CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Build Commands

# Build server and client binaries
go build -o server ./cmd/server
go build -o client ./cmd/client

# Run server (zero-config, auto-generates token and TLS cert)
./server
./server -c server.yaml  # with config file

# Run client
./client -s <server>:7000 -t <token> -id <client-id>
./client -s <server>:7000 -t <token> -id <client-id> -no-tls  # disable TLS

# Web UI development (in web/ directory)
cd web && npm install && npm run dev    # development server
cd web && npm run build                  # production build (outputs to web/dist/)

Architecture Overview

GoTunnel is an intranet penetration tool (similar to frp) with server-centric configuration - clients require zero configuration and receive mapping rules from the server after authentication.

Core Design

Yamux Multiplexing: Single TCP connection carries both control (auth, config, heartbeat) and data channels
Binary Protocol: [Type(1 byte)][Length(4 bytes)][Payload(JSON)] - see pkg/protocol/message.go
TLS by Default: Auto-generated self-signed ECDSA P-256 certificates, no manual setup required
Embedded Web UI: Vue.js SPA embedded in server binary via //go:embed

Package Structure

cmd/server/          # Server entry point
cmd/client/          # Client entry point
internal/server/
  ├── tunnel/        # Core tunnel server, client session management
  ├── config/        # YAML configuration loading
  ├── db/            # SQLite storage (ClientStore interface)
  ├── app/           # Web server, SPA handler
  ├── router/        # REST API endpoints
  └── plugin/        # Server-side plugin manager
internal/client/
  ├── tunnel/        # Client tunnel logic, auto-reconnect
  └── plugin/        # Client-side plugin manager and cache
pkg/
  ├── protocol/      # Message types and serialization
  ├── crypto/        # TLS certificate generation
  ├── proxy/         # Legacy proxy implementations
  ├── relay/         # Bidirectional data relay (32KB buffers)
  ├── utils/         # Port availability checking
  └── plugin/        # Plugin system core
      ├── types.go       # ProxyHandler interface, PluginMetadata
      ├── registry.go    # Plugin registry
      ├── builtin/       # Built-in plugins (socks5, http)
      ├── wasm/          # WASM runtime (wazero)
      └── store/         # Plugin persistence (SQLite)
web/                 # Vue 3 + TypeScript frontend (Vite)

Key Interfaces

ClientStore (internal/server/db/): Database abstraction for client rules storage
ServerInterface (internal/server/router/): API handler interface
ProxyHandler (pkg/plugin/): Plugin interface for proxy handlers
PluginStore (pkg/plugin/store/): Plugin persistence interface

Proxy Types

内置类型 (直接在 tunnel 中处理):

TCP (default): Direct port forwarding (remote_port → local_ip:local_port)
UDP: UDP port forwarding
HTTP: HTTP proxy through client network
HTTPS: HTTPS proxy through client network

插件类型 (通过 plugin 系统提供):

SOCKS5: Full SOCKS5 protocol (official plugin)

Data Flow

External User → Server Port → Yamux Stream → Client → Local Service

Configuration

Server: YAML config + SQLite database for client rules
Client: Command-line flags only (server address, token, client ID)
Default ports: 7000 (tunnel), 7500 (web console)

Plugin System

GoTunnel supports a WASM-based plugin system for extensible proxy handlers.

Plugin Architecture

内置类型: tcp, udp, http, https 直接在 tunnel 代码中处理
Official Plugin: SOCKS5 作为官方 plugin 提供
WASM Plugins: 自定义 plugins 可通过 wazero 运行时动态加载
Hybrid Distribution: 内置 plugins 离线可用；WASM plugins 可从服务端下载

ProxyHandler Interface

type ProxyHandler interface {
    Metadata() PluginMetadata
    Init(config map[string]string) error
    HandleConn(conn net.Conn, dialer Dialer) error
    Close() error
}

Creating a Built-in Plugin

See pkg/plugin/builtin/socks5.go as reference implementation.

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