How do I link an outside server to MS SQL 2005 server?

I have been working on our SQL server for quite some time. I am in a bump in the road and would appreciate any help that anyone would be willing to offer. I have a production MIS system that runs on an IBM box and has AIX version: 05.03.0008.0000 TCP/IP as the base operating system. I am trying to transfer/link data from the AIX to the SQL server 2005. I know that I have to use a .dll but am stumped as to which one I should use. I want the data on SQL to be able to update as clients enter data into the AIX server. Does anyone have any suggestions or comments? If i didn’t provide enough info and you need more to help I would be more than willing to elaborate more on any information you need. Thanks a bunch.
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