How can I figure out why cURL is hanging and unresponsive?

I am trying to track down an issue with a cURL call in PHP. It works fine in our test environment, but not in our production environment. When I try to execute the cURL function, it just hangs and never ever responds. I have tried making a cURL connection from the command line and the same thing happens.

I'm wondering if cURL logs what is happening somewhere, because I can't figure out what is happening during the time the command is churning and churning. Does anyone know if there is a log that tracks what is happening there?

I think it is connectivity issues, but our IT guy insists I should be able to access it without a problem. Any ideas? I'm running CentOS and PHP 5.1.

Updates: Using verbose mode, I've gotten an error 28 "Connect() Timed Out". I tried extending the timeout to 100 seconds, and limiting the max-redirs to 5, no change. I tried pinging the box, and also got a timeout. So I'm going to present this back to IT and see if they will look at it again. Thanks for all the help, hopefully I'll be back in a half-hour with news that it was their problem.

Update 2: Turns out my box was resolving the server name with the external IP address. When IT gave me the internal IP address and I replaced it in the cURL call, everything worked great. Thanks for all the help everybody.

Solution

In your php, you can set the CURLOPT_VERBOSE variable:

curl_setopt($curl, CURLOPT_VERBOSE, TRUE);

This then logs to STDERR, or to the file specified using CURLOPT_STDERR (which takes a file pointer):

curl_setopt($curl, CURLOPT_STDERR, $fp);

From the command line, you can use the following switches:

--verbose to report more info to the command line
--trace <file> or --trace-ascii <file> to trace to a file

You can use --trace-time to prepend time stamps to verbose/file outputs