Network Relay (Subway-Sim)

A high-performance kernel-level network chaos simulator for Windows that allows you to test how your applications behave under poor network conditions like high latency, packet loss, and jitter.

Built with Rust, Tokio, and WinDivert, network-relay intercepts local network traffic in real-time to simulate real-world scenarios such as riding a subway, being in an elevator, or using a spotty 3G connection.

Features

• Real-time Interception: Uses WinDivert to capture and manipulate packets at the kernel level.
• Predefined Profiles: Quickly switch between common "bad network" scenarios:
  • subway: Spotty connection with 800ms latency and 10% packet loss.
  • elevator: Near dead-zone with 2.5s latency and 20% loss.
  • mountain: High-altitude latency (4s) with 5% loss.
  • 3g: Standard slow mobile network (400ms latency, 2% loss).
  • chaos: Extreme jitter (1500ms latency, 35% packet loss).
• Customizable: Override profile defaults with your own latency and drop rate values.
• TUI Dashboard: A live terminal interface showing packet statistics and network stability graphs.
• Multi-port Targeting: Automatically targets common development ports (8080, 3000, 8000, 5000) or a specific port of your choice.

Getting Started

Prerequisites

• Windows: This tool requires Windows for WinDivert support.
• Administrator Privileges: Packet interception requires running the terminal as an Administrator.

Installation

1. Clone the repository:

   git clone https://github.com/bhavukar/network-relay.git
   cd network-relay

2. Build the project:

   cargo build --release

Usage

Run the simulator with a specific profile (must be run as Administrator):

# Start with the default 'subway' profile
.\target\release\subway-sim.exe start

# Target a specific port with a custom profile
.\target\release\subway-sim.exe start --port 3000 --profile elevator

# Fully custom settings
.\target\release\subway-sim.exe start --port 8080 --latency 1500 --drop 15

Technical Stack

• WinDivert: Kernel-level packet interception.
• Ratatui: Terminal UI for live monitoring.
• Tokio: Asynchronous runtime for handling packet delays without blocking.
• Clap: Robust CLI argument parsing.

License

MIT © Bhavuk Arora