Echo DVC

Echo DVC is a simple yet functional Remote Desktop Protocol (RDP) plugin implemented using the Dynamic Virtual Channel (DVC) API. It currently supports Microsoft RDP and Citrix.

The goal of this project is to provide a template for building RDP DVC plugins in Rust, covering both client and server sides. While the echo functionality is minimal, it serves as a useful and lightweight implementation to validate DVC communication.

Under the hood, the client plugin is implemented as a COM object. Because it uses COM technology, the plugin is only available on Windows.

⚙️ This project is ideal for developers looking to build and experiment with custom DVC plugins in Rust.

✨ Features

• RDP Dynamic Virtual Channel support
• Written in Rust
• COM-based client plugin for Windows
• Cross-compatibility with:
  • Citrix (Windows x86) — use x86 version
  • MSTSC (Microsoft Remote Desktop Connection) — use x64 version
• Simple echo server for basic data exchange testing

Installation

You can find in the Releases section the different binaries:

• DLL for the client
• executable for the server

Both have a 32 and 64 bits version depending on your target.

Use the 32bits version for Citrix and the 64bits for Windows.

Client side (Windows)

The client-side DLL must be registered via the Windows registry. For this purpose, the DLL exports DllRegisterServer and DllUnregisterServer, making it compatible with regsvr32.exe.

To register the plugin:

# 64bits registration
regsvr32.exe C:\Path\to\echo_dvc_plugin.dll

# 32bits registration
regsvr32.exe C:\Path\to\echo_dvc_plugin_32.dll

To unregister the plugin:

# 64bits
regsvr32.exe /u C:\Path\to\echo_dvc_plugin.dll

# 32bits
regsvr32.exe /u C:\Path\to\echo_dvc_plugin_32.dll

Server side

The server is a standalone executable that can be run on the remote machine once a remote session has been established.

Usage

Once the plugin is registered, connect to your favorite remote instance. If the plugin has been correctly installed, Remote Desktop Connection client should load it successfully.

From there, run the server binary. You should see the following prompt:

Usage:
- "write XXXX" or "put XXXX" to write to the DVC
- "quit" or "exit" to leave this interface

echo_dvc> 

💡 If you changed the plugin DVC name, you do not need to rebuild the server binary as you can override the DVC name on the commandline. Please see the help for further information on the usage: .\echo_dvc_server.exe --help

✅ Compatibility

Environment	Architecture	Compatible
Microsoft RDP (MSTSC)	x64	✅
Citrix Receiver	x86	✅

Make sure to build or use the correct DLL architecture according to your client.