Websocket Input PlugIn TIBCO Mashery Connection::ConnectRefused

[Loris (Loris De Bellis)]

Hi all,
I wanted to create a Logstash pipeline that uses the websocket input plugin to connects to a TIBCO Mashery websocket.
I tried with the following, very simple, pipeline configuration:

input {
	 websocket {
       id => "ws"
       url => "wss://logstream-api.mashery.com/ecls/subscribe/***/***?key=***"
       type => "string"
       mode => "client"
   }
}

filter {}

output {
	stdout {}
}

When I run Logstash with this pipeline I get the following output:

[2020-04-21T08:50:36,324][WARN ][logstash.inputs.websocket][main] websocket input client threw exception, restarting {:exception=>#<FTW::Connection::ConnectRefused: logstream-api.mashery.com[34.232.148.67]:80>

We tried to contact the websocket and got a reply, so it seems the problem is Logstash.
The version used is 7.6.2.

Thank you
Loris