232 The RealCom protocol in the Network Interface

First of all, I do not know much about the hardware or devices, for the underlying protocol communication, it is just a glimpse of what we learned due to problems today. www.2cto.com we transmit SNMP packets to the device through the TCP protocol to retrieve data, because the device uses a serial port, communication between us uses a protocol converter to connect the serial port to the network port. However, one problem is that I can send data to the device, but I cannot receive the data and capture the packet, each time the returned content contains 6 more bytes, no one knows why such a thing exists. I tried to open a port for the device to send it. I found that I had received 6 bytes of data. The last careful colleague found that there was a RealCom configuration switch on the converter configuration page, after this feature is disabled, the six bytes will not appear. You can check the Internet to know that there is such a thing as the RealCom protocol.
The following is from the network and is for reference only: a protocol called RealCom is used in the 1.232-to-net port and the RealCom name. Users who use the 232-to-net port for the first time are unfamiliar with this Protocol, here is an introduction. 232 is the abbreviation of RS232, which is a type of serial port. Here, the COM of realcom also refers to the serial port. We can see on the computer that COM1 and COM2 correspond to this 9-pin serial port, because the communication between early computers was dominated by serial ports, so the serial port represents communication, COM is from the English name "communication ". At present, the comport behind the desktop is the RS232 standard serial port. Www.2cto.com
Whether the serial port to the network port corresponds to the network port of Real since COM corresponds to 232 in RealCom. Not exactly. The network port is RJ45 or Ethernet port. Real actually means "Real" in English. After the 232 serial port is switched to the network port, you can see at the end of the network port how to simulate the network port as a 232 serial port, because the network port and the serial port are different in their own protocol, A network port (the Protocol over TCP/IP) is required to map the network port to a serial port. In this way, the network port can be converted to a serial port of 232. So the RealCom protocol was born.
2.232 the RealCom protocol in the network interface is a network protocol that truly reflects the characteristics of the serial port. After 232 is switched to the network port, the RealCom protocol must retain the features of the serial port. The features of the 232 serial port include the baud rate, data bit, stop bit, check bit, and 9th-bit serial port data. In the RealCom protocol, corresponding commands and data bits are used to transmit the parameter information of the serial port to the other end of the network port, so that the program on the network can identify parameters such as the baud rate used by the current serial port. The RealCom protocol in the 232 to-net port is different from the "Ethernet transparent transmission protocol". The data of the TCP Application Layer of the RealCom protocol does not fully correspond to the data of the 232 serial port, but has a certain frame format. By default, the Zhuo LAN 232 network port Converter uses the "Ethernet transparent transmission protocol". To select the RealCom protocol, you need to set the advanced parameters in the parameters of the converter: set "conversion protocol" to "RealCom" and "Ethernet transparent transmission protocol" to "NONE ".
232 The RealCom in the network interface is generally used in combination with the virtual serial port. The underlying Driver technology of Zhuo LAN ZLVircom can add a virtual comport (such as COM5) for windows ), when the 232-to-net port device works in the RealCom mode, the virtual serial port driver can dynamically adapt the serial port parameters through the RealCom protocol. This technology is called the On-the-fly technology, assume that the ZLVirCom program virtualizes A COM5. When the user starts the 232 serial port program and runs at a certain baud rate, data bit, and check bit, the Zhuo LAN virtual serial port driver can automatically detect this serial port parameter, in addition, this parameter is sent to the 232-to-the-net port device in the form of RealCom data packets. After receiving the command, the 232-to-the-net port device runs according to the specified serial port parameters, realizing adaptive serial port parameters. Www.2cto.com
When the RealCom protocol is used and when the "Ethernet transparent transmission protocol" is used ". (1) If Socket communication is not needed, we recommend that you use the "Ethernet transparent transmission protocol" because at this time, you do not need to adapt the parameters of the serial port, the "Ethernet transparent transmission protocol" has a simple format for easy implementation. (2) Zhuo LAN ZLVircom has a dual-channel serial port parameter On-the-fly technology. Even if the 232-to-net port device does not adopt the RealCom protocol, ZLVircom can also realize adaptive serial port parameter. However, when you need to use the virtual serial port of ZLVircom across the Internet, the second channel will be affected. We recommend that you use the RealCom protocol. The Zhuo LAN ZLVircom mentioned above is also a conversion device. When we are not using a brand, the extra bytes are actually a kind of information, which includes the features of restructured communication. If you do not need a feature description, you can use the Ethernet transparent transmission protocol. If you have special applications, you should select the RealCom protocol. If you use the RealCom protocol, you should also perform a conversion yourself, remove the additional feature description, otherwise it will not be recognized in SNMP communication because it does not belong to the standard SNMP package.