Fsockopen times out on isps server

I have an apache server sunning at home for test purposes and I have an account with a uk isp. When using fsockopen on my home server everything works fine, I can connect on different ports (I am using specifically 25 for testing a mail server) but when I upload my site to my ISP then I can no longer connect using fsockopen - it just times out.

I take it they have a security restriction on their side preventing me from using this feature - am I correct in thinking this or i开发者_StackOverflows there another explanation for this?

Well as far as i know a timeout means that the remote host is unreachable. There are a few reasons for "unreachable", one of them is that your ISP is blocking outgoing connections wich PHP initializes. Another reason is that the remote host is blocking your connection, and a few other.

But basicly i think the reason is that your ISP is blocking the PHP feature.

Most likely, it's a firewall in "stealth" mode. When you try opening a socket to the port 25 on he remote server, it pretends that nothing's there. It's a quite common security measure.