# ISocketFactoryArgs

**Kind:** Interface

**Source:** [`packages/microservices/external/kafka.interface.ts`](https://github.com/nestjs/nest/blob/master/packages/microservices/external/kafka.interface.ts#L76)

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

`ISocketFactoryArgs` defines the connection parameters provided when creating a Kafka socket. It groups the broker address, TLS configuration, and connection lifecycle callback required by the microservices Kafka transport.

## Properties

| Property | Type |
|---|---|
| `host` | `string` |
| `port` | `number` |
| `ssl` | `tls.ConnectionOptions` |
| `onConnect` | `() => void` |

## Diagram

```mermaid
graph LR
  SocketFactory[Kafka Socket Factory] --> Args[ISocketFactoryArgs]
  Args --> Host[host: string]
  Args --> Port[port: number]
  Args --> SSL[ssl: tls.ConnectionOptions]
  Args --> OnConnect[onConnect: () => void]
  SSL --> TLS[TLS-secured broker connection]
  OnConnect --> Ready[Connection established]
```

## Usage

```ts
import type { ConnectionOptions } from 'node:tls';

interface ISocketFactoryArgs {
  host: string;
  port: number;
  ssl: ConnectionOptions;
  onConnect: () => void;
}

const socketArgs: ISocketFactoryArgs = {
  host: 'kafka.example.com',
  port: 9093,
  ssl: {
    rejectUnauthorized: true,
    // ca, cert, and key can be provided when required by the broker.
  },
  onConnect: () => {
    console.log('Connected to Kafka broker');
  },
};

// Pass socketArgs to the Kafka transport socket factory.
```

## AI Coding Instructions

- Provide a valid Kafka broker hostname and port; use the TLS listener port when `ssl` is configured.
- Pass `tls.ConnectionOptions` through unchanged so certificate, key, CA, and verification settings remain available to the underlying socket.
- Use `onConnect` only for post-connection work, such as logging or readiness updates; avoid blocking operations.
- Do not place connection error handling in `onConnect`; handle socket and transport errors through the relevant Kafka client hooks.