mssqlconn using port AND instance

[echi]

Hello Forum,

in all my connection strings to mssql databases there is
host.domain\instance,port

The manual says that with TMSSQLConnection the Hostname property can be either
host.domain\instance
or
host.domain:port

But the Database Server wants me to connect with instance AND port.
I tried
host.domain\instance:port
or
host.domain:port\instance
None of them was working.

How does this work with TMSSQLConnection or is this simply not supported?