delay sending http data with no answer

I neet to send some commands to a video server, the final URI is something like:

http://10.10.10.10/cgi-bin/fwsysget.cgi?FwModId=0&FwCgiVer=0x0001

I have a coroutine:

//Command is the full URI

 public IEnumerator cam (string command){
 float starttime = Time.realtimeSinceStartup;
 WWW www = new WWW (command);
 
 while(!www.isDone && (Time.realtimeSinceStartup - starttime <5)){
 yield return null;
 }
 www.Dispose();
 
 UnityEngine.Debug.Log ("Finished " + command + " at " + (Time.realtimeSinceStartup - starttime).ToString("F2"));
 }

My problem is that the coroutine takes 3 seconds to return, and my command takes also 3 seconds to be received by the web server. The server doesn't send any answer. If I copy-paste the same URL in chrome, the answer is instantaneous.

Am I doing something wrong by using the WWW class? Should I use WebRequest with POST, or the wwwForm class?

Thanks