Before diving into code, familiarize yourself with Intercom’s API documentation to understand how to authenticate and fetch data. Similarly, review Google Pub/Sub documentation to understand how to publish messages to a topic.

Create a Google Cloud Platform (GCP) account if you haven't already. In the Google Cloud Console, create a new project, enable the Pub/Sub API, and create a Pub/Sub topic where you will publish your data from Intercom.

In your Intercom account, navigate to the Developer Hub and create a new app. Generate an access token to authenticate requests from your server to Intercom’s API. This token will be used in the header of your API requests to fetch data.

Write a script or program using a programming language of your choice (such as Python, Node.js, or Java) to send HTTP requests to Intercom’s API endpoints. Use the access token for authentication. For instance, to fetch user data, send a GET request to `https://api.intercom.io/users`.

Once you receive the data from Intercom, process and format it as needed for your application. This might involve transforming JSON data, filtering specific fields, or aggregating information before sending it to Google Pub/Sub.

Generate a service account key in Google Cloud Console and download the JSON credentials file. In your script, authenticate your application with these credentials using Google's client libraries. Set the `GOOGLE_APPLICATION_CREDENTIALS` environment variable to point to your credentials file.

Use Google Cloud’s client libraries to write a function in your script that publishes the processed Intercom data to your Pub/Sub topic. Ensure that you handle any exceptions or errors during the publishing process. Here's a basic example in Python:

```python
from google.cloud import pubsub_v1
import json

# Initialize a Publisher client
publisher = pubsub_v1.PublisherClient()
topic_path = publisher.topic_path('your-project-id', 'your-topic-name')

def publish_message(data):
# Convert data to JSON string and encode it to bytes
data_str = json.dumps(data)
data_bytes = data_str.encode('utf-8')
# Publish the message
future = publisher.publish(topic_path, data=data_bytes)
print(f'Published message ID: {future.result()}')

# Example usage
intercom_data = {"example_key": "example_value"}
publish_message(intercom_data)
```

By following these steps, you can move data from Intercom to Google Pub/Sub without relying on third-party connectors or integrations. Adjust your scripts to handle specific data types and ensure robust error handling for a reliable data transfer process.