MSIR.0573 SSL client trying to use unsupported protocol: (protocol)
A client (probably a web browser) tried to connect to an SSL port but tried to use an SSL protocol that is explicitly blocked by the SSLPROT parameter in the JANUS DEFINE command for the port being connected to. Note that setting SSLPROT to 2 will, somewhat counter-intuitively, prevent access to the port with SSL V2.
Either eliminate the SSLPROT parameter from the port definition, set it to allow the excluded protocol, set up an SSLPROTOCOLERR handler, or upgrade the browser to support the excluded protocol.