I've just checked MX200 with software TC6.2 and do not see any process which might listen port 857/UDP.
I'd recommend you check endpoint to make sure that NMAP is telling truth. Log into endpoint using ssh and root credentials. The following command will show you if some process is listening to specific port:
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.