Oracle client connection through VPN

If you are attempting to connect to your Oracle RDS or EC2-based Oracle DB through SQL Developer and SQL Plus from a client machine, you will get a ORA-12541: TNS:no listener if connecting through VPN ( or maybe a corporate firewall ). If you can connect to your instance through SQL Plus on an EC2 instance, it could be because of VPN or a firewall.

Oracle RDS on AWS - Connecting with DB tools

After taking some time to make sure security groups for my Oracle RDS instances were set properly, I was able to connect to two Oracle RDS instances I have spun up.  A few comments on the various tools:
1. SQL Plus - You can use the instant client latest 11g release.  You do need to make sure the connect string is set properly.  How to do this can be found here:
http://docs.amazonwebservices.com/AmazonRDS/2012-01-15/UserGuide/USER_ConnectToOracleInstance.html
2. SQL Developer - I used the 64 bit version that does not have the JDK installed so you will need to download the JDK separately,
3. TOAD - You need to point TOAD to the Oracle client software. This is done by adding Oracle client to the system path.  I have another blog entry on this.

Connecting to an EC2 based Oracle instance works the same way.