Remote monitoring refers to the technology of remotely monitoring and controlling a target device (server) on a network using remote monitoring software from a single device (client). The operator can monitor the screen display of the controlled device, launch its application, execute commands, and obtain results. Modern remote monitoring technology is a real-time online monitoring method that leverages computer, network, and communication technologies, featuring strong control capabilities, ease of operation, and high reliability. A network fault tester is an embedded handheld device based on the Linux operating system, primarily used for testing network faults in-situ, evaluating performance, and providing expert interpretation. Experts need to spend considerable time and resources to visit the fault site in person; remote monitoring software can help experts access remote test equipment via the internet, understand network operating parameters, provide solutions, and realize a remote expert system. Remote monitoring software will provide portable network fault testers with effective remote operation, monitoring, and remote technical support capabilities. 1. Functions and Structure of Remote Monitoring Software 1.1 Main Software Functions A network fault tester is a portable device, typically connected to the network to be tested. Remote monitoring provides users with the ability to directly observe network status on their personal computers; it also facilitates remote experts in understanding network faults and providing solutions when network failures occur. Therefore, the remote monitoring software primarily implements the operation functions of remote testing instruments, displays the status returned by the devices, and achieves bidirectional data communication through a data exchange channel established between devices. During monitoring, the remote monitoring software acquires control commands issued by the client, and the control server interprets the commands according to the application layer protocol, executes the corresponding actions, and returns the execution results; simultaneously, the server is configured to periodically execute operations and return result data to refresh the interface based on the parameters required by the user interface. 1.2 Software Architecture The software functions are decomposed to two communication endpoints, namely the client and the server, adopting a Client/Server model. This improves design flexibility and facilitates system expansion. The server is integrated into the testing instrument, coordinating with other functional modules of the device, providing the client with a management application interface for executing shared resources; the client provides the interactive interface and result display; the establishment of the data exchange channel is handled by the data communication modules of both parties. This achieves point-to-point direct control and monitoring, meeting real-time requirements. The software architecture is shown in Figure 1. ① The main functional modules of the client are: message input/display module and communication management module. The message input module is responsible for transmitting the button events of the user interface to the communication module. The communication module sends the command information to the controlled end. The success or failure information returned by the controlled end after the operation is executed is handed over to the client message display module for display according to the information format. ② The main functional modules of the server are: communication management module, command interpretation module and function call module. The server is in a listening state. Once a valid connection request is received, a signal path is established. The command information sent by the client is received through the communication management module. After being interpreted by the interpretation module, the corresponding instruction is executed by calling the function and the result is returned to the client. [b]2. Remote monitoring software design[/b] 2.1 Message input/display module implementation The development of the client input/display module adopts Visual C++. Taking advantage of the modularity and versatility, the user interface in remote monitoring is written. The user display interface is consistent with the device interface to facilitate user operation. 2.2 Communication module implementation (1) Socket programming The data channel in the data communication module is established using Socket programming. Socket supports basic operations of TCP/IP protocol network communication; it hides the communication details of the underlying network, making programming simple; it abstracts the communication endpoints, providing a mechanism for sending and receiving data and the ability to open, calculate and close sessions. In this project, the client runs on the Windows operating platform and uses WinSock to program and implement the transmission of commands and data information; while the server runs on the Linux operating platform and communication is directly implemented using Socket programming. (2) Communication establishment Both the server and the client must call the socket() function to generate a Socket socket; then the server calls the bind() function to bind the socket with the local network address and mark the socket on the network; only after the server executes accept() and enters the listening mode and blocking state can it receive the client's connect() request and decide whether to receive data; after the connection is established, the client and the server can transmit data bidirectionally. The main communication code of the server is as follows: listenfd = socket(AF_INET, SOCK_STREAM, 0) bind(listenfd, (SOCKADDR %) &sockaddr_echo, sizeof(struct sockaddr_in)) echofd = accept(listenfd, (SOCKADDR %) (&sockaddrcli), &sizeof(SOCKADDR)); while((read_n = read(echofd, revbuf, BUFLEN)) 0) {. 1 // Instruction interpretation and function call} if((write_n = write(echofd, okbuf, strlen(sendbuff))) 0) {. 1 // Return the result to the client} Wherein, the client and the server establish a unified data communication protocol, and all data and instruction information are uniformly encoded. The encoding format is: command code: data part (the data are separated by #). When transmitting user passwords, a pre-agreed data encryption key is used to prevent information leakage caused by plaintext transmission. 2.3 The application layer of the device application layer includes a Controller call management module, which is responsible for calling the field device test thread, starting the server thread, and transmitting instructions and return results between the server and the test thread. The server receives the client instruction, interprets it through the interpretation module, and then sends it to the Controller. The client then waits for the Controller to return the result parameters to the client. The Controller is the core of the device and is responsible for managing all processes in the device. 2.4 Software Flowchart 2 shows the core software flow. [b]3. Experimental Results[/b] The working process of the remote monitoring system is as follows: The remote client first downloads the client program to the local machine through an IE browser, runs the client program, and the display is shown in Figure 3. The client then enters the server IP address and user password as prompted. After the server accepts the connection and confirms the password is correct, the client displays a function selection interface. Clicking the interface button allows the client to remotely operate the instrument and understand the remote network status. For example, Figure 4 shows the network parameter display results. If the server is not open or the network is down due to a network failure, the user will be prompted "The server is closed or the network is down. Please try again later." Figure 4 User Monitoring Interface [b]4. Conclusion[/b] This study presents a feasible solution for remote monitoring of portable devices based on the Internet. This solution does not require changes to the original device's control system. By adding a data access method, the original device is connected to the remote monitoring platform, enabling monitoring and expert support for remote devices. The remote monitoring software is developed using mature socket programming, achieving device-oriented and function-specific customization. Its modular design facilitates the addition of new functions in the future. The development of remote monitoring based on the Internet has become one of the current research hotspots both domestically and internationally. The Internetization of monitoring networks is a development trend in monitoring technology. With the development of the Internet and monitoring technology, these two networks will inevitably be better integrated, and remote monitoring systems based on the Internet will also develop rapidly. Editor: He Shiping