> ## Documentation Index
> Fetch the complete documentation index at: https://docs.streamnative.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Connect to Pulsar cluster using Node.js client

This document provides examples about how to use the Pulsar Node.js client to connect to a Pulsar cluster through a token or an OAuth2 credential file.

<Note title="Note">
  This document assumes that you have created a service account, and have granted the service account `produce` and `consume` permissions to the namespace for the target topic.
</Note>

## Connect to a Pulsar cluster using a token

This section describes how to connect to you Pulsar cluster using a token.

### Prerequisites

* [Get the service URL](/private-cloud/v1/build/connect-prepare#get-the-service-url).
* [Get a service account token](/private-cloud/v1/build/connect-prepare#get-a-service-account-token).

### Steps

To connect to your Pulsar cluster using a token, follow these steps.

1. Connect to the Pulsar cluster.

   ```javascript theme={null}
   const Pulsar = require('pulsar-client')
   const auth_params = process.env.AUTH_PARAMS
   const service_url = process.env.SERVICE_URL

   ;(async () => {
     const auth = new Pulsar.AuthenticationToken({
       token: 'AUTH_PARAMS',
     })

     // Create a client
     const client = new Pulsar.Client({
       serviceUrl: 'your-service-url',
       authentication: auth,
       operationTimeoutSeconds: 30,
     })

     await client.close()
   })()
   ```

   Set the `serviceUrl` and `token` parameters based on the descriptions in the [prepare to connect to a Pulsar cluster](/private-cloud/v1/build/connect-prepare) user guide.

2. Create a Node.js consumer and use the Node.js consumer to consume messages.

   ```javascript theme={null}
   const Pulsar = require('pulsar-client')
   const auth_params = process.env.AUTH_PARAMS
   const service_url = process.env.SERVICE_URL

   ;(async () => {
     const auth = new Pulsar.AuthenticationToken({
       token: 'AUTH_PARAMS',
     })

     // Create a consumer
     const consumer = await client.subscribe({
       topic: 'your-topic',
       subscription: 'your-sub-name',
       subscriptionType: 'Shared',
       ackTimeoutMs: 10000,
     })

     // Receive messages
     for (let i = 0; i < 10; i += 1) {
       const msg = await consumer.receive()
       console.log(msg.getData().toString())
       await consumer.acknowledge(msg)
     }

     await consumer.close()
     await client.close()
   })()
   ```

3. Create a Node.js producer and use the Node.js producer to produce messages.

   ```javascript theme={null}
   const Pulsar = require('pulsar-client')
   const auth_params = process.env.AUTH_PARAMS
   const service_url = process.env.SERVICE_URL

   ;(async () => {
     const auth = new Pulsar.AuthenticationToken({
       token: 'AUTH_PARAMS',
     })

     const producer = await client.createProducer({
       topic: 'your-topic',
       sendTimeoutMs: 30000,
       batchingEnabled: true,
     })

     // Send messages
     for (let i = 0; i < 10; i += 1) {
       const msg = `my-message-${i}`
       producer.send({
         data: Buffer.from(msg),
       })
       console.log(`Sent message: ${msg}`)
     }
     await producer.flush()

     await producer.close()
     await client.close()
   })()
   ```

## Connect to a Pulsar cluster using an OAuth2 credential file

To connect to your Pulsar cluster using an OAuth2 credential file, follow these steps.

1. Generate the App credentials by following similar instructions in [configure OAuth2 authentication](/private-cloud/v1/operating-streamnative-platform/security/oauth2-auth).

2. Save the App credentials into an OAuth2 credential file.

3. Connect to a Pulsar cluster through the OAuth2 credential file.

   ```javascript theme={null}
   const Pulsar = require('pulsar-client')
   const issuer_url = process.env.ISSUER_URL
   const private_key = process.env.PRIVATE_KEY
   const audience = process.env.AUDIENCE
   const scope = process.env.SCOPE
   const service_url = process.env.SERVICE_URL
   const client_id = process.env.CLIENT_ID
   const client_secret = process.env.CLIENT_SECRET

   ;(async () => {
     const params = {
       issuer_url: 'your-issuer-url',
     }
     if (private_key.length > 0) {
       params['private_key'] = 'file:///path/to/private-key-file.json'
     } else {
       params['client_id'] = 'your-client-id'
       params['client_secret'] = 'your-client-secret'
     }
     if (audience.length > 0) {
       params['audience'] = 'your-audience'
     }
     if (scope.length > 0) {
       params['scope'] = 'your-scope'
     }
     const auth = new Pulsar.AuthenticationOauth2(params)
     // Create a client
     const client = new Pulsar.Client({
       serviceUrl: 'pulsar-service-url',
       tlsAllowInsecureConnection: true,
       authentication: auth,
     })
     await client.close()
   })()
   ```

   * `issuer_url`: the URL of your OAuth2 identity provider.
   * `private_key`: the path to your OAuth2 credential file.
   * `client_id`: the Pulsar application client ID.
   * `client_secret`: the Pulsar application client secret.
   * `audience`: the `audience` of your Pulsar cluster.
   * `serviceUrl`: the URL of your Pulsar cluster.

4. Create a Node.js consumer and use the Node.js consumer to consume messages.

   ```javascript theme={null}
   const Pulsar = require('pulsar-client')
   const issuer_url = process.env.ISSUER_URL
   const private_key = process.env.PRIVATE_KEY
   const audience = process.env.AUDIENCE
   const scope = process.env.SCOPE
   const service_url = process.env.SERVICE_URL
   const client_id = process.env.CLIENT_ID
   const client_secret = process.env.CLIENT_SECRET

   ;(async () => {
     const params = {
       issuer_url: 'your-issuer-url',
     }
     if (private_key.length > 0) {
       params['private_key'] = 'file:///path/to/private-key-file.json'
     } else {
       params['client_id'] = 'your-client-id'
       params['client_secret'] = 'your-client-secret'
     }
     if (audience.length > 0) {
       params['audience'] = 'your-audience'
     }
     if (scope.length > 0) {
       params['scope'] = 'your-scope'
     }
     const auth = new Pulsar.AuthenticationOauth2(params)

     const consumer = await client.subscribe({
       topic: 'your-topic',
       subscription: 'your-sub-name',
       subscriptionType: 'Shared',
       ackTimeoutMs: 10000,
     })
     // Receive messages
     for (let i = 0; i < 10; i += 1) {
       const msg = await consumer.receive()
       console.log(msg.getData().toString())
       await consumer.acknowledge(msg)
     }
     await consumer.close()
     await client.close()
   })()
   ```

5. Create a Node.js producer and use the Node.js producer to produce messages.

   ```javascript theme={null}
   const Pulsar = require('pulsar-client')
   const issuer_url = process.env.ISSUER_URL
   const private_key = process.env.PRIVATE_KEY
   const audience = process.env.AUDIENCE
   const scope = process.env.SCOPE
   const service_url = process.env.SERVICE_URL
   const client_id = process.env.CLIENT_ID
   const client_secret = process.env.CLIENT_SECRET

   ;(async () => {
     const params = {
       issuer_url: 'your-issuer-url',
     }
     if (private_key.length > 0) {
       params['private_key'] = 'file:///path/to/private-key-file.json'
     } else {
       params['client_id'] = 'your-client-id'
       params['client_secret'] = 'your-client-secret'
     }
     if (audience.length > 0) {
       params['audience'] = 'your-audience'
     }
     if (scope.length > 0) {
       params['scope'] = 'your-scope'
     }
     const auth = new Pulsar.AuthenticationOauth2(params)

     const producer = await client.createProducer({
       topic: 'your-topic',
       sendTimeoutMs: 30000,
       batchingEnabled: true,
     })
     // Send messages
     for (let i = 0; i < 10; i += 1) {
       const msg = `my-message-${i}`
       producer.send({
         data: Buffer.from(msg),
       })
       console.log(`Sent message: ${msg}`)
     }
     await producer.flush()
     await producer.close()
     await client.close()
   })()
   ```