I. Introduction As a short-range transmission, serial communication is widely used, but it has the disadvantages of small transmission rate and short transmission distance, which greatly limits the development of the entire communication business; and Ethernet has the advantages of fast transmission speed and long distance. It has been widely used and has now become the main communication backbone of the IT industry. Combining the shortcomings of serial communication and the advantages of Ethernet, we designed this networking method to solve the shortcomings of the short transmission distance of serial communication. 2. Scheme design 1. Equipment selection Taiwan 404 Technology ’s NOPORT serial server has 2, 4, 8, or 16 RS-232 serial ports and an Ethernet 10Base2 / T interface. The serial server host can use TCP / IP network to control a large number of distributed serial devices. Such as monitoring terminals, modems, measuring instruments, POS or other industrial equipment, etc. At the same time, the equipment has a variety of models, which can be selected according to needs and flexible networking. The NOport server uses a specially designed Windows NT COMport Redirect driver to enable the Windows NT host on the network to recognize and freely access the RS-232 serial port on the NOPORT server. The stand-alone NOPORT serial server replaces the traditional plug-in multi-serial control scheme. The operation of the original multi-serial card is independent of the Ethernet, which makes the resource planning of the host more efficient, and also provides a simpler multi-serial control scheme. When the system is expanded, as long as the NOPORT serial server is connected to the network, the system does not need to be shut down, nor does it need to remove the case, not to worry about the problem of hardware conflicts. Serial devices can be distributed anywhere through the NOPORT serial server, and connected to the WindowsNT host on the network through the TCP / IP network. At the same time, each WindowsNT host can control up to 256 serial ports to lay a solid foundation for your growing business. Guarantee 921.6Kbps unmatched ultra-high speed transmission performance and convenient maintenance program. As for the NOPORT serial server, no matter adding or replacing the NOPORT serial server, there is no need to stop the operation of the host, nor does it need to disassemble the host casing. 2. Networking solution The networking scheme is as follows. Networking plan description: The monitoring hosts are distributed anywhere in the network, not limited to the equipment room. Many monitoring hosts are connected to the multi-service switch (which can be used to transmit data, voice, and images) through the network hub, and transmit the data through the multi-service switch To the network transmission channel, these network transmission channels include microwave, Ethernet, and optical fiber, which can be selected according to specific circumstances. Then, the data on the transmission channel is deciphered through the multi-service switch at the opposite end and sent to the peer network hub. According to the host's needs, a certain serial port server and a certain serial port are selected to monitor and control the device operation data. Device configuration: On the same network, the serial port communication port number is uniformly assigned by the monitoring host under the driver's role. The maximum serial number can reach 255. The IP address of the monitoring host and the server's IP address are set on the same network segment , Set the subnet mask and gateway to the same. 3. Communication speed guarantee of serial port Limited to factors such as communication distance, anti-jamming capability and software data flow control, when the original main control unit and each interval device adopt RS-232 / 485 communication, the communication baud rate is generally 9600bps, sometimes 19200bps or 38400bps to ensure stable When data is transmitted, the transmission distance is very close; after the combination of serial communication and Ethernet technology, the communication rate of the Ethernet part can reach 10M / 100M. Because the communication distance of the serial part is greatly shortened, the use of high-speed communication has been technically guaranteed, and From the actual test and operation results, it is feasible to increase the communication baud rate to 38400bps. 3. Network operation 1. Equipment operation environment guarantee The reliability of the equipment in harsh environments is the most concern of users. How to make Ethernet products work like industrial computers, interval protection, measurement and control units and PLCs for long-term reliable operation under harsh field conditions is the main problem to be solved. It can work reliably under a wide temperature range, generally -5 ℃ ~ + 55 ℃, special requirements are -40 ℃ ~ + 80 ℃; it has a method suitable for industrial installation, such as DIN standard rail installation, strong anti-vibration and anti-corrosion , Moisture-proof, explosion-proof and other measures; long-term, reliable, and uninterrupted use, preferably 10 to 20 years; using highly reliable mechanical and electrical structures to prevent environmental problems that shorten the life of the equipment, using redundant measures to increase the system ’s Reliability, such as redundant power input. 2. Network operation process The monitoring host packages the data and sends it to the Internet. According to the header data of the TCP / IP data packet, it looks for the serial port number of the NPORT serial port server on the Ethernet. Unpack and restore to the monitored device, let the monitored device work according to the instructions sent by the monitoring host, and collect data. After receiving the data collection instruction, the monitoring equipment starts to work, and transmits its operation data to the NOPORT serial server through the serial communication port. The NOPORT serial server encapsulates the received equipment operation data, converts the format, and transfers the received data. The data stream converted into TCP / IP protocol format is searched on the Ethernet according to the IP address of the monitoring host. Once the requested monitoring host is found, the packaged IP data stream is sent to the monitoring host for processing to complete a monitoring activity. 4. Conclusion Using this networking method and using the TCP / IP transmission protocol, there is a reliable data transmission service between the controlled device and the monitoring host, which ensures that the communication packets between the controlled device and the monitoring host will not be lost, nor It will be repeated. The monitoring host can be placed in any place where Ethernet exists, eliminating the limitation that the monitoring host can only be stored in the equipment room, making the monitoring system structure simple, centralized monitoring easier, and the transmission distance more remote. The automatic control process of the Huaihe Flood Control Communication System has played an important role. 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