# CustomTransportStrategy

**Kind:** Interface

**Source:** [`packages/microservices/interfaces/custom-transport-strategy.interface.ts`](https://github.com/nestjs/nest/blob/master/packages/microservices/interfaces/custom-transport-strategy.interface.ts#L6)

**Part of:** [Microservices](subsystem-packages-microservices)

`CustomTransportStrategy` identifies a custom microservice transport implementation through its `transportId`. It is used by the microservices layer to distinguish custom transport strategies from built-in transports and route configuration or lifecycle handling to the correct implementation.

## Properties

| Property | Type |
|---|---|
| `transportId` | `TransportId` |

## Diagram

```mermaid
graph LR
  App[Application Configuration] --> Strategy[CustomTransportStrategy]
  Strategy --> TransportId[transportId: TransportId]
  TransportId --> CustomTransport[Custom Transport Implementation]
  CustomTransport --> Microservice[Microservice Runtime]
```

## Usage

```ts
import { CustomTransportStrategy } from '@nestjs/microservices';
import { Transport } from '@nestjs/microservices/enums/transport.enum';

class RedisStreamsTransportStrategy implements CustomTransportStrategy {
  transportId = Transport.REDIS;

  listen(callback: () => void) {
    // Start the custom transport server.
    callback();
  }

  close() {
    // Release transport resources.
  }
}

const strategy = new RedisStreamsTransportStrategy();

// Pass the strategy to your microservice configuration as needed.
console.log(strategy.transportId);
```

## AI Coding Instructions

- Implement `transportId` with the `TransportId` value that uniquely identifies the custom transport.
- Keep the identifier stable; changing it can break transport selection and configuration lookup.
- Use this interface alongside the required custom server or client transport strategy interfaces when implementing runtime behavior.
- Ensure the custom transport's lifecycle methods, such as startup and shutdown, are handled by the associated strategy implementation.