Symptoms

Parallels RAS Gateway Agent showing "Port mismatch" status in RAS Console.

Cause

The following services could start listening to ports 80 or 443 before the RAS SecureClientGateway service:

• Web Deployment Agent Service
• SQL Server Reporting services
• IIS
• World Wide Web Publishing service
• IIS Admin Service
• RD Gateway Service
• KDC Proxy Server Service (KPS) is enabled.

Resolution1

Find which service is using port 80/443 using "netstat" command.

Stop the service that is listening to port 80/443 if it is not needed or change its configuration to listen to a different port so that RAS Gateway could work correctly.

For IIS, instructions are present here: https://stackoverflow.com/questions/19312136/how-do-i-change-iis-express-8-port-80-to-8080

Resolution2

Change the RAS Gateway port for TLS/SSL connections from 80/443 to some other available port.

Reference

How to determine what services are running under a SVCHOST.EXE process

View the List of Services Hosted by the svchost.exe Process in Windows

Windows Server 2012 - No response for request to KDC Proxy Server.