DTU stands for data transmission unit, it uses 5G or 4G wireless or wired networks to package local serial port data into IP data through DTU or convert IP data into serial port data for remote transmission.

After DTU is powered on, it will connect to nearest base station automatically. For example, 5G or 4G DTU will log into 5G or 4G network automatically once it is powered on, then make a call, DTU will obtain a dynamic IP address assigned by the operator after successful calling.In other words, DTU is in the mobile intranet, and its intranet IP address is not fixed but changes with each dialing. We can consider that DTU is a device in the mobile internal LAN at this time, communicate external Internet public network with mobile gateway, this is similar to computers in a LAN access external networks through a gateway.

DTU actively initiates communication connection with data center and keeps the communication connection always online. Because DTU is in mobile intranet and the IP address is not fixed, so DTU can only actively connect to data center, but data center cannot actively connect to DTU. This requires data center to have a fixed public IP address or a fixed domain name, the public IP address or fixed domain name of the data center will be stored in DTU as a parameter, so that once DTU is powered on and dials up successfully it can actively connect to the data center.

Specifically, DTU initiates TCP or UDP communication request to data center with IP address of data center (first resolve the central IP address with the central domain name if use the central domain name) or parameters such as port number etc., DTU will be considered handshake with center is successful after getting response from the center, then keeps the communication connection online, DTU will handshake with center again if communication is disconnected. Since TCP/UDP communication connection has been established, two-way data communication can be carried out.

For DTU, it is relatively simple to complete the conversion of user serial port data between network data packet as long as two-way communication with data center is established. Once receive user’s serial port data, DTU will encapsulates serial port data into a TCP/UDP packet and send it to the data center immediately. On the contrary, when DTU receive TCP/UDP packet from data center, it will take out the data content and send it to the user device with serial port immediately.

Through the wired data collection center, two-way communication is performed with many DTUs at the same time is the most popular used methods in current DTU application systems.