A blog by Devendra Tewari
Virtual serial ports are a convenient way to test software that accesses hardware over serial ports, particularly when that hardware is not available yet. They can also be useful for logging and tracing purposes.
I maintain a simple tool that allows me to open serial ports, and send and receive data. It is developed using C# and works reasonably well on Linux with Mono. That is the tool I used to test the different redirectors described below.
Free Virtual Serial Ports
Free Virtual Serial Ports version 2.11 by HHD Software works on Windows, right up to version 8.1 64-bit. It is easy to create two bridged serial ports, where data sent to one port arrives at the other and vice-versa. I also love Free Hex Editor Neo by HHD Software.
HW VSP3
HW VSP3 version 3.1.2 does serial to TCP redirection. It requires a TCP server at the other end. One way to set that up is to use ncat utility that accompanies NMAP. I have had the need to play with TCP so often, I have rolled my own little tool.
I found that HW VSP3 sends additional data when a connection is established. It also tended to corrupt data during large transfers. It works all right for small controlled tests.
Commercial options
Commercial options that are popular are Virtual Serial Port Driver by Eltima, and Virtual Serial Port Kit by FabulaTech.