VIIPER

VIIPER 🐍

Virtual Input over IP EmulatoR

A cross-platform virtual USB input framework for creating virtual USB input devices (game controllers, keyboards, mice and more) that are indistinguishable from real hardware to the operating system and applications.

VIIPER lets developers create and programmatically control virtual USB input devices (using USBIP under the hood), enabling seamless integration for gaming, automation, testing and remote control scenarios.

• Runs on Linux and Windows.
• (Optional) network support built in: control devices over a network with lower overhead than raw USBIP alone.
• VIIPER abstracts away all USB / USBIP details.
• VIIPER is portable and runs entirely in userspace.
  • Utilizes a generic USBIP kernel mode driver
    (built into Linux; on Windows usbip-win2 provides a signed kernel mode driver)
    New device types never require touching kernel code.
• After installing USBIP once, VIIPER can run without additional dependencies or system-wide installation.

VIIPER comes in two distinct flavors:

• VIIPER server
  a self-contained, (no dependencies, statically linked) portable, standalone executable
  • exposing a lightweight TCP-API
  • control devices from any language or machine on the network
• libVIIPER
  a single shared library to embed device emulation directly into your application
  See Examples for C and C# here
  or the libVIIPER documentation for details and examples.

For why you should pick one over the other see the FAQ

Beyond device emulation, VIIPER can proxy real USB devices for traffic inspection and reverse engineering.

Emulatable devices:

• Xbox 360 controller emulation; see Devices › Xbox 360 Controller
• HID Keyboard with N-key rollover and LED feedback; see Devices › Keyboard
• HID Mouse with 5 buttons and horizontal/vertical wheel; see Devices › Mouse
• PS4 controller emulation; see Devices › DualShock 4 Controller
• PS5 DualSense controller emulation (including Edge variant); see Devices › DualSense Controller
• Nintendo Switch 2 Pro Controller emulation; see Devices › Switch 2 Pro Controller

🔌 Requirements

Linux:

• Arch Linux:

  • Install: sudo pacman -S usbip
  • Docs: Arch Wiki: USBIP

• Ubuntu:

  • Install: sudo apt install linux-tools-generic
  • Docs: Ubuntu USBIP Manual

Windows:

• usbip-win2 is by far the most complete implementation of USBIP for Windows (comes with a SIGNED kernel mode driver).

🥫 Feeder application development

You have two options for developing feeder applications that control the virtual devices created by VIIPER:

• Use the standalone VIIPER server and interface via the exposed TCP-API (preferably using one of the available client libraries)
• Integrate libVIIPER directly into your application.
  See Examples for examples in either C or C#.

🔌 API

VIIPER includes a lightweight TCP based API for device and bus management, as well as streaming device control.
It's designed to be trivial to drive from any language that can open a TCP socket and send null-byte-terminated commands.

[!TIP] Most of the time, you don't need to implement that raw protocol yourself, as client libraries are available.
See Client Libraries.

• The TCP API uses a string-based request/response protocol terminated by null bytes (\0) for device and bus management.
  • Requests have a "path" and optional payload (sometimes JSON).
    eg. bus/{id}/add {"type": "keyboard", "idVendor": "0x6969"}\0
  • Responses are often JSON as well!
  • Errors are reported using JSON objectes similar to RFC 7807 Problem Details
    ^{The use of JSON allows for future extenability without breaking compatibility ;)}
• For controlling, or feeding, a device a long lived TCP stream is used, with a wire-protocol specific to each device type.
  After an initial "handshake" (bus/{busId}/{deviceId}\0) a device-specific binary protocol is used to send input reports and receive output reports (e.g., rumble commands).

VIIPER takes care of all USBIP protocol details, so you can focus on implementing the device logic only.
On localhost VIIPER also automatically attached the USBIP client, so you don't have to worry about USBIP details at all.

See the API documentation for details

🛠️ VIIPER development

🧰 Prerequisites

• Go 1.26 or newer
• USBIP installed
• (Optional) just
  • Windows: winget install --id Casey.Just --exact
  • Linux/macOS: cargo install just or use your package manager
• Windows compiler (required for build-libVIIPER):
  • winget install -e --id MartinStorsjo.LLVM-MinGW.UCRT --accept-package-agreements --accept-source-agreements

🔄 Building from Source

git clone https://github.com/Alia5/VIIPER.git
cd VIIPER
just build Release

The binary will be in dist/viiper-<goos>-<goarch> (for example dist/viiper-windows-amd64.exe).

For more build options:

just --list            # Show all available targets
just test              # Run tests

🤝 Contributing

Contributions are welcome!
Please open issues or pull requests on GitHub.
See the issues page for bugs and feature requests.

❓ FAQ

What is USBIP and why does VIIPER use it?

USBIP is a protocol that allows USB devices to be shared over a network.
VIIPER uses it because it's already built into Linux and available for Windows, making virtual device emulation possible without writing custom kernel drivers yourself.

Why choose the the standalone executable and interfacing via TCP over, and the (shared-object) libVIIPER library

• Flexibility
  • allows one to use VIIPER as a service on the same host as the USBIP-Client and use the feeder on a different, remote machine.
  • allows for software written utilizing VIIPER to not be licensed under the terms of the GPLv3
  • Allows users to idenpendently update VIIPER to receive updates and bugfixes without affecting other components or having to recompile applications themselves.
    This also takes away maintenance burdens for feeder-application developers (likely you)

Can I use VIIPER for gaming?

Yes! VIIPER can create virtual input devices that appear as real hardware to games and applications.
This works with Steam, native Windows games and any other application that supports the emulated device types.

How is VIIPER different from other controller emulators?

Many controller emulation approaches require writing a custom kernel driver for every device type you want to support.
VIIPER uses USBIP to handle the USB protocol layer, so device emulation code lives entirely in userspace.

USBIP itself does require a kernel driver.
On Linux, the USBIP driver is built into the kernel.
On Windows, usbip-win2 provides a signed kernel mode driver.
That driver is generic and does not need to know anything about specific device types.
All device-type logic stays in userspace.

This makes VIIPER portable, easier to extend and simpler to bundle with applications.
Adding a new device type never requires touching kernel code.

Can I add support for other device types?

Yes! VIIPER's architecture is designed to be extensible.
Check the xbox360 device implementation as a reference for creating new device types.

You mentioned proxying USBIP?

VIIPER as a proxy mode that sits between a USBIP client and a USBIP server (like a Linux machine sharing real USB devices).
THis intercepts and logs all URBs passing through, without handling the devices directly.
Useful for reverse engineering USB protocols and understanding how devices communicate.

What about TCP overhead or input latency performance?

End-to-end input latency for virtual devices created with VIIPER could be typically well below 1 millisecond on a modern desktop (e.g. Windows / Ryzen 3900X test machine).
Detailed methodology and sample runs can be found in E2E Latency Benchmarks.
However, to not stress the CPU excessively, reports get batched and sent every millisecond. So the best you will achive is a 1000Hz update rate, which is more than enough and more than what most real hardware devices provide.
Note: Actual device polling rates may be lower depending on the device type and configuration.

📄 License

VIIPER - Virtual Input over IP EmulatoR

Copyright (C) 2025-2026 Peter Repukat

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.

Credits / Inspiration

• REDACTED-Bus aka ViGEmBus
  (Retired, but still widely used) Windows kernel-mode driver emulating well-known USB game controllers
  Shoutout and thank you to @nefarius for paving the way and always being a super decent guy!
• Valve Software
  For creating the OG Steam Controller (2015) and Steam Input (and the way it, understandably, works...)
  that sent me down this rabbit hole in the first place
  ^{I kinda hate you guys... in good way(?) ;)}
• USBIP without VIIPER would not be possible.
  • USBIP
  • USBIP-Win2
• SDL
  For their excellent work on input device handling, reducing reversing efforts to a minimum.