RJ45 Sound Card

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🌐 Website: https://devfrp.github.io/RJ-45-SOUND-CARD/

Share any sound card between two PCs over Ethernet (RJ45).

The server PC (with the physical sound card, e.g. MOTU, RME, Focusrite...) captures audio and streams it over the network. The client PC (laptop) receives the stream and plays it through a virtual audio device, making the remote sound card accessible as if it were local.

Architecture

┌─────────────────────────┐       RJ45 (Ethernet)        ┌──────────────────────────┐
│  SERVER (Studio PC)     │◄──────────────────────────►│  CLIENT (Laptop)          │
│                         │  UDP: audio stream (port 42001)│                         │
│  Physical sound card    │  TCP: control     (port 42002)│  Virtual Audio Device    │
│  (MOTU, RME, …)         │  UDP: discovery   (port 42000)│  (snd-aloop/BlackHole/  │
│                         │                               │   VB-Cable)              │
│  Capture → UDP Send     │                               │  UDP Receive → Playback  │
│  UDP Receive → Playback │                               │  Capture → UDP Send      │
└─────────────────────────┘                               └──────────────────────────┘

Features

• Cross-platform: Windows, Linux, macOS
• All sound cards: compatible with any audio device recognized by the OS (MOTU, RME, Focusrite, Universal Audio, Presonus, etc.)
• Bidirectional: server → client audio AND client → server audio
• Low latency: UDP streaming with configurable buffers (64–1024 frames)
• Jitter buffer: packet reordering and jitter compensation for smooth playback
• Encryption: optional pre-shared key encryption and authentication
• Integer PCM: f32, i16, i24, i32 sample formats with automatic conversion
• Auto-discovery: the client automatically finds servers on the network
• Auto-detect virtual device: finds Loopback, BlackHole, or VB-Cable automatically
• Remote control: volume, device selection, status
• Multi-channel: supports 1 to 64+ channels depending on configuration
• Multi-client: server supports multiple simultaneous client connections
• Daemon mode: run as a background service with --daemon flag or systemd

Installation

Prerequisites

• Rust (to compile): curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
• PortAudio (audio library):
  • Linux: sudo apt install libasound2-dev (or pulseaudio, jack)
  • macOS: already included with CoreAudio
  • Windows: already included with WASAPI

Compilation

git clone https://github.com/devfrp/RJ-45-SOUND-CARD.git
cd RJ-45-SOUND-CARD
cargo build --release
./target/release/rjsc --help

The rjsc binary is self-contained and can be copied to any machine running the same OS.

Virtual Audio Device Setup (CLIENT)

So the client PC sees the remote sound card as a local device:

Linux:

sudo ./scripts/linux_setup.sh install

macOS:

sudo ./scripts/mac_setup.sh install

Windows (Administrator PowerShell):

powershell -ExecutionPolicy Bypass -File scripts\windows_setup.ps1 install

Usage

1. List available audio devices

# On the server (PC with the sound card)
rjsc list

# On the client (laptop)
rjsc list

2. Configure

Create a configuration file and edit it:

rjsc init

Example configuration (rjsc.toml):

[audio]
input_device = "MOTU 424"      # Example: your device name
output_device = "MOTU 424"     # Example: your device name
channels = 8                   # Number of channels to share
sample_rate = 48000            # Sample rate
buffer_frames = 256            # Buffer size (latency)

[network]
audio_port = 42001
control_port = 42002
bind_address = "0.0.0.0"

[client]
use_virtual_device = true
virtual_device_name = "hw:Loopback,0,0"  # Linux
# virtual_device_name = "BlackHole 16ch"  # macOS
# virtual_device_name = "CABLE Input (VB-Audio Virtual Cable)"  # Windows
auto_reconnect = true

3. Server (PC with the physical sound card)

# On the studio machine (with the physical sound card)
rjsc serve

4. Client (laptop)

# Auto-connect (network discovery)
rjsc connect

# Or with a specific address
rjsc connect --server 192.168.1.100:42002

Latency

Latency depends on:

• Buffer size: 64 frames → ~1.3ms, 256 → ~5.3ms, 1024 → ~21ms (at 48kHz)
• Network: Ethernet switch/router latency
• Audio drivers: ASIO (Windows) / JACK (Linux) offer the lowest latency

For real-time monitoring, use 64 or 128 frames with a Gigabit network.

Troubleshooting

Client can't find the server:

• Make sure both PCs are on the same network
• Check firewall (open UDP ports 42000-42001, TCP port 42002)
• Use --server to specify the address manually

No sound on the client:

• Check the virtual audio device with rjsc list
• Check system sound settings (select the virtual device)
• Increase the buffer size

Latency too high:

• Reduce buffer_frames (64 or 128)
• Use a Gigabit network (not WiFi)
• Enable JACK (Linux) or ASIO (Windows) for low-latency drivers

License

MIT

Documentation

• Configuration reference — all rjsc.toml options
• Architecture — internal design and protocols
• Contributing — contribution guide
• Changelog — version history
• Man page — man rjsc
• English README