There is a serial device connected to physical serial port of the remote PC. You need to communicate with the device using a serial application running on your local PC.
A copy of Network Serial Port Kit is installed on the remote PC. It's used to share physical serial port to which the device is connected.
Another copy of Network Serial Port Kit is installed on the local PC. By means of it virtual serial port is created and connected to the physical serial port of the remote computer over network.

Now you can use your serial application on the local PC to communicate with remote serial device via virtual serial port.
You have serial communications software installed on different PCs. And there is no possibility to connect these PCs directly using RS-232 null-modem cable (no available serial ports or long distance between PCs). But both PCs are connected to the local network.
Using Network Serial Port Kit on each PC you can create pair of virtual serial ports and connect those virtual ports over network.
Data written to virtual serial port by application on one PC can be read by application on another PC and vice versa.

Serial communications application opens virtual serial port like usual physical one. And that's why you don't have to change your communications software.
As you know the software solutions are more cost effective than hardware solutions.
Network Serial Port Kit performs the same function as a hardware serial device server except it is a software program that runs on a Windows based computer and uses PC's serial ports.
Network Serial Port Kit converts usual computer to multi-port serial device server. Number of serial devices is limited by number of available COM ports only.

Serial Device Server is a hardware device that connects any serial devices (POS terminal, barcode scanner, weight scale, LED display, tunnel scanner, credit card reader, PBX, UPS etc.) to a network and provides an I/O path to serial device over TCP/IP network.
Because Network Serial Port Kit can do its job in the background, you still have a PC that you can use for other tasks.
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CA, UNITED STATES
Virtual Serial Port Kit 5.0.5 has been released. The program installer is available as MSI. Developer API is significantly improved.
April 2, 2008USB for Remote Desktop 1.0.2 has been released. Issue with workstation side freezing is fixed.
March 24, 2008USB over Network 3.3.10 and USB for Remote Desktop 1.0.1 have been released. Issue with accessing USB mass storage devices on 64bit server is fixed. Thanks to reporters for spotting the issue.
March 11, 2008USB over Network 3.3.9 has been released. Issue with sharing USB devices on Windows Vista is fixed.
March 6, 2008This happened! New product USB for Remote Desktop 1.0 has been released. Access your local USB devices in Terminal Server environment.
Network serial ports look and work like real hardware ports.
Network Serial Port Kit is compatible with Windows Vista™.