Today I was helping a customer connect from an original Microsoft Surface tablet running Surface RT to a remote Windows 7 desktop computer. The desktop uses a custom RDP listening port (e.g. 34111).
We encountered a problem with the standard Remote Desktop Connection application. According to the customer, when she typed “remote.domain.org:34111” as the Computer Name, she got a message that the colon was not allowed. But that is required to specify the custom port, so she couldn’t connect.
The workaround was to install the Remote Desktop application from the Windows Store, then run the Remote Desktop app (look for the orange icon) rather than the standard app. The UI is a bit different but it does accept the colon for specifying a port number.