GPRS DTU working process

　　The most basic usage of GPRS DTU is: put a SIM card with GPRS function in DTU, after DTU is powered on, first register to GPRS network, and then establish connection with data processing center through GPRS network. After the GPRS DTU is powered on, first read the working parameters saved in the internal FLASH (including GPRS dialing parameters, serial baud rate, IP address of data center, etc., which have been configured in advance).consequently Wireless Module I also got a lot of attention and wanted to join the ranks. https://www.hkulike.com/

　　

　　GPRS DTU logs into GSM network, and then dials GPRS PPP. After successful dialing, GPRS DTU will get an internal IP address randomly assigned by Mobile. That is to say, GPRS DTU is in the mobile intranet, and its intranet IP address is usually not fixed and changes with each dial. We can understand that GPRS DTU is a mobile device in the internal LAN, and it communicates with the external Internet public network through the mobile gateway. This is similar to the way that computers in a local area network access external networks through gateways.

　　

　　GPRS DTU actively initiates communication connection with data center, and keeps communication connection always existing. Because GPRS DTU is in the mobile intranet and the IP address is not fixed. Therefore, only GPRS DTU can actively connect to the data center, but not the data center. This requires the 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 is stored as a parameter in the GPRS DTU, so that once the GPRS DTU is powered on and dialed successfully, it can actively connect to the data center.

　　

　　Specifically, GPRS DTU sends TCP or UDP communication requests to the data center through the IP address and port number of the data center. After receiving the response from the center, GPRS DTU thinks that the handshake with the center is successful, and then keeps this communication connection. If the communication connection is interrupted, GPRS DTU will immediately shake hands with the center again.

　　

　　Since the TCP/UDP communication connection has been established, two-way data communication can be carried out.

　　

　　For DTU, as long as the two-way communication with the data center is established, it is relatively simple to complete the conversion between user serial data and GPRS network data packets. Once receiving the user’s serial data, DTU immediately encapsulates the serial data in a TCP/UDP packet and sends it to the data center. Conversely, when DTU receives the TCP/UDP packet from the data center, it takes out the data content and immediately sends it to the user equipment through the serial port.

　　

　　Through the wired data acquisition center, it communicates with many GPRS DTU in two directions at the same time. This is the most commonly used way in GPRS DTU application system at present.