Dear All,

I have a problem with sending http requests. I have a network. This network has a server that is visible to outside of the network and there are some other computers that are not visible and just server can see them (I call them clients). (I didn't configure this network). Now I have redhat 9.0 and apache on all of this computers. I'm sending http requests from server to client via libcurl in php code. But I didn't receive any response. I guess that the problem is from linux configurations but I'm not sure.

Please help me,

I presume you mean client to server.

Yes, you are right, there can be a lot of problems. As you didn't tell us what you already have tried, here a short non exhaustive list of things you might want to check:

Can the client ping the server?
Is there a firewall in place which might block the request?
Have you tried another client (e.g a web browser) to do the request?

Only if you have established that the connection works, you might want to play with the options of curl.

No, I mean from server to client. My server is responsing the http request and for doing its jobs distribute them between some other computers. But I didn't receive response from clients (some other computers).

I have a subnetwork. This subnetwork has a server that is the interface of the world and the subnetwork. I send http request via curl extension of the php to the computers that are in my subnetwork but they didn't response. I can ping computers in subnetwork by server and I can ping server by computers in subnetwork too.

If I understand you correctly, the setup is follows:

One server is visible to the internet (= exposed server).

If a client from the internet connects to this server, the server in turn connects to other servers (also running apache) in your local network.

And your problem is, that a www connection from the (exposed) server to the (other) servers does not work.


Even if you can ping the other server, a firewall may block (www) connections from one computer to another.

Perform the following test:

On the exposed host use telnet to connect to that server on port 80 (www).
If the connection is refused immediately, a firewall is most likely blocking that connection. The other possibility is that the web server on the other computer is not running, or not running on port 80.

In case a connection is established enter

Then press Enter two times.

This requests the root page from this web server. If you get some kind of response, then that web server is running.


You may repeat the telnet command on the other computer. In this case the web server and telnet command run on the same computer (with no firewall blocking them). If this does not work as well, you should examine the web server on that computer.

Thanks alot,

My problem was that I'm using the following code:

curl_setopt(<resource name>, CURLOPT_POST, 1);

without using the following code:

curl_setopt(<resource name>, CURLOPT_POSTFIELDS, <post fields>);

On linux distribution of php the above situation doesn't work but in windows it works.
By setting CURLOPT_POSTFIELDS, codes will work correctly.