The difference between DCE and DTE

DCE (data communication device or data circuit terminal equipment): The device and its connection to the communication network constitute the network Terminal user network interface. It provides a physical connection to the network, forwarding traffic, and provides a clock signal to synchronize data transfer between the DCE device and the DTE device. Both modem and interface cards are examples of DCE devices.
  
DTE (Data terminal equipment): Refers to a device located on the user side of the network interface, which can be used as a source, a beacon, or both. Data terminal equipment is connected to a data network through a data communication device (for example, a modem) and typically uses a clock signal generated by a data communication device. Data terminal equipment includes computers, protocol translators, and multi-channel decomposition devices.

Data Terminal equipment DTE and data line termination devices standard features of the interface between DCE: Mechanical, electrical, functional, process. The mechanical properties specify the actual physical connection details of the DCE and DTE. Electrical characteristics Specify the encoding that DTE and DCE must use, must use the same voltage to describe the same state, and must be using the same width of the signal bits, which determine the data transfer rate and distance that can be reached. Features specify the functions to be completed for each switching circuit. Depending on the functional nature of the interface, the procedure attribute specifies the sequence of events that transmits the data. 

in one respect, DCE is responsible for sending and receiving bits, one bit at a time, on the transmission medium or network. On the other hand, the DCE must interact with the DTE. In general, this requires the exchange of data and control information, which is done through a circuit of the switching circuitry. In order to run this mechanism, the two DCE that exchanged signals on the transmission line or network must understand each other. In addition, each DTE-DCE pair must be designed to work together and interact. In order to make the burden of data processing equipment manufacturers and users easier, the communication interface standards are made. The 

RS-232 interface is an interface between the DTE (data Terminal equipment) and the DCE (data communication device), which includes devices such as computers, terminals, serial printers, and so on. DCE usually only modems (modem) and some switch COM ports are DCE, the standard indicates that the DTE should have a plug (PIN output) DCE has a socket (hole output). This is often overlooked by manufacturers, but it has little impact.
as a user, we must understand the connection between the two.