I want to use serial port by several applications on a remote PC
Serial to Ethernet Connector will cope with this task easily. No other software is required except this one. To test its functionality download free trial version from: http://www.eltima.com/products/serial-over-ethernet/
Note: if you need to share serial port by several applications on the local PC you will need Serial Splitter http://www.eltima.com/products/serialsplitter/ and if you need the applications on this PC and a remote one to use the same serial data use the combination of both products: SEC and Serial Splitter
To download free trial version of Serial Splitter, please follow the link: http://www.eltima.com/download/serial_splitter.exe