Answer: Port 4950 is officially registered to the "Sybase Server Monitor" which is the SQL Anywhere Monitor that ships in the box with SQL Anywhere. If you're not already running the SQL Anywhere Monitor on that port, consider using 4950 for Foxhound.

Alternatively, consider using one of the "Dynamic and/or Private Ports" in the range 49152 through 65535.

See also...
How do I specify the HTTPS transport-layer security for Foxhound?
How do I tell Foxhound to use an HTTP port other than 80?
IANA port number assignments
Can't start HTTP listener on address 127.0.0.1:80
Could not bind to address ...
Database server shutdown due to startup error