Serial communication includes three functions: physical layer (physical link transmission, serial port line), data link layer (framing, start bit, data bit, check bit, end bit), and application layer (the packaging of application data is defined by serial port programming).
The relationship between serial port and Ethernet: It is two communication methods, and the implementation principle and application scenarios are different.
Serial port to Ethernet port:
Serial port to Ethernet is not a simple change of transmission medium, but a protocol conversion from serial port to TCP/IP. The key technologies related to it include: TCP/IP working mode problem, serial port framing technology, and 9-bit technology.
The serial port is generally the UART, which actually only defines the specification of the data link layer, that is, the start bit, the data bit, and the stop bit. However, in different physical layers, it is divided into: TTL serial port, RS232 serial port, RS485 serial port, etc.
Since the serial port protocol itself does not have a network layer and a transmission layer, the serial port to the Ethernet port is actually a way to encapsulate and transmit the data of the serial port as the application layer data of TCP/IP. TCP/IP's application layer data is the truly valid data that TCP/IP is intended to transmit. For example, the user receives and sends the application layer data through the recv() and send() functions of the socket. In this way, users can use the recv() and send() functions to send and receive serial port data through serial port to TCP IP user.
The serial server is not the network layer
Serial servers usually do not belong to the network layer, but to the physical layer or data link layer devices.
A serial port is a communication interface used for serial transmission of data, and it is usually used to connect computers with external devices such as printers, modems, etc. A serial port transmits data by sending and receiving a sequential sequence of bits.
The network layer is a layer in a computer network that is responsible for transmitting packets from the source host to the destination host. It handles functions such as network addressing, routing, and packet fragmentation.
Although a serial server is commonly used to connect serial devices to a network, it does not belong to the network layer itself, but rather converts the serial interface into a network interface so that the serial device can communicate over the network. The serial server works at a lower physical layer or data link layer and is responsible for the forwarding and processing of serial data.
What kind of equipment does the serial server belong to?
Serial servers are network devices.
A serial server is a device connected through a network to connect serial devices (such as serial printers, serial terminals, serial sensors, etc.) to a local area network or a wide area network. It encapsulates serial port data into network packets and transmits them over the network to realize remote access and management of serial port devices.
Serial servers usually have network interfaces (such as Ethernet interfaces) and serial interfaces (such as RS-232 and RS-485 interfaces), through which serial port devices can be connected to the network. It can forward serial port data to other devices in the network or remote computers, and forward data received from the network to serial port devices.
Serial servers have a wide range of applications in industrial automation, remote monitoring, Internet of Things and other fields. It provides a convenient and remote way to manage and access serial devices, simplifying the maintenance and management of devices.
Is a serial server a gateway?
Yes, a serial server can usually be used as a gateway.
A gateway is a device that connects two different networks and enables communication between the two networks by forwarding packets. The serial server can act as a gateway to connect serial devices to a local area network or a wide area network, so that serial devices can be remotely accessed and managed through the network.
Usually, the serial port server will provide a network interface and a serial port interface, and realize the remote access of the serial port device by encapsulating the serial port data into network data packets and transmitting them to the remote device through the network. At the same time, it can also parse the data packets received from the network into serial port data and send them to the serial port device through the serial port.
Therefore, the serial server can be regarded as a bridge between the serial port device and the network, acting as a gateway, so that the serial port device can be easily managed and controlled through the network.
The difference between a serial server and a PLC gateway
There are some differences between serial servers and PLC gateways, although they have similar features in some ways.
Function positioning: The serial port server is mainly used to connect the serial port device to the network, so that the serial port device can be remotely managed and accessed through the network. It encapsulates serial data as network packets for transmission. The PLC gateway is more focused on connecting PLCs (programmable logic controllers) of different protocols to upper-layer systems (such as host computers or cloud platforms) to achieve data exchange and communication.
2. Types of devices supported: Serial servers usually support a variety of serial devices, such as serial printers, modems, etc. The PLC gateway is specially used to communicate with the PLC, supporting various PLC devices and communication protocols, such as Modbus, Profibus, EtherNet/IP, etc.
3. Communication protocols: Serial servers usually support common network protocols, such as TCP/IP, HTTP, SSH, etc., in order to remotely manage and access serial devices. PLC gateways need to support specific communication protocols and data formats to exchange data with PLCs, which are usually determined according to the specifications of PLC vendors.
4. Data processing capability: PLC gateways usually have more powerful data processing and conversion capabilities, which can analyze, process and convert the data of PLC equipment to meet the needs of the upper-layer system. The serial port server is usually only responsible for the transmission and forwarding of data, and does not process data.
Although serial servers and PLC gateways overlap in some functions, they differ in design and application scenarios. The choice of which equipment to use should be decided based on your specific needs and type of equipment.
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