What is the principle of the 4G DTU
The communication between 4G DTU and the server is conducted by 4G DTUterminal (client). The server did not respond to the 4G DTU based on the feedback returned, or the communication is accepted.4G DTU and server have formed an application system based on 4G communication and Internet technology network communication. Compared with 4G DTU terminal equipment, network server terminal equipment is equipped with more complex mobile applications that can accept all communication requests from 4G DTU terminal equipment and view the communication status of the link anytime and anywhere, so as to realize the application of real-time data collection and database services.
4G DTU requires to know the IP address and port number of the server before it can initiate a communication request. Once the communication is established, there is no difference between the server and the 4G DTU.
The IP address of the server can be a public network IP (fixed IP) or a dynamic domain name obtained through the domain name resolution server.
The server port number generally matches the special mobile application running in the server. For example, the FTP service project uses the port number TCP 21, and the dynamic Web server (H http) uses the port number TCP 80. In other words, server-side mobile applications are suitable for pushing and receiving data based on special server ports.
Generally, the IP address obtained by 4G DTU terminals is the Intranet IP address randomly assigned by the network operator, and the Internet network can be accessed through the gateway of the mobile operator. In particular, the NAT (Network Address Conversion) port mapping service has a short time limit, so if you need to maintain bidirectional communication, a scheduled 4G DTU heartbeat packet must be set up to maintain the NAT port mapping.
● Connection mode: support 4G, 2G, 3G, network
● Transmission mode: transparent data transmission, configuration software protocol
● Transmission protocol: support TCP, UDP, MQTT, AT instruction control
● Data center: support dynamic domain name and fixed IP address access, multi-backup data center
● Efficient: cache function to ensure that data is not lost
● Flexible: support real-time online, support SMS, telephone, serial port data and other remote wake-up mode
● Managed: the 4G DTU can be remotely configured and queried through SMS
● Easy maintenance: Support for local firmware upgrades
1. Internal integration of the TCP / IP protocol stack
The 4G DTU packages both the PPP dial-up protocol and the TCP / IP protocol stack, and has an embedded operating system. Hardware can be viewed as a combination of embedded PC and wireless 4G MODEM; it has 4G dial-up Internet access and TCP / IP data communication function.
2. Provide the two-way conversion function of serial port data
4G DTU provides serial communication interface, including RS232, RS485, RS422 and so on are commonly used serial communication mode, while the 4G DTU design is mostly the serial port data into "transparent transmission" mode, that is to say, 4G DTU can convert the original data on the serial port into TCP / IP data packets for transmission, without changing the original data communication content. Therefore, the 4G DTU can be connected to various user devices through serial communication without modifying the user devices. It greatly facilitates the transmission process and does not require complex protocol conversion.
3. Support automatic heartbeat, permanent online
One of the advantages of 4G DTU devices is the support for permanently online 4G DTU terminal devices.Therefore, the typical 4G DTU is intended to support permanent online functionality. This requires that the 4G DTU include automatic dialing and the heartbeat packet to remain permanently online (when there is no data communication for a long time, the mobile gateway will disconnect the 4G DTU from the center. The heartbeat packet is disconnected by the 4G DTU from the data center before keeping the connection from being disconnected.) Equipped with watchdog technology, double protection equipment, automatic reconnection when the equipment disconnect, automatic redial and other functions.
4. Support for parameter configuration and permanent storage
4G DTU is widely used as a communication device. In different applications, the IP address and port number of the data center and the baud rate of the serial port are different. Therefore, a 4G DTU should support parameter configuration and store the configuration parameters in an internal permanent storage device (typically a FLASH or EEPROM, etc.) . Once power on, it will automatically work according to the set parameters.
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