HttpWebRequest.GetResponse() times out after some time - httpwebrequest

Question

I have application that sends requests to same REST server constantly and after some time HttpWebRequest.GetResponse() starts timing out i've noticed that whenever i increase System.Net.ServicePointManager.DefaultConnectionLimit it takes it longer to start timing out again, which should mean that those requests are staying active, but as far as i know i'm closing all of them.
Here is method i'm using for my requests.
Current DefaultConnectionLimit is set to 10.
Also there is 1 request that is going on throughout most of applications lifetime.
I'm using .NET Compact framework and REST server is written using WCF (.NET 4.5)
public static string HttpRequest(string request, string method, string contentType, int timeout)
{
string result = "";
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(PodesavanjaManager.TrenutnaPodesavanja.PutanjaServisa + "/" + request);
req.Method = method;
req.ContentType = contentType;
req.Timeout = timeout;
req.KeepAlive = false;
if(method == "POST")
req.ContentLength = 0;
using(Stream stream = req.GetResponse().GetResponseStream())
{
using(StreamReader reader = new StreamReader(stream))
{
result = reader.ReadToEnd();
reader.Close();
}
stream.Close();
stream.Flush();
}
return result;
}
EDIT new version of method:
public static string HttpRequest(string request, string method, string contentType, int timeout)
{
string result = "";
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(PodesavanjaManager.TrenutnaPodesavanja.PutanjaServisa + "/" + request);
req.Method = method;
req.ContentType = contentType;
req.Timeout = timeout;
req.KeepAlive = false;
if(method == "POST")
req.ContentLength = 0;
using (HttpWebResponse resp =(HttpWebResponse) req.GetResponse())
{
using (Stream stream = resp.GetResponseStream())
{
using (StreamReader reader = new StreamReader(stream))
{
result = reader.ReadToEnd();
reader.Close();
}
}
}
GC.Collect();
return result;
}

Answer 1

I agree it does behave like the connection is still in use by a resource that has not been closed. The documentation for HttpWebResponse mentions:
You must call either the Stream.Close or the HttpWebResponse.Close method to close the response and release the connection for reuse. It is not necessary to call both Stream.Close and HttpWebResponse.Close, but doing so does not cause an error.
I was hoping for a more straightforward description like "you must either close the stream returned by GetResponseStream or call the HttpWebResponse.Close method - but if my interpretation of the documentation is correct, your code is fine.
We use HttpWebRequest in our CE applications as well, and always put the response in a using block as well - you could try this:
using(HttpWebResponse response = (HttpWebResponse)req.GetResponse())
using(Stream stream = response.GetResponseStream())
{
// ...
}
Also have you checked your code for other HttpWebRequest usages, just to be sure?