How to see the reason for "could not connect to the web server" running Rails project in Netbeans 6.7/6.8?

I have a legacy Rails project (2.4) that used to work in Netbeans. But I just tried running it and got the message

"could not connect to the web server http://localhost:3000"

How do I get a more detailed explanation from Netbeans?

I don't see an开发者_StackOverflow社区y other error information.

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Netbeans will be writing it's STDERR messages, either to a console window or a logfile.