I've encountered that error at least twice and was twice stumped by it.

You're launching an asynchronous connection, but never launch the IO loop driving everything. Add this at the bottom of your script:

Mojo::IOLoop->start unless Mojo::IOLoop->is_running;
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Hey Corion that does it! Thank you.

edit: ouch i did not RTFM Mojo::UserAgent

It really depends on your needs. I'm mostly used to the server side of things writing cyclic executives, so i'm not sure what event based options for clients are available ;-)

The couple of times i needed a websocket client, i did it "by hand" using Protocol::WebSocket::Frame after connecting via IO::Socket::SSL, because that works well enough for my own cyclic needs.

Connection is easy, unless the W3C has re-defined things yet again. Here's an untested(!) minimal cyclic executive (a "worker") based on some of my existing codebase. I didn't include all that much error handling here, though, to keep the code small.

use IO::Socket::SSL;
use Protocol::WebSocket::Frame;
use Carp;
use Time::HiRes qw(sleep);
use Data::Dumper;

# Connect to server
my $sock = IO::Socket::SSL->new(
                PeerHost => $self->{server},
                PeerPort => $self->{port},
                SSL_verify_mode => SSL_VERIFY_NONE,
            ) or croak($!);

binmode($sock);

# Switch to unblocking after the SSL initiation
$sock->blocking(0);

# Write the header
my $header =
    "GET /public/api/blablabla HTTP/1.1\r\n" .
    "Host: example.com\r\n" .
    "Upgrade: websocket\r\n" .
    "Connection: Upgrade\r\n" .
    "Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==\r\n" .
    "Sec-WebSocket-Protocol: chat\r\n" .
    "Sec-WebSocket-Version: 13\r\n" .
    "Origin: https://cavac.at\r\n" .
    "\r\n";

$syswrite($sock, $header);

# "Parse" the return headers from the server by just skipping over it,
+ hoping for the best ;-)
syswrite($sock, $header);
my $line = "";
while(1) {
    my $char;
    sysread($sock, $char, 1);
    if(defined($char) && length($char)) {
        if($char eq "\r") {
            next;
        } elsif($char eq "\n") {
            if($line eq "") {
                # end of header
                last;
            } else {
                $line = "";
            }
        } else {
            $line .= $char;
        }
    } else {
        sleep(0.05); # wait a few microseconds for more data
    }
}

# Initiate the websocket frame handler
my $frame = Protocol::WebSocket::Frame->new(max_payload_size => 500 * 
+1024 * 1024, masked => 1);

# Send a frame
{
    my %request = (
        'request-type'  => 'HelloWorld',
        'message-id' => 'rand' . int(rand(1_000_000)),
        'other-stuff' => 'Hello Welt!',
    );
    my $outframe = $frame->new(buffer => encode_json(\%request), type 
+=> 'text', masked => 1)->to_bytes;
    syswrite($sock, $outframe);
}

# Handle messages from server
while(1) {
    # Read from socket and append data to the frame parser
    my $workCount = 0;
    while(1) {
        my $char;
        sysread($sock, $data, 1_000);
        last if(!defined($data) || !length($data));
        $frame->append($data);
        $workCount++;
    }

    # Parse and react to messages from server
    while(my $data = $frame->next_bytes) {
        my $msg = decode_json($data);
        print Dumper($msg); # Just print it out
    }

    if(1) { # Other cyclic work you need to do in the program
        # doSomeStuff();
        # $workCount++;

    }

    if(!$workCount) {
        # Nothing happened, just sleep a bit, try again later. Save on
+ CPU cycles
        sleep(0.05);
    }
}
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Hope that helps.

cavac thank you for this code. I think I will continue with a high-level module though since Corion solved my problem above, i will continue with that. thank you.