We have installed Oracle 10g on Windows-XP machine. But when a client (another pc – windows 2003) is trying to connect to the database, then the following error is being generated “ORA-12170: TNS: Connect timeout occurred”
We ensure that the tnsnames.ora file has the correct information i.e. hostname, port, and sid. When we tnsping the sid, it gives “TNS-12535: TNS: operation timed out” error.
So, we had to resolve this problem by turning OFF the Firewall on Server Side (Windows –XP). After that we could successfully connect to the database, and able to tnsping sid as well.
Conclusion: If you are facing these problems due to other reasons, I would request you to take a look at oracle metalink notes for the same.