Re: JDBCR4 - Driver_ConnProp

Aaaahhhh.... Thanks Scott, as always, clear and precise explaination.

One question... Do you think it would be ok to use alarm/signal() to
timeout this operation?

thanks

"Scott Klement" <rpg400-l@xxxxxxxxxxxxxxxx> wrote in message
news:<mailman.807.1251997245.1811.rpg400-l@xxxxxxxxxxxx>...

In our world of computer vandals, attackers, denial-of-service

attacks,

spam, malware and the like, many companies choose to block ICMP
messages. Or simply discard unwanted connection requests from a

firewall.

The ICMP protocol is the "error message" protocol of the Internet.

When

you do something wrong (such as try to connect to a JDBC server on a
computer that doesn't have one running) the TCP/IP stack is supposed

to

send an ICMP message saying "connection refused". That tells you that

the computer isn't accepting connections on the given port.

But people block that message. Or prevent it entirely by configuring

a

firewall to simply discard the connection request so the computer

never

even receives the request (and therefore can't tell you that it

failed)

The result is that your program sits and waits for a response to the
request. It sits and sits and sits and waits until a response is
received. If there is no response coming, it will sit indefinitely.

Normally, TCP/IP software has the option to set a "timeout" value to
limit how long it sits and waits. I don't know if Oracle has that
option in their JDBC driver (I don't use Oracle) or if they do have

such

an option, I don't know what the default value is.

But assuming that the value is either very long, or set to "wait
indefinitely" by default, then it would make perfect sense that using
the wrong IP address would certainly cause the problem you describe.

Incidentally -- coding an IP address instead of a domain name is a
really bad idea. Please consider changing that.


Lim Hock-Chai wrote:

Ok. It appears to cause by wrong ip being put into the url. Which
makes me wonder why it stucks when wrong ip is provided.