java.lang.IllegalStateException: transport client is closed

This exception is thrown when an operation is attempted on a closed transport client. In other words, the transport client has already been shut down and is no longer available for use.

To resolve this issue, you need to ensure that the transport client is opened before performing any operations on it. Additionally, you should make sure that the transport client is properly closed when it is no longer needed.

Here are some steps you can take to resolve this issue:

1. Check that the transport client is properly initialized before use. You can do this by calling the `isOpen()` method on the transport client.

2. If the transport client is not open, call the `open()` method to initialize it.

3. Make sure that the transport client is properly closed when it is no longer needed. You can do this by calling the `close()` method on the transport client.

4. If you are using multiple threads, ensure that the transport client is synchronized properly to prevent concurrent access.

By following these steps, you should be able to resolve the "transport client is closed" exception and use the transport client without any issues.