First, ensure that the Google Cloud SDK is installed on the machine where Jenkins is running. This SDK will enable you to interact with Google Cloud services. Download and install the SDK from the [Google Cloud SDK website](https://cloud.google.com/sdk/docs/install). Once installed, authenticate the SDK by running `gcloud init` and follow the prompts to log in to your Google Cloud account.

In the Google Cloud Console, navigate to Pub/Sub. Create a new topic to which Jenkins will publish messages. This can be done by selecting "Create Topic" and providing a unique name for your topic. Make sure to note the topic name as it will be needed later.

Create a service account in Google Cloud Console with the necessary permissions to publish messages to the Pub/Sub topic. Go to the "IAM & Admin" section, select "Service Accounts," and create a new service account. Assign it the "Pub/Sub Publisher" role. Generate and download a JSON key for this service account, as Jenkins will use it to authenticate.

Ensure that the "Pipeline" plugin is installed in Jenkins, as it allows for the creation of Jenkins pipelines which can contain custom scripts. Go to "Manage Jenkins" -> "Manage Plugins" and install the "Pipeline" plugin if it is not already installed.

Create a Jenkins pipeline job that includes a script to publish data to Google Pub/Sub. The script should use the `gcloud` command-line tool to publish messages. Here is a basic example of a pipeline script:
```groovy
pipeline {
agent any
environment {
GOOGLE_APPLICATION_CREDENTIALS = ''
}
stages {
stage('Publish to Pub/Sub') {
steps {
script {
def message = 'Your message data'
sh "gcloud pubsub topics publish --message '${message}'"
}
}
}
}
}
```
Replace `` and `` with your specific file path and topic name.

Store your service account JSON key file securely on the Jenkins server. Use Jenkins credentials to handle sensitive information. Go to "Manage Jenkins" -> "Manage Credentials" to add a new credential for your service account key. In your pipeline script, reference this credential using Jenkins' environment variables.

Run the Jenkins pipeline to ensure that data is being successfully published to Google Pub/Sub. Monitor the logs in Jenkins to verify that the `gcloud` command executes without errors. You can also check the Google Cloud Console under Pub/Sub to confirm that messages are being received in the specified topic.

By following these steps, you can efficiently move data from Jenkins to Google Pub/Sub without relying on third-party connectors or integrations.