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# Network Configuration
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Network setup utilities for React Native development, including Metro bundler port forwarding and reverse proxy configuration for device connectivity.
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## Capabilities
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### ADB Reverse Port Forwarding
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Sets up reverse port forwarding to allow Android devices to connect to the Metro development server running on the development machine.
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```typescript { .api }
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/**
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 * Set up reverse port forwarding for Metro bundler
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 * Runs 'adb reverse tcp:8081 tcp:8081' to allow loading the JS bundle from the packager
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 * @param packagerPort - Port number where Metro bundler is running
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 * @param device - Optional specific device identifier for reverse forwarding
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 */
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function tryRunAdbReverse(packagerPort: number | string, device?: string | void): void;
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```
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**Usage Examples:**
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```typescript
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import { tryRunAdbReverse } from "@react-native-community/cli-platform-android";
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// Set up reverse forwarding for default Metro port
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tryRunAdbReverse(8081);
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// Set up reverse forwarding for custom port
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tryRunAdbReverse(8082);
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// Set up reverse forwarding for specific device
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tryRunAdbReverse(8081, "emulator-5554");
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// Use string port number
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tryRunAdbReverse("8081");
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```
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## Network Configuration Details
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### Port Forwarding Mechanism
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The `tryRunAdbReverse` function establishes a reverse TCP connection that allows Android devices and emulators to access the Metro development server running on the host machine. This is essential for React Native development as it enables:
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- **Hot Reloading**: Live updates during development
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- **Remote Debugging**: DevTools integration
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- **Bundle Loading**: JavaScript bundle serving from Metro
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- **WebSocket Connection**: Real-time communication between device and Metro
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### Default Port Configuration
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By default, React Native's Metro bundler runs on port 8081. The reverse port forwarding maps:
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- Device port 8081 → Host port 8081
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This allows React Native apps running on Android devices to access `http://localhost:8081` and reach the Metro server on the development machine.
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### Error Handling
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The function includes built-in error handling for common scenarios:
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- **ADB not found**: Gracefully handles missing ADB installation
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- **Device not connected**: Handles disconnected or unavailable devices  
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- **Port already in use**: Manages port conflicts
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- **Permission issues**: Handles ADB permission problems
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**Important Notes:**
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- This function is automatically called by the `run-android` command
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- Manual invocation is useful for custom development setups
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- The reverse forwarding persists until the device is disconnected or ADB server restarts
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- Multiple devices can have reverse forwarding configured simultaneously