How to analyze COM port activity

Working with serial devices requires to regular monitor and analyze serial port activity. You might need to see data sent and received by RS232/422/485 ports (events from the apps, their status, etc.). This allows you to track down a problem if there is any; it is also extremely handy when you are setting up equipment.

Unfortunately to analyze COM port Windows OS does not offer any special tools. However no need to worry, there is special software that can monitor, check and analyze COM port activity.


  1. Analyze Serial Port Activity with Serial Port Monitor
  2. How to analyze COM port activity?
  3. Compare several monitoring sessions
  4. Reproduce a monitoring session back to the serial port
  5. Advantages of using an RS232 Protocol Analyzer

Analyze Serial Port Activity with
Serial Port Monitor

Serial Port Analyzer is a COM port sniffer developed by Electronic Team, Inc. There is a convenient way to track down problems that may arise when developing an application or a driver, testing and optimizing serial devices, etc.

This convenient tool to analyze serial port activity allows you to:

  1. Connect to a COM port already opened by another application and start monitoring it right away. Our COM Port Analyzer will display in real-time all data received by the serial port, so any possible problem can be tracked down immediately.

  2. Monitor several COM ports simultaneously. Within one session you can analyze remote COM port activity – two, three or several of them – concurrently. Data received and sent is recorded in a single log on a first-in first-out basis; this makes it more convenient for analysis.

  3. View data in a table, line, dump and terminal view mode at the same time. Each of the four monitoring views provide a different way to represent recorded data. You can choose filters for monitoring, so you only see the data for the events you are interested in.

  4. Emulate sending data to a serial device. To do that, use Terminal mode feature of Serial Port Analyzer – it will enable you sending data on behalf of monitored application, various formats (string, binary, octal, decimal, hexadecimal, mixed) are supported. You can thus check how the monitored serial device reacts to specific commands and data.

  5. Fully supports Modbus RTU and Modbus ASCII protocols. Serial Port Analyzer is equipped with new and efficient filters that will help in the reading and analysis of Modbus data. Our software to analyze serial ports opens up the possibility of easily establishing connection with RS485/RS422/RS232 devices, as well as makes it possible to analyze their data.

  6. Playback and session comparison. With COM Port Analyzer comes a unique session playback possibility – the data received from the app can be sent back again to the serial port. This way it becomes easier for you to review the behavior of the port as it receives the same data for more close monitoring results. Also, sessions can be compared with automatic display differences that exist between them.

How to analyze COM port activity using Serial Port Monitor?

First of all, download Serial Port Monitor, install and launch it. Then you need to start a monitoring session, this is how you do it:

  1. In Serial Port Monitor window displayed go to the Main menu, choose Session -> New session. Else, you can click ‘New’ icon on the main toolbar or press ‘Ctrl + N’. This will invoke ‘New monitoring session’ screen.

  2. Select view modes you would like to be displayed during your monitoring session:

    • ★ Table view – recorded IRPs are displayed in the form of table
    • ★ Line view – requests passed through a particular serial line are displayed along with details
    • ★ Dump view – shows data passed through the serial line
    • ★ Terminal view – all received data is displayed in ASCII characters on a text console.

    Serial Port Monitor

    You can utilize ‘Select all’ and ‘Select none’ buttons to simplify things.

  3. Choose, whether you would like to ‘Start monitoring now’ or ‘Start in new window’ for the immediate behavior of a new session.

  4. In ‘Capture options’ specify what events you’d like to capture – Create/Close, Read/Write, Device Control.
    Serial Port Monitor

  5. Click ‘Start monitoring’ to activate the session. This will display a new monitoring window.

  6. To save the session, in the main menu select ‘Session -> Save session/ Save session As’. Alternatively you can click ‘Save’ icon on the main toolbar or press ‘Ctrl + S’.

Name your session to identify it when you go back to it for analysis data.

Compare several monitoring sessions

There are instances where having the ability to monitor the transmissions between multiple serial devices simultaneously can be very advantageous for your IT personnel. A case to consider is a situation where a number of serial monitors have just been installed in an industrial production facility. There is a discrepancy in their readings which needs to be diagnosed, and being able to see all of the devices at the same time can be a big help in troubleshooting the problem. There are many other times where analyzing the data returned by the tool at a later time can be indispensable in solving the issues.

Electronic Team RS232 Port Analyzer allows you to compare several saved sessions to determine the differences between them. Here are the steps to follow when you want to compare your monitoring session with one that was previously saved.

  1. Start or open a monitoring session

  2. Select the “Session” from the main menu and then “Compare Sessions” in the sub-menu.

    Compare Sessions

  3. Select the monitoring files that you want to use.

  4. Now you will have a side-by-side display of the two sessions making it easy to see the differences.

    side-by-side display

Reproduce a monitoring session back to the serial port

There are times where you will want to reproduce previous transmissions between a serial port and a serial application or device. You may be troubleshooting a situation and need to see if your corrective actions were successful. An easy way to accomplish this is to resend the exact same data and review how the components react.

Using Serial Port Analayzer you can easily reproduce the data from a previous monitoring session back to the serial port under investigation. Just follow these steps:

  1. Start or open a monitoring session

  2. Select “Session” from the main menu and the in “Reproduce” in the drop-down menu.

    Select “Session”

  3. Configure the settings as you need. You can control these parameters:

    Configure the settings

    • Use port - allows you to specify the port you will use in the session.

    • Send requests to this port - data written to the serial port by an application can be reproduced with this option.

    • Respond as a device - data written to the port by a serial device can be reproduced with this option.

    • Preserve time intervals - allows you to maintain the time intervals between the data packets.

    • Custom IO timeout - you can choose this option to specify Read/Write timeout parameters. The values are measured in milliseconds.

  4. Now just press “Start”

Advantages of
using an RS232 Protocol Analyzer

Serial Port Analyzer software

Tracking data flow between a computer and its serial ports is not a trivial task. In fact, it is quite difficult if you are not using an RS232 monitoring tool. But by using the tool you can display, monitor, analyze, and log your system’s serial port activity very easily. Developers will find that there are multiple reasons why using a serial port logger can simplify their jobs.
Some of them are:

  1. The ability to monitor a number of serial ports simultaneously. Being able to examine multiple ports at the same time lets you get a clearer overview of the total serial device activity of your system. In addition to the complete representation of your serial connections, you will save time by not having to conduct individual tests on your serial interfaces or devices. Learn more how to test serial port communications in the simplest and most efficient way.

  2. The use of a software COM monitor eliminates the need for extra cables to connect your devices. A hardware solution to serial port monitoring requires expensive cables to connect your devices to the monitor. Besides the cost, there is the office clutter and management headaches associated with the additional cabling for your infrastructure. The financial savings and simplicity of using a software tool like Electronic Team Serial Port Monitor make it an obvious choice over a hardware RS232 monitor.

  3. Time-lag issues and latency are potential problems that can be experienced by developers employing a hardware solution to COM port monitoring. These issues complicate their attempts at monitoring their systems and can be minimized or eliminated by the use of a software-based RS232 protocol analyzer. A well-crafted serial monitor will present the monitored data in a user-friendly interface. The ability to save data to files for later analysis is another important feature of a software monitor. Data transmission and connection events are time-stamped so they can be reviewed easily at a later time in the RS232 activity log.

  4. No programming skills are needed to successfully operate a software COM monitoring solution. Only basic computer skills are required to install the serial port analyzer on your system. After installation, it is a simple matter to monitor and analyze all of the systems’ serial port traffic and can be done by any authorized user.

  5. Use of an RS232 analyzer can be beneficial for many businesses to employ across diverse industrial sectors. All businesses are striving to maximize their resources and gain a competitive edge, and a serial port monitor saves you both time and money. It is an easy choice when you need to keep an eye on your system’s serial traffic.

  6. Your developers and IT staff will save time by using a COM port analyzer. Your business will benefit financially by eliminating expensive cabling and additional monitoring hardware. Various industries such as communications, design services, industrial instrumentation, and semiconductor manufacturing have all used RS232 monitoring software to their advantage. Small companies can more easily compete with their larger rivals by employing this type of software.