What is utl_tcp and utl_smtp tx_timeout parameter do ?

Question

Hi All,
I tried the following in DBServerA (10.10.10.10 - for example) :
test_conn := utl_tcp.open_connection (remote_host => '10.2.90.100'
,remote_port => 25
,tx_timeout => 10 );
l_mail_conn := UTL_SMTP.OPEN_CONNECTION(host => '10.2.90.100'
,port => 25
,tx_timeout => 10);
now, in DBServerA, the smtp host 10.2.90.100 can be ping'd - however doing a telnet (e.g. telnet 10.2.90.100 25) will fail - because port 25 is blocked by the firewall for the smtp host.
Using UTL_TCP I get the following error in around 3 to 4 minutes:
"ORA-29260: network error: TNS:operation timed out"
Using UTL_SMTP I get the following error in around 3 to 4 minutes:
"ORA-29278: SMTP transient error: 421 Service not available"
My question now is although I set the tx_timeout parameter for both procedures with a 10 seconds value - why is that I only get the error message at around 3 to 4 minutes?
What I really want to achieve is - how can I get immediate feedback if my PL/SQL program can connect to 10.2.90.100 at port 25 ?
Is there a way? - I would just like to control the connection timeout timing precisely - and not relay on external settings (e.g. O/S)
The reason for the above requirement is to implement a "Primary SMTP Service" and a "Secondary SMTP Service" - essentially if the Primary SMTP Host IP Address fails to connect, then the PL/SQL code should try to connect to the "Secondary SMTP Host IP Address".
One thing to note is that during this 3 to 4 minutes wait time - the Oracle Connection is held up - if this now happens to the many application calls to the PL/SQL procedure - then potentially there can be a problem in many Oracle Connections opening up. - so a PL/SQL solution that would provide an immediate feedback if the SMTP service is accessible or not is ideal.
I'm using Oracle 10gR1 @ Solaris
The following command below will give me 3 minutes (agreed upon to not change this setting as it will affect all other programs/services)
"/usr/sbin/ndd -get /dev/tcp tcp_ip_abort_cinterval"
The following command below will give me 1 minute (agreed upon to not change this setting as it will affect all other programs/services)
"/usr/sbin/ndd -set /dev/tcp tcp_time_wait_interval"
Please help!
Many Thanks,
Henry

Answer 1

Hi,
Anyone? I saw many articles in Metalink regarding the tx_timeout parameter - also one which a customer is demanding an explanation and enhancement on the tx_timeout parameter. Come to think of it, when will it work? only for Exchange? (found some hints on this in metalink).
But still, is there no other way to immediately know if the port has opened or not?
I will try the following: http://www.oraclenerd.com/2008/11/javaplsql-port-scanner-ii.html , but still would prefer a PL/SQL solution though.
Many Thanks,
Henry Wu