
>      >      ReuseAddr => 1)
>      >          or die "Can't bind : $@\n";
>      >
>      > my $s = IO::Select->new($in);
>      > $s->add($out);
>      >
>      > $out->send('hello') or die "send: $!";
>      >
>      > while ($i++ < 100) {

In the line above, are you trying to say, "do this 100 times"?

>      >      my @ready = $s->can_read(1);
>      >      foreach (@ready) {
>      >          die("readable but nothing read\n") unless
>      > defined($_->recv($rsp, 1024));

What is $_ in the line above?

>      >          print $rsp;
>      >      }
>      > }
>      >
> 
>     First suggestion:  use strict;
> 
> 
> OK, I added strict.  It didn't tell me anything I didn't already know.
> 
>     In particular, I can't tell what you mean by $rsp
> 
> 
> $rsp is the receive buffer that'll contain each response to my broadcast.
> 
>