Serial to Network Port Tech

With the advancement of technology, the demand for converting serial ports to network ports can now be easily achieved through dedicated serial port to network port conversion modules, which enables traditional serial port devices to conveniently connect to Ethernet. However, this technology is not merely a simple replacement of transmission media, but involves more complex protocol conversions, which include some new issues and misunderstandings that require special attention. The core of converting a serial port to a network port lies in converting the serial port protocol to the TCP/IP protocol. The key technologies involved in this process include the working mode of TCP/IP and serial frame technology, etc. This article will delve deeply into these key technologies to help you better understand and apply the serial port to network port conversion technology.

Serial port to network port or serial port to TCP/IP?

First of all, we need to clarify a concept: A serial port usually refers to a UART (Universal Asynchronous Transceiver), which mainly defines the specifications of the data link layer, including the start bit, data bit, and stop bit, etc. However, depending on different physical layers, serial ports can be further classified into TTL serial ports, RS232 serial ports, RS485 serial ports, etc.

TTL serial port: Mainly used for data communication between MCU chips, logic 1 corresponds to +5V (or +3.3V), and logic 0 corresponds to GND.
– RS232 serial port: It is used for communication between devices. By increasing the signal voltage from 0 to 5V to ±15V (typically ±12V), it enhances the distance and reliability of data transmission.
– RS485 serial port: Suitable for long-distance communication, it can achieve data transmission at the kilometer level. Its main feature is to replace the common-mode signal of RS232 (the voltage between the signal line and GND) with a differential-mode signal, thereby enhancing the ability to resist common-mode interference and enabling longer-distance transmission.

According to ISO’s 7-layer model (physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer), a serial port actually only contains the physical layer and the data link layer. The TCP/IP protocol belongs to the network layer and the transport layer. Therefore, it is not accurate to call it “serial port to TCP/IP”. A more accurate description should be “serial port to Ethernet”. Since most of the protocols running on Ethernet are TCP/IP, “serial port to Ethernet” can also be understood as “serial port to TCP/IP”.

It should be noted that serial port to network port and network port to serial port are actually the same type of two-way mutual conversion technology.

Key Technology One: TCP/IP working mode

The conversion from serial port to Ethernet is not merely a simple conversion between the physical layer and the data link layer. Since the serial port protocol itself does not have a network layer or a transport layer, the conversion of serial port to Ethernet is actually ** treating serial port data as TCP/IP application layer data **, and encapsulating and transmitting it through the TCP/IP protocol. The application layer data of TCP/IP is the truly effective data that needs to be transmitted. Users can receive and send these application layer data through the recv() and send() functions of the socket, thereby achieving the network transmission of serial port data.
However, the working mode of TCP/IP is far more than just recv() and send(). Depending on different application scenarios, TCP/IP can operate in the following modes:
– UDP mode: Based on the connectionless mode, there is no need to establish a connection as long as data can be sent. This mode is relatively close to the serial communication mode, but the UDP protocol cannot guarantee that data will not be lost and is prone to errors.
– TCP mode: It adopts a reliable data transmission mechanism, and data is basically error-free or lost. In TCP communication, it must consist of two ends, one end serving as the TCP client and the other end as the TCP server. The concepts of TCP clients and servers can be compared to making phone calls in communication. The TCP client is the person making the call, while the TCP server is the person receiving the call.

How to choose the TCP/IP working mode?

When choosing the TCP/IP working mode, the following points need to be considered:

TCP vs. UDP: In most cases, especially when it comes to the transmission of large amounts of data, it is recommended to choose TCP mode. Because the UDP mode is prone to data loss and errors, while the TCP mode provides reliable data transmission guarantees.
TCP Client vs. TCP Server: When choosing between a TCP client and a TCP server, the following principles should be followed:
Principle 1: The party initiating data transmission should act as the client. For instance, in a data acquisition system, the acquisition end should act as the client. This is because when a TCP connection is disconnected, the client can proactively establish a connection when it needs to send data. However, TCP servers can only passively accept connections and are unable to actively send data.
Principle 2: In some applications, if a device needs to continuously listen for data requests from other devices, the TCP server mode should be selected. For instance, if a central control system needs to receive data from multiple remote devices, then the system should act as a TCP server, while the remote devices should serve as TCP clients.

The serial port to network port technology greatly expands the application scope and flexibility of traditional serial port devices by connecting them to Ethernet. However, in practical applications, understanding and correctly choosing the TCP/IP working mode is of vital importance. Through the analysis in this article, it is hoped that you can have a deeper understanding of the serial port to network port technology and make more appropriate choices in practical applications.

Whether it is RS232 or RS485, the serial port to network port technology provides new application scenarios and possibilities for them. By rationally configuring and selecting the working mode, you can fully leverage the potential of these devices to achieve efficient and reliable data transmission.