If my understanding is correct, you have created a data source connection to a database inside the Virtual DataPort server, and when you try to connect, it fails with the mentioned error message.
Generally, “Unknown host specified” error happens when the Denodo Virtual DataPort server is not able to reach the host where the data source is located. You may refer to this answer in the community [Unable to establish connection: IO Error: Unknown host specified](https://community.denodo.com/answers/question/details?questionId=9064u000000CfHuAAK&title=Unable+to+establish+connection%3A+IO+Error%3A+Unknown+host+specified) to help you troubleshoot the problem.
You can also refer to the documentation [Creating Data Sources and Base Views](https://community.denodo.com/docs/html/browse/8.0/en/vdp/administration/creating_data_sources_and_base_views/creating_data_sources_and_base_views) to learn more about how to create and configure various types of data sources.
Hope this helps!