SimpleSocks5Proxy

A high-performance SOCKS5 proxy server implementation written in C# using .NET 9.

Overview

SimpleSocks5Proxy is a lightweight, efficient SOCKS5 proxy server that implements the SOCKS5 protocol as specified in RFC 1928. The server is designed for high performance with support for concurrent connections, asynchronous I/O operations, and structured logging.

Features

• SOCKS5 Protocol Compliance: Full implementation of RFC 1928 SOCKS5 protocol
• TCP CONNECT Support: Handles TCP streaming connections
• Multi-Address Support: IPv4, IPv6, and domain name resolution
• High Performance: Asynchronous I/O operations for scalability
• Concurrent Connections: Efficient handling of multiple simultaneous connections
• Configurable: JSON-based configuration with command-line overrides
• Structured Logging: Comprehensive logging using Serilog
• Graceful Shutdown: Proper handling of shutdown signals (Ctrl+C)
• Cross-Platform: Built on .NET 9 for cross-platform compatibility

Requirements

• .NET 9 Runtime
• Windows, Linux, or macOS

Configuration

The proxy server can be configured using JSON configuration files.

Default Configuration

The server looks for configuration in the following order:

1. Command-line specified configuration file
2. proxy.json in the application directory
3. appsettings.json for logging configuration

Proxy Configuration (proxy.json)

{
  "ListenIPAddress": "127.0.0.1",
  "ListenPort": 1080,
  "MaxConnections": 1000
}

Configuration Options:

• ListenIPAddress: IP address to bind the proxy server (default: 127.0.0.1)
• ListenPort: Port number to listen on (default: 1080)
• MaxConnections: Maximum number of concurrent connections, or 0 for unlimited (default: 1000)

Logging Configuration (appsettings.json)

{
  "Serilog": {
    "MinimumLevel": {
      "Default": "Information",
      "Override": {
        "Microsoft.AspNetCore": "Warning"
      }
    },
    "WriteTo": [
      {
        "Name": "Console",
        "Args": {
          "outputTemplate": "[{Timestamp:HH:mm:ss} {Level:u3}] {Message:lj}{NewLine}{Exception}"
        }
      }
    ]
  }
}

Usage

Basic Usage

Start the proxy server with default configuration:

dotnet run --project Socks5Proxy

Custom Configuration

Start with a custom configuration file:

dotnet run --project Socks5Proxy -- --config /path/to/custom-config.json

Command Line Arguments

• --config <path>: Specify custom configuration file path

Client Configuration

Configure your applications to use the SOCKS5 proxy:

• Proxy Host: 127.0.0.1 (or configured listen address)
• Proxy Port: 1080 (or configured listen port)
• Proxy Type: SOCKS5
• Authentication: None

Architecture

The application consists of several key components:

• Program.cs: Main entry point and application lifecycle management
• Server.cs: Core SOCKS5 server implementation
• ConnectionHandler.cs: Handles individual client connections
• Socks5Protocol.cs: SOCKS5 protocol implementation and message parsing
• UdpRelay.cs: UDP relay functionality (future enhancement)
• ProxyConfiguration.cs: Configuration management

Protocol Support

Supported Features

• SOCKS5 protocol (RFC 1928)
• TCP CONNECT command
• UDP ASSOCIATE command
• IPv4 addresses
• IPv6 addresses
• Domain name resolution
• No authentication method (0x00)

Currently Not Supported

• SOCKS4/SOCKS4a protocols
• BIND command
• Username/password authentication
• GSSAPI authentication

Performance

The server is optimized for high performance:

• Asynchronous I/O operations using async/await
• Efficient memory management
• Low-latency connection handling
• Scalable concurrent connection support

Project Structure

SimpleSocks5Proxy/
├── Documents/           # Project documentation
├── Socks5Proxy/        # Main application source code
│   ├── Program.cs      # Application entry point
│   ├── Server.cs       # SOCKS5 server implementation
│   ├── ConnectionHandler.cs
│   ├── Socks5Protocol.cs
│   ├── UdpRelay.cs
│   ├── ProxyConfiguration.cs
│   ├── appsettings.json
│   └── proxy.json
├── LICENSE             # License file
└── Socks5Proxy.sln    # Solution file

Friendly name logging

Optionally map specific IP addresses to human-friendly labels for clearer logs. When a mapping exists, logs append a suffix like (FriendlyName) after the IP or endpoint.

Example config (in proxy.json):

{
  "ListenIPAddress": "0.0.0.0",
  "ListenPort": 1080,
  "IPAddressMappings": [
    { "IPAddress": "192.168.1.10", "FriendlyName": "Laptop" },
    { "IPAddress": "10.0.0.5", "FriendlyName": "NAS" }
  ]
}

Log output:

• Before: New client connection from 192.168.1.10:51324
• After: New client connection from 192.168.1.10:51324 (Laptop)

If no mapping exists, the original value is logged unchanged. Domains (e.g., example.org:80) aren’t mapped.

License

This project is licensed under the terms specified in the LICENSE file.