Error "IO Error: The Network Adapter could not establish the connection" When Connecting to Oracle

Published: 11 Nov 2020
Last Modified Date: 24 Aug 2022


When connecting Tableau Desktop to an Oracle database using one-way SSL and embedding the certificate in the workbook, the following error may occur:

IO Error: The Network Adapter could not establish the connection
Unable to connect to the Oracle server "<server>". Check that the server is running and that you have access privileges to the requested database.

Additionally, the following error is found in jprotocolserver.log in the Tableau Desktop logs folder:

Short read of DER length


  • Tableau Desktop 2020.3
  • Oracle
  • One-way SSL


To troubleshoot this issue, carry out the following steps:
  1. Open the server certificate file in a text editor, such as Notepad.
  2. Delete all of the text except the blocks of text starting with  "-----BEGIN CERTIFICATE-----" and ending with "-----END CERTIFICATE-----".
  3. Save the file with a different name.
  4. Use this new file as the custom SSL certificate file in the Oracle connector in Tableau Desktop.

If the above steps do not resolve the issue, contact the Oracle database administrator, who should be able to provide you with the correct server certificate file.


The certificate file is not in the expected format.
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