Why is my Icecast relay of a web radio station not working?

I try to relaying my favorite radio station using Icecast in my network. I’ve got a hint from the Icecast developer Marvin Scholz for a configuation that should work, but it doesn’t.

The URL of the radio station (mp3 stream) is https://stream.radio1.ch/128k (it’s https, port 443), here his configuration:

<relay>
    <server>stream.radio1.ch</server>
    <port>443</port> <!-- he proposed 80, but this works definitively not -->
    <mount>/128k</mount>
    <local-mount>/test</local-mount>
    <relay-shoutcast-metadata>1</relay-shoutcast-metadata>
</relay>

The error log-file (log-level 4) says the follwing:

[2025-11-29  18:34:25] INFO main/main Icecast 2.4.4 server started
[2025-11-29  18:34:25] DBUG yp/yp_recheck_config Updating YP configuration
[2025-11-29  18:34:25] INFO yp/yp_update_thread YP update thread started
[2025-11-29  18:34:25] INFO connection/get_ssl_certificate No SSL capability on any configured ports
[2025-11-29  18:34:26] DBUG slave/_slave_thread checking master stream list
[2025-11-29  18:34:26] DBUG slave/check_relay_stream Adding relay source at mountpoint "/stream"
[2025-11-29  18:34:26] INFO slave/start_relay_stream Starting relayed source at mountpoint "/stream"
[2025-11-29  18:34:26] INFO slave/open_relay_connection connecting to stream.radio1.ch:443
[2025-11-29  18:34:26] WARN slave/open_relay_connection Failed to connect to stream.radio1.ch:443
[2025-11-29  18:34:26] DBUG source/source_clear_source clearing source "/stream"
[2025-11-29  18:34:27] DBUG slave/check_relay_stream waiting for relay thread for "/stream"

And here my Icecast.xml configuration file

<icecast>
    <location>home</location>
    <admin>icemaster@localhost</admin>

    <limits>
        <clients>100</clients>
        <sources>2</sources>
        <queue-size>524288</queue-size>
        <client-timeout>30</client-timeout>
        <header-timeout>15</header-timeout>
        <source-timeout>10</source-timeout>
        <burst-on-connect>1</burst-on-connect>
        <burst-size>65535</burst-size>
    </limits>

    <authentication>
        <source-password>one4you</source-password>
        <relay-password>one4you</relay-password>
        <admin-user>admin</admin-user>
        <admin-password>comanche</admin-password>
    </authentication>
    <hostname>linux</hostname>

    <http-headers>
        <header name="Access-Control-Allow-Origin" value="*" />
    </http-headers>

    <relay>
        <server>stream.radio1.ch</server>
        <port>443</port>
        <mount>/stream</mount>
        <local-mount>/test</local-mount>
        <on-demand>0</on-demand>
        <relay-shoutcast-metadata>1</relay-shoutcast-metadata>
    </relay>

    <fileserve>1</fileserve>

    <paths>
        <basedir>/usr/share/icecast</basedir>
        <logdir>/var/log/icecast</logdir>
        <webroot>/usr/share/icecast/web</webroot>
        <adminroot>/usr/share/icecast/admin</adminroot>
        <pidfile>/var/run/icecast.pid</pidfile>
        <alias source="/" destination="/status.xsl"/>
    </paths>

    <logging>
        <accesslog>access.log</accesslog>
        <errorlog>error.log</errorlog>
        <loglevel>4</loglevel> <!-- 4 Debug, 3 Info, 2 Warn, 1 Error -->
        <logsize>10000</logsize> <!-- Max size of a logfile -->
    </logging>

    <security>
        <chroot>0</chroot>
        <changeowner>
            <user>icecast</user>
            <group>icecast</group>
        </changeowner>
    </security>
</icecast>