HW VSP3 is a software driver that adds a virtual serial port that adds a virtual serial port (e.g. COM5) to the operating system. This port redirects the data via a TCP/IP network to another hardware interface, which is specified by its IP address and port number. HW VSP3 is an updated version of HW VSP that adds support of NT Services and Windows Vista.
Single is free version, supports various devices, but only one serial port.