I have a pretty simple use case where I want a websocket (or something like it) to send the contents of ZMQ pub/sub messages out to a browser in real time for an indefinite period of time. It's for personal use (home automation) so doesn't need to scale too much, but does need to be robust.

One-way communication (server to browser) is fine, but two ways would be nice, I guess. Not worried about two-way right now, since I can easily use HTTP(s) for browser-to-server.

I would like to use Mojolicious:: Lite (or something I can easily run in hypnotoad, and which allows for in-script hypnotoad configuration).

I found examples that look like they should work, but for me they don't - once the code hits the IO loop (whether the Mojo one or AnyEvent) to receive subscribed messages, I get either an 'operation on closed socket' if I'm using ZMQ::FFI, or a more cryptic error (something like Assertion failed: pfd.revents & POLLIN) if I use the ZMQ library like in the examples.

I decided to take a break and write the code in a plain perl script with Net::WebSocket::Server and AnyEvent, and found that it works fine when run from the command line: 

use strict;
use IO::Socket::SSL;
use ZMQ::FFI;
use ZMQ::FFI::Constants qw (ZMQ_SUB);
use AnyEvent;
use EV;

my $wsport = '3000';
my $zmqhost = 'tcp://localhost:5555';
my $subject = 'event';

Net::WebSocket::Server->new(
  listen => $wsport;
  on_connect => sub {
    my ($serv, $conn) = @_;
    $conn->on(
      ready => sub {
        my $context = ZMQ::FFI->new();
        my $subsocket = $context->socket(ZMQ_SUB);
        $subsocket->connect($zmqhost);
        $subsocket->subscribe($subject);
        my $fd = $subsocket->get_fd();
        my $w = AE::io $fd, 0, sub {
          while ($subsocket->has_pollin) {
            $conn->send_utf8($subsocket->recv());
          }
        };
        EV::run();
     },
    );
   },
  )->start;

[download]
which makes me think I should easily be able to make it work in Mojolicious::Lite, but for the life of me I can't seem to do it. It might be that in the code above, I'm able to put a subroutine in the on 'ready' state, but I can't figure out how to do that in the Mojolicious::Lite world.

(I would just use that code above, but it's single-user and not at all fault tolerant, and I'd rather not write a bunch of code to solve those issues if I don't have to)

Anyone with a suggestion on how to get this working in Mojolicious / hypnotoad, or perhaps another approach?

In reply to Mojolicious websocket question by antichef

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