RealCom Protocol in RS232 to Ethernet

Date：2011-09-01 Author：2Shanghai ZLAN Views：4134

In 232 to Ethernet port there use a protocol called RealCom, which is unfamiliar to users who first use the 232 to Ethernet port. Here is an introduction. 232 is the abbreviation of RS232, which is a kind of serial port, and the COM of Realcom also refers to serial port. The COM1 and COM2 we see on the computer correspond to the 9-pin serial port, because in the early days the communication between the computer is mainly serial port, so the serial port represent communication, COM from the English name "communication". At present, the COM port behind the desktop is RS232 standard serial port.

The Real is actually English "Real" meaning. When the 232 serial port is converted into Ethernet port, on the Ethernet port side, how can you simulate the 232 serial port into Ethernet port, because the protocol of Ethernet port and serial port are different, there needs a Ethernet port protocol (i.e., the TCP/IP protocol) to map Ethernet port to serial port. Thus, it can truly "transform" the Ethernet port to 232 serial ports. The RealCom protocol was born.

RealCom protocol is a network protocol that truly reflects the serial characteristics. After 232 converting to the Ethernet port, the RealCom protocol must implement the reservation of serial port characteristics. The characteristics of 232 serial ports include: baud rate, data bits, stop bits, check bits, and 9th serial port data. RealCom protocol will have corresponding commands and data to transfer these parameters information to the other end of the Ethernet port, so that they can make the program on the network to identify the current parameters, such as the using baud rate of serial port.

The RealCom protocol of 232 to Ethernet port is different from the "Ethernet transparent transport protocol," the data of TCP application layer packet in RealCom protocol is not completely corresponding to 232 serial data, but has a certain frame format. By default ZLAN 232 to Ethernet converter is to use "Ethernet transparent transport protocol", if you need to select for RealCom protocol, you need to set the senior parameters "transformation agreement" of the converter to "RealCom"; Choose the “Ethernet transparent transfer protocol” and set to "No".

The RealCom of 232 to Ethernet generally use cooperatively with the virtual serial port, the underlying drive technology of ZLAN ZLVircom program can add virtual COM port (for example COM5) for Windows, when the 232 to Ethernet port device work in RealCom mode, the virtual serial port driver can dynamic adapt serial protocol parameters through RealCom, the technology is called On-the-fly technology, as assume that ZLVircom program virtually create a COM5, when the user 232 serial port program open COM5, and work on a certain baud rate, data bits, parity, ZLAN virtual serial port driver can automatically detect the serial port parameters, and the parameters are sent to 232 to Ethernet port device in the form of RealCom packets, 232 to Ethernet port device run according to the fixed serial parameters after receiving the commands to realize the serial parameters self-adaptive.

Then, when use the RealCom protocol and when use the “Ethernet transparent transport protocol”? Here are some Suggestions:
1). if don’t use virtual serial port but the Socket communication, the "Ethernet transparent transport protocol" is recommended to be used, because the user does not need serial port parameters self-adaptive, and “Ethernet transparent transmission protocol” has a simple format, easy to implement.
2). ZLAN ZLVircom has double-channel serial port parameter On-the-fly technology. Even if the 232 to Ethernet port device does not adopt the RealCom protocol, ZLVircom can also realize the self-adaptation of serial port parameters. However, when a user needs to across the Internet to use the virtual serial port of ZLVircom, the second channel will be affected, and the RealCom protocol is recommended.