client.pl

use Mojo::Base -base;
use 5.20.0;

use Mojo::UserAgent;

my $ua = Mojo::UserAgent->new;
$ua->websocket("ws://localhost:3000/code.json" => sub {
  my ($ua, $tx) = @_;
  return unless $tx->is_websocket;

  $tx->on(finish => sub {
      my ($tx, $code, $reason) = @_;
      say "WebSocket closed with status $code.";
  });

  $tx->on(message => sub {
      my ($tx, $msg) = @_;
      say "WebSocket message: $msg";
  }); 

  $tx->send({json => {msg => "Hello"}});
});

Mojo::IOLoop->start;

server.pl

use Mojolicious::Lite;
use 5.20.0;
use experimental 'signatures';

websocket '/code.json' => sub ($c) {
    $c->app->log->debug('WebSocket opened');
    $c->inactivity_timeout(300);

    $c->on(message => sub ($c, $msg) {
        $c->app->log->debug("msg: $msg");
    });

    $c->on(json => sub ($tx, $hash) {
        $c->app->log->debug("WebSocket message via JSON: $$hash{msg}");
    });

    $c->on(finish => sub ($c, $code) {
        $c->app->log->debug("WebSocket closed with status $code");
    });

};

app->start;