List of the best RS232 Sniffers

What is an RS232 sniffer?

Serial Port Sniffer is a specialized system utility that captures serial data packets transferred by another program to a serial app or device over an RS232 interface.

With an efficient sniffer tool, you can monitor the activity of any COM port in your system. Also, it will help you test serial applications or device drivers you’re developing. If the monitored program is created by you, your COM port sniffer can serve as an RS232 debugger allowing you to track down errors which may occur during serial data exchange.

RS232 sniffer software. The advantages of serial port monitoring apps

Serial Port Sniffer by Eltima

Can you imagine an ideal Serial Port Sniffer software? Probably you would expect it to be a simple yet functional solution able to easily read, record and display data transmitted through any real or virtual serial port available in your Windows system. Luckily, all these and many other advanced capabilities are offered by a dedicated Serial Port Sniffer utility developed by Eltima Software.

Serial Port Sniffer is a convenient tool that sniff and analyze data transfer COM port activity and intercept traffic.
Serial Port Monitor logo

Serial Port Monitor

Log and analyze serial port activity
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Serial Port Monitor

Eltima’s solution is one of the most popular professional apps for data sniffing and logging. It provides convenient filtering and search options, built-in terminal, and four different data visualizers which can display the captured serial data in different formats. You can select table, line, dump, or terminal mode or enable all of the views at a time. Also, can easily use RS485 sniffer for decode industrial protocols such as Modbus RTU, Modbus ASCII, Modbus TCP/IP.

With this Serial Port Sniffer, you’ll be able to access and start logging data from COM ports which have already been used by other utilities. To achieve this, simply:

  1. Download and install Serial Port Sniffer on your PC.

  2. Launch the app and start a new monitoring session by selecting “Session > New session” in the main menu.

  3. After that, In the invoked window, choose a serial port to monitor and enable the required options. You’ll be able to select the desired viewing mode, start a new session in a new window, and specify the events you are interested in: creating, closing, writing, reading, device control.

  4. Then click “Start monitoring” and that’s it! Now you can sniff your system’s serial ports in real time.

2. HDD Serial Port Monitor

HDD Serial Port Monitor is another friendly COM port sniffer for Windows, which allows monitoring and recording data from RS-232, RS-422, and RS-485 interfaces. This handy solution will help you easily analyze serial port activity and detect any issues with serial data communications.

Serial Port Monitor by HDD software

Serial Port Monitor freeware gives you the way to sniff several COM ports simultaneously, so you can see how your apps interact with several serial devices within one session.

This app is especially useful for those who develop serial software, device drivers or serial hardware. It is a convenient tool for testing, debugging, and optimizing RS232 products.

One of the key advantages of this solution is that you can use this software sniffer of RS232 ports for free, but with limitation.

Serial Monitor is a reliable solution which works with high data transfer rates and makes it possible to easily change the way the raw data is displayed. Even if the session is completed you can still save the monitored data for its further analysis. This RS232 serial communication software is friendly and flexible and definitely deserves your attention if you’re a serial app developer or tester.

3. Serial Port Sniffer by AGG Software

Serial Port Sniffer by AGG Software can monitor all traffic sent and received by a particular serial port. What’s especially convenient is that the data sent can be highlighted in the software window.

Serial Port Sniffer by AGG Software

This serial port sniffer will also display the transferred data in any format (hexadecimal, decimal, or any other). This way you can identify the repeated sequence of data blocks without closing the monitoring app.

Compared to most other com port sniffers, Serial Port Monitor by AGG Software has several major advantages:

  • The software is able to work across a wide range of Windows platforms, starting with Windows 2000 and ending with Windows 10 (x64);

  • With this program, you can monitor the transmission of data via all serial ports available in your system. You can sniff from 1 to 255 ports;

  • Serial Port Monitor allows you to capture the traffic transmitted during a dial-up connection, and more.

RS232 Sniffer Hardware Solution. Hardware serial port sniffer tools

1. Avisaro RS232 "Sniffer" Interface

Logging of serial port data is no longer a problem for those who use RS232 bidirectional data sniffing interface provided by Avisaro.


The compact hardware unit is designed to record data communicated between two devices over the RS232 protocol. Together with the Avisaro Data Logger app, this sniffer box is used to capture data transmitted in both the Rx and Tx directions and store it in a table format. That means you can use Excel or any text editor to read your serial data.

RS232 "Sniffer" Interface is widely applied for RS232 communication debugging and re-engineering of data protocols.

2. EZ-Tap RS232 Pro RS232 sniffer

RS232 hardware sniffer produced by Stratus Engineering will help you resolve the latency and time-tagging issues commonly faced by users of traditional dual COM port sniffing tools.

EZ-Tap RS232 Pro RS232 sniffer

The clear benefits you get with EZ-Tap RS232 Pro hardware:

  • No need to rely on bulky and expansive RS232 sniffer cables;
  • You can track down the activity of multiple serial interfaces at a time and redirect the monitoring data to a file;
  • The app provides simple access to serial ports and logging of all the data sent and received;

  • EZ-Tap RS232 Pro fully supports Windows 2000/XP/Vista/7/10 (x32 and x64);

  • Together with the hardware Com Port Sniffer, you receive the device drivers, Mini-B USB cable and a dedicated EZ-View monitoring software.

This RS232 packet analyzer can monitor full and half duplex serial communications and stream data to a dedicated RS232CPM COM monitor application.As well as an active rs232 sniffer cable that monitors the DTE/DCE and RTS/CTS lines in addition and Tx/Rx lines. EZ-Tap RS232 Pro is equipped with a male DB9 connector on one end and a female DB9 connector on the other end. Thanks to this, it can be inserted between two COM-based devices that need to be sniffed.

To use this solution, you just need to connect it to a USB port of your PC with the help of a USB A to mini B cable, install its drivers as well as the supplied RS232CPM app and start sniffing.

A nice thing about the RS232 COM Tap is that it can also be used with any RS232 terminal app supporting virtual COM ports, for instance, Windows HyperTerminal.

3. Serial Tap by Tibbo

The Hardware Serial Tap is a simple yet efficient sniffer tailored for monitoring of RS232, RS485, and TTL-level UART communications. This sniffer board is natively supported via the Serial Tap plugin.

Serial Tap

Here’s how the solution works:

  • You connect your Serial Tap hardware over a USB cable and select it in the Serial Tap plugin.

  • Next, you specify the baud rate at which the serial communication you are going to sniff works.

  • Then, you click Capture and get the communication data displayed. In addition to serial data, you’ll see all control line changes and status line changes. This is it.

Modbus Sniffer

Modbus is a master/slave serial communication protocol popular in the industrial environment mainly because it’s openly published and royalty-free. Originally It was used to connect various industrial electronic devices over RS-485 protocol, though many other versions are available now for RS-232, RS-422, and TCP/IP (Modbus TCP) protocols.

Modbus protocol has a broad scope of application, particularly Modbus ASCII and Modbus RTU versions. The second is used the most among all Modbus protocols. So, if you are in the process of developing software to communicate with some electronic devices through the Modbus RTU, you’re definitely going to need a high- grade Modbus RTU sniffer. It’s a specialized RS485 Protocol Analyzer that will help you to analyze data sent through the protocol. The same applies to the Modbus ASCII version, with the only difference that you’ll need another version of a port scanner software.

Modbus Sniffer by Eltima Software allows you to not only monitor all the relevant data sent through Modbus ASCII and Modbus RTU protocols but also log it for future analysis. It has a user-friendly interface and displays data in different view modes. On top of that, this particular protocol analyzer provides an opportunity to filter collected data for more accurate analysis.

Modbus sniffer software

With this professional-grade Modbus sniffer software
you’ll be able to:

  • Establish a connection with any serial port and instantly get a full real-time view of all the information transferred through it, so you can straightaway fix all the emerging problems. Even if some other application is already using that port at the very same time, it won't stop Modbus Sniffer to effectively carry out its task.

  • Simultaneously monitor multiple serial ports and conveniently log all the gathered information into a single file by the first-in-first-out principle.

  • Choose the modes to display captured data: table, line, dump or terminal. Use them in any combination and apply filters for a more accurate and comprehensive analysis.

  • Check the serial device’s response to specific commands with an emulated transmission of data.

  • Use the terminal mode to emulate data transmission from a monitored serial port to a device that is connected to it. This feature might be particularly useful during the Modbus communication test, given that it provides means to monitor any given device responds to certain commands or data.


There’s plenty of efficient software and hardware serial port sniffer tools able to meet your most specific needs. However, considering that a software solution like Eltima’s Serial Port Sniffer is much easier to install and configure than any hardware serial monitor, it seems to be the most optimal method to monitor RS232 communications. In addition, pricing is usually a bit higher for a piece of hardware (supplied with a controlling app, cables, and connectors) than for a standalone sniffer program.

Serial Port Monitor

Requirements: Windows (32-bit and 64-bit): XP/2003/2008/Vista/7/8/10, Windows Server 2012, Windows Server 2012/2016/2019 , 8.15MB size
Version 8.0.388 (7 Jul, 2020) Release notes
Category: Serial Port Software