$99.95 - WCSC (Willies Computer Software Co)

Professional serial communication library - DLL for Windows & MSDOS libraries. Supports ZModem, YModem, XModem file transfer protocols, modems, Microsoft Visual C/ C++, Borland C/ C++, Access, Visual Basic, QuickBasic, & all tools that can cal
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Free - AGG Software

COM Port Data Emulator is a unique tool that will be a great asset in the arsenal of any developer working with serial interfaces. It was created for emulating a COM or Ethernet device, generating a stream of data and sending it to a specific port.
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$29.95 - Haxxio

Replace serial (RS232, RS485) cables with ethernet network, using UDP. Most uses for the Redirector are based on one of replacing a simple serial cable, or connecting serial devices over WiFi links, or enabling groups op PCs to communicate together.
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Free - EnTech Taiwan

TVicPort is set of general purpose device drivers that allow you to access and control hardware directly from within a Win32 application without using the Windows DDK.
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