I want to connect my program which using serial port to control through internet my plc.

Yes. The Netport connects serial devices to ethernet networks, allowing you to send serial data across the network, using a technique known as serial tunnelling.

The netport can be used in two modes.

• Single Netport mode: the Netport is connected to the PLC. A virtual serial port is installed onto a PC. Software on the PC can then talk to the remote serial device over the network. Whilst theoretically the PLC and the PC can be any distance apart, in practice the distance may introduce some latency into the system. That may be a problem if timings in the communication between the software and PLC are important
• Two Netport mode: the second mode uses two Netports. One Netport is connected to the PLC and it then talks to the second Netport over the network. The second Netport can then be plugged into another device or PC using a serial cable.