VSerial creates virtual COM port pairs (e.g. COM10 <-> COM11) on Windows. Data written to one port is immediately available to read from the other, with full hardware flow control signal mapping (RTS/CTS, DTR/DSR/DCD).
It includes:
- GUI (
vserial-gui.exe): A desktop application for viewing and managing port pairs. - CLI (
vserial.exe): A command-line tool for scripting and automated environments. - UMDF 2.0 Driver: A user-mode driver that runs in user space rather than the Windows kernel.
For years, com0com was the standard utility for virtual serial ports on Windows. However, running it on modern Windows 10 and 11 presents practical issues:
- Kernel Driver Stability: com0com runs as a legacy kernel-mode driver (KMDF 0.9 / Ring 0). Unexpected concurrency or buffer states can cause a system crash (BSOD).
- Driver Signature Enforcement: Its driver signatures frequently conflict with UEFI Secure Boot and modern Windows driver policies, causing installation failures.
- Small Buffer Size: The default 1 KB buffer easily overflows during continuous high-baud-rate or burst transmissions.
- Maintenance: Upstream development has been inactive for an extended period.
VSerial addresses these issues by using Microsoft's User-Mode Driver Framework 2.0 (UMDF 2.0). The driver executes inside the user-mode driver host process (WUDFHost.exe), isolating any driver faults from the OS kernel. The in-memory buffer is expanded to 64 KB per direction, and ports can be added or removed dynamically without restarting the system.
- In-Memory Null-Modem Emulation: Direct memory transfer between paired ports with standard serial event support (
WaitCommEvent). - Hardware Flow Control: Interlocked signal lines (RTS <-> CTS, DTR <-> DSR/DCD).
- 64 KB Ring Buffer: Bi-directional buffer to prevent overruns under high baud rates.
- Crash-Resistant: Runs under UMDF 2.0 in user space; cannot crash the Windows kernel.
- Dynamic Device Management: Add, query, and remove ports at runtime via Windows SetupAPI and CfgMgr32.
- Management Options: WPF desktop interface (with English/Chinese localization) and scriptable console CLI.
Download the installer package from Releases:
- Installer (
VSerial-Setup-v1.0.0-x64.exe): Installs the driver, desktop app, and configures systemPATH.
Note: Releases only provide the installer package. If you require a portable standalone zip, build it from source using
pwsh -File .\scripts\build_release.ps1 -BuildPortable.
Note: Hardware management requires an elevated terminal (Run as Administrator).
vserial.exe pair add --id 1 --portA COM10 --portB COM11vserial.exe pair listvserial.exe pair remove --id 1A Python test script is available in tests/test_serial_pair.py:
pip install pyserial
python tests/test_serial_pair.py --portA COM10 --portB COM11The script verifies:
- Bidirectional full-duplex text transmission
- 64 KB binary throughput and MD5 integrity
- RTS/CTS and DTR/DSR flow control state transitions
- Visual Studio 2022 (v143 toolset with Spectre-mitigated libs)
- Windows SDK & WDK:
10.0.26100.0 - .NET 8.0 SDK
- Inno Setup 6 (optional, for installer build)
# Default: build driver, publish CLI/GUI, and create installer package
pwsh -File .\scripts\build_release.ps1
# Include portable zip package:
pwsh -File .\scripts\build_release.ps1 -BuildPortable
# Custom version override (defaults to Directory.Build.props):
pwsh -File .\scripts\build_release.ps1 -Version 2.1.0Artifacts are placed in the dist/ directory.