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How to monitor COM port?

How to monitor COM port?

Serial port monitoring is a critical tool for engineers and developers who work with serial communication interfaces. Whether you’re debugging a new piece of hardware or trying to figure out why your application isn’t talking to a serial device, a reliable monitoring technique can be invaluable. In this detailed guide, we’ll explore various tested and effective methods for monitoring serial port activity. I’ll share from my experience the steps to set up and use these tools, ensuring you can capture and analyze the data flowing through your COM ports. Embrace the power of monitoring with ease and precision, fortifying your debugging and development process. For an introduction to serial communication, you can refer to Wikipedia’s page on Serial Communication.


Common Scenarios:

Debugging Complex Systems 💻

  • Serial ports are often used in complex systems with multiple devices communicating simultaneously.
  • Monitoring serial communication helps in understanding the data flow and identifying data corruption or timing issues.
  • Specialized software can simulate serial port activity, log data, and display it in a human-readable format.

Developing Serial Port Applications 🖥

  • When writing software that interacts with serial devices, monitoring is crucial to verify correct data transmission.
  • Developers rely on real-time data capture to test protocols and data packets.
  • Serial port monitors can also be used to emulate serial communications without the actual hardware.

Troubleshooting Communication Errors ⚠

  • Errors in serial communication can arise from incorrect settings or faulty hardware.
  • Using serial port monitors can help identify bottlenecks and conflicts between devices.
  • It’s also essential for analyzing problems like buffer overruns or unexpected interrupts.

Step-by-Step Guide. Com Port Monitoring, Serial Port Sniffer, How To Sniff Serial Port, Serial Port Monitor:

Method 1: Using Hardware Serial Port Monitors 🔧

  • Connect a dedicated serial port monitoring device between the computer and the serial device.
  • Configure the baud rate, parity, and stop bits to match the devices being monitored.
  • View the captured data on the monitor’s screen or direct it to another device for analysis.

Note: These standalone devices are perfect for situations where software-based monitoring solutions are not suitable due to system constraints or security policies.

Conclusion: Hardware monitors are an ideal option for real-time analysis without loading the computer’s CPU.

Method 2: Using Software Serial Port Monitors 💻

  • Install a serial port monitoring application, such as Eltima Serial Port Monitor on your computer.
  • Open the software and configure the session settings to match those of your communication setup.
  • Start the monitoring session and observe the data passing through the COM port.
  • Use filtering and searching features to analyze the relevant data.
  • Save logs and session data for further analysis if required.

Note: Ensure that your serial port is not being used by another application, as this may block the monitoring software.

Conclusion: Software monitors are versatile and provide extensive data logging and analysis tools.

Method 3: Terminal Applications for Serial Communication 🔋

  • Download and install a terminal emulator like Putty or Tera Term.
  • Set up the connection by selecting the COM port and configuring its settings (baud rate, data bits, etc.).
  • Use the terminal’s built-in logging capabilities to track incoming and outgoing data.

Note: Terminal applications are a quick solution but might not offer as detailed insights as specialized monitoring software.

Conclusion: Suitable for simple serial communication tasks and can be quite useful for early-stage development and testing.

Method 4: Wireshark for Serial Port Analysis 🚪

  • Install Wireshark and set up the capture using a virtual COM port setup.
  • Configure the filters to capture only serial port traffic (if needed).
  • Start the capture and observe the packets and their details in a sophisticated interface.

Note: While Wireshark is predominantly known for network analysis, it can be extended for serial communication with additional setup.

Conclusion: An excellent option for capturing and analyzing serial port data with a host of powerful tools at your disposal.

Method 5: Building Custom Monitoring Solutions 🔧

  • Use programming languages like C++ or Python to write your own serial port monitoring scripts.
  • Utilize serial libraries or APIs specific to your operating system for accessing COM port data.
  • Implement logging, displaying, and analyzing functions based on your specific requirements.

Note: Creating custom monitoring solutions requires more time and programming knowledge but offers the utmost flexibility.

Conclusion: Tailor-made solutions can meet specialized needs that off-the-shelf software might not be able to fulfill.


Precautions and Tips:

Sharp Observations 👀

  • Always ensure that the serial port settings in your monitoring tool match those of the devices being monitored.
  • For critical applications, use redundant monitoring methods to cross-verify the data.
  • Often monitor in both directions, as issues can arise in either the sending or receiving end.

Serial Port Fundamentals

Working with serial ports requires attention to detail, as the plethora of parameters such as baud rate, data bits, stop bits, and flow control need to be accurately matched between communicating devices. Despite the advent of more modern interfaces, there are numerous situations where the resilience and simplicity of serial communications make them the first choice.

For educational resources related to serial ports and communications, universities such as MIT offer online materials, while organizations like the PLC Academy provide comprehensive guides and tutorials.

Furthermore, understanding serial protocol specifications is paramount. For instance, Reference for RS-485 offers insights into one of the most widely used serial standards in industrial applications.


Utilizing effective serial port monitoring tools and methods is a game-changer for electronics developers, system integrators, and network administrators. Monitoring provides insights, aids in debugging, and ensures that communications between devices are correctly established and maintained. Whether through hardware, software, or custom methods, being able to capture and analyze serial port data will boost your capability to create robust and reliable systems. Remember to always adhere to the best practices and safety guidelines when working with serial devices to ensure the security and integrity of your systems.


COM port monitoring allows users to observe and analyze the data exchange between serial ports and connected devices, ensuring proper communication flow and troubleshooting issues.

Yes, serial port sniffers can help diagnose hardware problems by capturing and displaying communication data between devices, revealing errors or misconfigurations.

A serial port monitor focuses on the RS-232/422/485 COM ports and USB-to-serial adapters, whereas a network sniffer analyzes Ethernet-based network data traffic.

Yes, advanced COM port monitoring tools can handle simultaneous data capture on multiple ports, aiding in comprehensive system analyses.

Essential features include real-time data capture, filtering and search capabilities, session logging, and the ability to emulate serial communication.

It enables developers to test and debug communication protocols, fine-tune data sending/receiving processes, and ensure interoperability with other devices.

One must have proper authorization to capture data on a COM port, avoid invasion of privacy, and adhere to relevant data protection regulations.

Yes, there are free, open-source tools like com0com, which provide virtual serial port pairing for monitoring purposes.

Efficient serial port monitoring typically has minimal impact on device performance, as it passively captures data without interrupting the communication flow.

Professional serial port monitoring solutions are available from vendors like Eltima Software, which offer advanced features and support.