mapping lpt1 in RDP session

Hi,

I have an application running on our RD server which requires printing to LPT1.  I have few clients with locally attached printer connecting to the server through RDP. My problem is the lpt mapping doesn't seem to work within the RD session.

If the client is in the same LAN as the RDP server, I can use net use lpt1 \\rdp_client_name\print_share to map the locally attached printer successfully within the RDP session. However, if the client is connecting the server from a remote site, the same command will produce the following error, I tried different UNC path such as \\tsclient\prn#, \\tsclient\print_share and \\rdp_client_name\print_share and it has the same error. Any idea? Thanks

system error 1200 has occured
the specified device name is invalid