Yaz, BizTalk could certainly do this using a suitable adapter. There are some sample TCP/IP Socket adapters out there, and you could take one of those and modify it so that it works according to your protocol. I'd start here: http://www.codeplex.com/Wiki/View.aspx?ProjectName=BTSTCPIP
There are also some other sample TCP/IP adapters on the user samples section on gotdotnet.