Modem is a kind of wireless communication data transmission module, which can transmit RS232/RS485 data in a wireless way to meet the needs of industrial equipment from short-distance serial communication to wireless remote communication, and can monitor and manage data remotely.
Features of Modem
1, the product is small, simple configuration, a variety of ways to configure.
2. Off-line reconnection, high stability
The software and hardware are equipped with watchdog technology and multiple safeguard equipment, which have the characteristics of automatic reconnection and automatic redialing when the equipment is disconnected. The TCP heartbeat link detection mechanism is adopted to reconnect when the equipment is disconnected and retransmit the data cache. The transmission is stable without packet loss.
3. Full coverage of the networks of the three major operators (all Netcom, supporting 2G/3G/4G)
High-speed wireless transmission is more smooth, compatible with dual SIM cards, so that users have more choices, more simple and convenient.
4. Wide coverage and strong signal
Proprietary impedance matching circuit design and excellent high-quality high-gain antenna make the signal of Modem device stronger, powerful reception ability, and more sensitive signal search response speed. Strong through-wall performance and ultra-wide signal coverage.
6. The compatibility of multiple protocols and interfaces makes the project application more convenient and efficient.
Support RS232, RS485, RS422 multiple interface options, compatible with all serial lower computer
How Modem Works
The most basic usage of Modem is to put a SIM card with 4G function in the Modem, register to the 4G network after the Modem is powered on, and then establish a connection with the data processing center through the 4G network.
This connection involves the wireless network operator, the Internet broadband provider, the network situation of the user's company, and the user's computer configuration, so to establish this connection, all parts need to be configured. In essence, the Modem and the data processing center establish a SOCKET connection. Modem is the client of SOCKET, and the data processing center is the server of SOCKET.
SOCKET connection is divided into TCP protocol and UDP protocol. Modem and center should use the same protocol, which is generally configured by configuration software. After configuring the central IP address and port number for the Modem, the Modem is connected to the user's device through the serial port.
Modem and hydrology, electricity, meteorology, environmental protection and other equipment are connected and placed on the site. After the Modem is powered on, it first registers to the mobile network, then sends a request packet to establish SOCKET to the mobile, and the mobile sends this request to the Internet. After receiving the request, the server software of the center establishes a connection and sends a response message.
The request information sent by the Modem is a data packet on the Internet. There are some reasons that prevent the center from receiving the connection request packet, so the connection cannot be established. The most common is that there are anti-virus software, firewalls and so on on the central computer to shield these data packets. The other is that the central computer accesses the Internet through the router, and data forwarding should be set up on the router. After the SOCKET connection is established, two-way communication is possible.