Software⏱️ 3 min read📅 2026-06-15

How to Fix error code 335544721 Error – Connecting DBeaver to a Firebird file, gives error code 335544721

Error connecting to Firebird database file with DBeaver, unable to complete network request to host localhost SQLState:08006 ISC error code 335544721 Connection refused: connect

Quick Answer: Check if the Firebird server is running and configured correctly, ensure that the driver version is compatible with your Firebird version.

📋 Table of Contents

  1. 🛑 Root Causes of the Error
  2. 🛠️ Step-by-Step Verified Fixes
  3. 💡 Conclusion

The error code 335544721 is an ISC (InterServer Communications) error code, which indicates that the connection to the Firebird database file has been refused. This issue affects users who are trying to connect to a local Firebird database using DBeaver.

This error can be frustrating for database administrators and developers who need to inspect tables, perform queries, or report data from a Firebird database. In this guide, we will walk you through the troubleshooting steps to resolve this issue.

🛑 Root Causes of the Error

  • The primary reason for this error is that DBeaver is trying to connect to the local Firebird database file using a network protocol (TCP/IP) instead of the embedded protocol. This can be caused by the default configuration settings in DBeaver or the Firebird driver.
  • Another possible cause is that the Firebird server process is not running or not listening on the correct port.

🛠️ Step-by-Step Verified Fixes

Using the Embedded Protocol

  1. Step 1: Open DBeaver and go to Settings > Database > Advanced settings. In the 'JDBC connection' section, click on the 'Edit...' button next to the Firebird driver configuration.
  2. Step 2: In the 'Firebird JDBC Driver' properties window, ensure that the 'Protocol' field is set to 'Embeddable'. This will tell DBeaver to use the embedded protocol instead of TCP/IP.
  3. Step 3: Save the changes and try connecting to the database again.

Verifying Firebird Server Process

  1. Step 1: Start the Firebird server process manually by running the 'firebird-server' command in your terminal or command prompt. You can find the location of the executable file in the Firebird installation directory.
  2. Step 2: Verify that the server process is listening on the correct port (default is 54345) by using a tool like 'netstat' or 'ss' to check for active connections.
  3. Step 3: If the server process is not running, start it and try connecting to the database again after a few seconds.

💡 Conclusion

To resolve the error code 335544721 in DBeaver when trying to connect to a local Firebird database file, you can try using the embedded protocol or verifying that the Firebird server process is running and listening on the correct port. If none of these steps work, please refer to the Firebird documentation or seek further assistance from the DBeaver community or support team.

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