Fixed IO bug: Network adapter could not connect to Oracle SQL

  • The network adapter failed to connect due to an incorrect URL, IP address, port, Service_Name, SID, and DNS.
  • Oracle SQL Developer is a free integrated development environment that simplifies the development and management of Oracle databases in both traditional and cloud environments.
  • It is very important that Serving the Listener is running in the background for the application to work properly.
  • To check if the listener is working or not, simply open a command prompt with administrator privileges and write :. lsnrctl status.
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To install Oracle 11g on a 64 bit Windows machine, the Oracle Universal Installation was used. A database was created using DBCA. SQLPlus is able to connect successfully to the database. 64 bit SQL Developers and applications that use ODBC are unable to connect. There is an error “Oracle .external.jdbc_12.2.1 cannot locate Oracle jdbc.driver.T4CDriverExtension” during SQL and Java applications.

Let’s ignore the tracing information for now. I have defined the SDU as 2M in the file. Notice how the directive appears immediately below the description. My tests do not seem to indicate that it affects the sid_list_listener part. It took me about 2 hours to research this…it’s quite disappointing to me now.

Choosing this page does not specify the e-mail address to which notifications will be sent. On the Preferences General page, you can specify that address (where notifications will be sent).

An incorrect URL, IP address, service name, service identification number (SID), or port number prevented the network adapter from connecting. Check your URL, IP address, port, Service_Name, SID, and DNS if you receive the Network Adapter failed to connect error. Check your database listener’s configuration if your URL, IP, port, Service_Name, or SID are correct.

There are multiple solutions to this problem, but I keep getting this error on SQL Developer version 20.2.0.175.1842.

It is a free integrated development environment for developing and managing Oracle databases in traditional and cloud environments. With SQL Developer, you can develop PL/SQL applications, execute queries and scripts with a worksheet, manage databases with a DBA console, generate reports, model data, and migrate third-party databases to Oracle with a migration platform.

What is the cause of the “Network adapter failed to connect” error?

What is the cause of the Network adapter failed to connect error

The Java application I’m using connects to the same Oracle Database. 

The following error message appears when I try to connect to anything. I am a beginner in Oracle SQL Developer, so I am posting this as a beginner:

We investigated the issue and found a set of solutions that will solve the problem completely, along with the reasons behind it.

  • Incorrect data: Make sure that the login information is entered correctly. The hostname, port, username, and password must be entered correctly for the connection to be established. An error may occur if any of these values are entered incorrectly.
  • Serving people with disabilities: It is very important that Serving the Listener is running in the background for the application to work properly. If it has not been started or disabled, this error may be caused.

To avoid conflicts, make sure you implement them in a specific way. Once you understand the nature of the problem, let’s do our best to resolve it.

Fixing IO bug: Network adapter could not connect to Oracle SQL



Updated: February 2024

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Fixing IO bug: Network adapter could not connect to Oracle SQL

Make sure your records are correct

To eliminate the “Network adapter failed to connect” error, first, check that you entered your username and password correctly, as well as the correct hostname and port number. These are little things, but they can’t be avoided. After all, “it’s the little things in a relationship that matters most.”

I posted a bctt tweet asking for “How to fix “Network adapter failed to connect” in just two steps”]

Visit the listener to find the exact hostname and port number.
Listeners are server processes and your server will have listener.ora if you have access. If not, check tnsnames.ora.

If the listener.ora has a hostname and port number entered, confirm that they are valid.

This connection name is SCPO and it is not working. I don’t know why or if that matters. Here are two screens from Oracle SQL Developer – SCPO is the connection name that isn’t working. As far as I can tell from Oracle, they are interchangeable… a screenshot from tnsnames.ora file demonstrates both connections are similarly configured.

Check the hostname and port number of your SID in the TNSnames.ora file by looking for an entry that has the same name as your SID.

You can skip the next step if you’re able to establish a network connection. If it isn’t working, follow the next step.

Is your listener on pause?

It is possible that the headset isn’t receiving audio and that is causing the error message. If this is the case, simply open a command prompt with admin privileges and type:

Status: C:/lsnrctl

A listener’s status can be found by running this command.
As shown in the figure below, an down listener clearly indicates an issue with your server.

It was unable to establish a connection with the Network Adapter due to an Io exception

The listener starts with the following code.

Lsnrctl start C:/.

The listener will benefit from this because it will provide speed.



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Frequently Asked Questions

SQLException: except that the network adapter failed to establish a connection. This can happen if the connection URL/string is incorrect. The listening (maintenance) process is not running.

  1. Go to the menu where you can select SQL Developer :
  2. Select Oracle - ORACLE_HOME.
  3. Select application development.
  4. Select SQL Developer.
  5. In the navigation frame of the window, click the Connections button.
  6. In the Connections pane, click the New Connection icon.

  1. Run Oracle SQL Developer locally. The Oracle SQL Developer home page appears.
  2. In the Connections section, right-click Connections.
  3. Select New Connection.
  4. In the Select New/Database Connections dialog box, make the following entries:
  5. Click Test.
  6. Select Connect.
  7. Open the new connection.

To resolve the "Network adapter could not connect" error, first make sure that you enter the correct user name and password, as well as the correct hostname and port number. Make sure that the host and port entry in the listening radio box is a valid hostname and port number.

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Mark Ginter is a tech blogger with a passion for all things gadgets and gizmos. A self-proclaimed "geek", Mark has been blogging about technology for over 15 years. His blog, techquack.com, covers a wide range of topics including new product releases, industry news, and tips and tricks for getting the most out of your devices. If you're looking for someone who can keep you up-to-date with all the latest tech news and developments, then be sure to follow him over at Microsoft.