The Ultimate com0com
Distribution Hub

Unlimited Port Pairs

Create an unlimited number of virtual COM port pairs. Each pair acts as a transparent bridge, allowing data sent to one port to be instantly received by the other, mimicking a physical null-modem cable.

Kernel-Mode Stability

Unlike user-mode wrappers, com0com runs as a kernel-mode virtual serial port driver. This ensures maximum data integrity, low latency, and full compatibility with legacy Windows and DOS applications.

Advanced Emulation

Supports Baud Rate Emulation, 7/8-bit data, and parity control. You can also simulate line noise or buffer overruns to test the robustness of your serial communication software under extreme conditions.

Network Extension

Compatible with com2tcp and hub4com. Easily redirect local COM port data to remote TCP/IP servers or share a single serial device among multiple applications simultaneously.

Flexible Naming

Fully customizable port naming. Change default names like CNCA0 to standard COM3, COM4, or COM10 to ensure compatibility with third-party software that only recognizes standard port identifiers.

GPL Open Source

Freely available under the GNU General Public License. No hidden fees, no trial periods, and no limitations. Ideal for developers, students, and engineers looking for a professional-grade tool.

Versatile Solutions for Engineers & Developers

From amateur radio to industrial automation, com0com provides the virtual infrastructure needed to bridge the gap between software and hardware emulation.

Q: Does com0com work on Windows 11 and Windows 10 (64-bit)?

Yes. While the original builds often struggle with driver signature enforcement, our 2026 distribution includes verified digital signatures. This allows com0com to load correctly on Windows 11 and 10 x64 without needing to enable “Test Mode” or disable “Secure Boot.”

Q: Why are the ports named CNCA0 and CNCB0 by default?

These are the internal names used by the driver. However, you can easily change them to standard names like COM3 or COM10 using the SetupG GUI tool. Simply check the “Virtual Port ID” option or use the change command in the setup prompt.

Q: Is com0com really free to use for commercial projects?

Absolutely. com0com is licensed under the GPL (GNU General Public License). This means it is free for both personal and commercial use. You are also welcome to view, modify, and distribute the source code.

Q: How do I fix the “Digital Signature” error (Code 52)?

This error occurs when Windows blocks an unsigned driver. To fix this, you should uninstall the old version and download our Signed Build. If you must use an unsigned version, you will need to run bcdedit -set TESTSIGNING ON in an Admin Command Prompt and reboot.

Q: Can I use com0com to share one GPS device with multiple apps?

While com0com creates pairs, you can combine it with hub4com (included in our advanced package) to split one physical serial signal into multiple virtual ports, allowing several applications to read the same data stream simultaneously.

Supported Platforms

• Windows 11 (Home, Pro, Enterprise)
• Windows 10, 8.1, 7 (x86/x64)
• Windows Server 2016 – 2022
• ReactOS Compatibility

Protocol Support

• RFC 2217 (with hub4com)
• Full Modem Signal Support (CTS, RTS, DSR, DTR, DCD, RI)
• Break Signal Handling
• Custom Pin Wiring Emulation

Advanced Features

• Noise Simulation (Data Corruption Test)
• Buffer Overrun Emulation
• Exclusive Mode (Hidden Ports)
• Multi-Port Hubbing (N-way Splitter)

Windows cannot verify the digital signature for this device. This usually happens with the original 3.0.0.0 unsigned build on 64-bit systems.

Your application hangs when sending data because the receiving buffer is full and overrun is disabled by default.

Third-party software does not see CNCA0 as a valid COM port. Many legacy apps only scan for “COMx” names.

hub4com

The Communication HUB allows you to handle data and signals from a single serial device by a number of different applications. It acts as a sophisticated serial port splitter and multiplexer.

• Share one GPS device with multiple apps
• RFC 2217 compliant terminal server
• Redirect serial data to multiple TCP/IP clients

com2tcp

A specialized COM port to TCP redirector. Connect legacy serial software to modern network infrastructure by encapsulating serial data into TCP/IP packets.

• Remote serial port access over LAN/Internet
• Integrate legacy devices into IoT cloud systems
• Supports client and server listening modes

SEO Pro Tip: If you’re building a Serial-over-Ethernet solution, com0com provides the virtual interface, while hub4com handles the network logic. Together, they form a robust, open-source alternative to expensive commercial serial redirectors.

Seamless Integration for Developers

com0com ports behave exactly like physical hardware, making them compatible with every major programming language and serial library.

# Connecting to a com0com pair
import serial

# Open the first port of the pair
ser = serial.Serial('COM10', 9600, timeout=1)

# Send data to CNCB0/COM11
ser.write(b'Hello from com0com')

print("Data bridged via kernel driver.")
ser.close()

*Requires com0com virtual ports to be renamed to standard COM identifiers.

“Finally, a version that works on Windows 11 without that annoying ‘Test Mode’ watermark. I use it to bridge my SDR software and CAT control for amateur radio. It’s flawless and zero latency.”

“We needed a reliable way to simulate Modbus RTU communication between our SCADA and a virtual PLC. com0com is the only open-source tool that handled the kernel-level timing accurately.”

“The signed driver on this site saved me hours of frustration. As a Python developer, being able to quickly create virtual pairs for unit testing serial protocols is a game changer. Highly recommend!”

Built on Trust and Transparency

As a critical kernel-mode component, we understand that security is your top priority. Our distribution of com0com is focused on integrity, compliance, and modern safety standards.

com0com.com

The premier resource for the Null-modem emulator (com0com) driver. Providing signed, secure, and reliable virtual serial solutions for modern Windows environments.

Resources

• Download Now
• Setup Guide
• Troubleshooting

Project

• SourceForge Page
• GitHub Mirror
• Privacy Policy