IO Error: The Network Adapter could not establish the connection during DS creation in weblogic

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Applies to:
Weblogic: 10.3.6
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Problem Summary:
Unable to configure a datasource becuase of IO Error: The Network Adapter could not establish the connection.

Error:
IO Error: The Network Adapter could not establish the connection<br/>oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:465)<br/>oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:546)<br/>oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:232)<br/>oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)<br/>oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:521)<br/>oracle.jdbc.pool.OracleDataSource.getPhysicalConnection(OracleDataSource.java:280)<br/>oracle.jdbc.xa.client.OracleXADataSource.getPooledConnection(OracleXADataSource.java:469)<br/>oracle.jdbc.xa.client.OracleXADataSource.getXAConnection(OracleXADataSource.java:156)<br/>oracle.jdbc.xa.client.OracleXADataSource.getXAConnection(OracleXADataSource.java:101)<br/>weblogic.jdbc.common.internal.DataSourceUtil.testConnection0(DataSourceUtil.java:356)<br/>weblogic.jdbc.common.internal.DataSourceUtil.access$000(DataSourceUtil.java:22)<br/>weblogic.jdbc.common.internal.DataSourceUtil$1.run(DataSourceUtil.java:254)<br/>java.security.AccessController.doPrivileged(Native Method)<br/>weblogic.jdbc.common.internal.DataSourceUtil.testConnection(DataSourceUtil.java:251)<br/>com.bea.console.utils.jdbc.JDBCUtils.testConnection(JDBCUtils.java:751)<br/>com.bea.console.actions.jdbc.datasources.createjdbcdatasource.CreateJDBCDataSource.testConnectionConfiguration(CreateJDBCDataSource.java:474)<br/>sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)<br/>sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)<br/>sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)<br/>java.lang.reflect.Method.invoke(Method.java:606)<br/>..

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Root Cause:
Either wrong TNS details are used in JDBC URL of Data source or unable to connect to the DB server host because of firewall.

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Resolution:
1. Make sure TNS entries used are valid for host, port and SID/Service name. Can confirm with DBA.
2. Use telnet to make sure DB is listening on the given PORT
    telnet DBHostName port
    e.g. telnet localhost 1521
3. Use dbping utility  to test DB network connectivity from weblogic host.
    java -classpath /OraclePS6/Middleware/wlserver_10.3/server/lib/weblogic.jar utils.dbping
ORACLE_THIN dbusername dbpassword dbURL
    e.g.
    java -classpath /OraclePS6/Middleware/wlserver_10.3/server/lib/weblogic.jar utils.dbping ORACLE_THIN soademo soademo localhost:1521/xe