sp_who in SQL 2008 uses a system view in the resource database so I think you will need to write your own version of sp_who or search for one that meets your needs. There are quite a few available that use the DMVs and you would be able to easily add the port to any of them.
"There are two ways of constructing a software design. One way is to make it so simple that there are obviously no deficiencies. And the other way is to make it so complicated that there are no obvious deficiencies."
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