Tomcat Problem?

I am having an unusual problem :

Using code taken from the test_http_post.php program I am able to post to test pages on a number of servers at port 80, but not to the actual target application, running on a Tomcat - port 8080.

Specifying port 8080 in the arguments and/or in the url itself seems to make no difference. According to the sysadmins, there are no blocks or restrictions or proxies on receiving side.

Any ideas?

Thanks in advance