How can you monitor or sniff Serial (COM Port) data? This is a recurring question among software and embedded solution developers.
COM Sniffer is one of the most advanced Windows software tools to monitor, log, and sniff all serial port traffic, even when the port is already open by another application. This way you can see all the data passing through the COM port, without hardware intervention.
It works with RS-232/RS-422/RS-485 connections and with USB-to-Serial adapters. COM Sniffer captures data without limitations, allows saving them to file, and exporting them in PCAP (.pcap) format, so you can analyze them with Wireshark or any other protocol analyzer.
COM Sniffer is now integrated into SerialTool, one of the most powerful free and cross-platform software tools for serial communication, available for Windows, macOS, and Linux. Once SerialTool is installed, COM Sniffer is ready to use and lets you immediately start sniffing the serial (COM) port.
COM Sniffer lets you keep LOG and PAYLOAD separated — that is, incoming data (IRP_MJ_READ) and outgoing data (IRP_MJ_WRITE) on the serial port — so you can instantly view all traffic clearly and intuitively.
In addition, COM Sniffer allows you to monitor multiple serial ports at the same time, without practical limits. Log files are automatically organized into separate archives per port (and per session), simplifying analysis and traceability.
COM Sniffer supports any serial port, including virtual serial ports created in Windows with tools like SerialTool.
COM Sniffer allows you to filter low-level commands sent to the serial port, so you can focus only on IOCTL_SERIAL or IRPs of interest, without having to view all traffic. This way you get a quick and readable overview of what’s happening, focusing on what matters without analyzing every single packet.
If you are developers or hobbyists creating applications in Windows, it is essential to verify that the serial port is correctly configured and meets the requirements of your hardware. In this, COM Sniffer is an indispensable tool for anyone developing software that uses the COM port.
With COM Sniffer you can understand exactly how your code behaves in using the serial port without resorting to equipment such as an oscilloscope. You can monitor port opening, baud rate setting, RTS/DTR signal status, and obtain millisecond timing on your application’s behavior, avoiding bugs that often take days to identify.
It is also ideal when working with proprietary hardware or in embedded environments: it helps you understand if there are communication issues and how the operating system forwards your data on the serial port. Moreover, you can observe how third-party software performs the same operations, carry out targeted reverse engineering, and significantly improve the quality and professionalism of your application.
