The serial port networking server is also called serial port server. The two keywords are serial port and network. The network is divided into two types: internal network and external network. The internal network generally refers to Ethernet, and the external network refers to the Internet. It is an effective means for communication on a global scale. Before the network is popular, data exchange is usually carried out between the device and the computer through simple RS232; if long distance transmission is required, RS485 can also be used (normal RS485 can transmit 1200 meters, industrial grade can transmit 5000 meters).