// MAIN METHOD
public void GetTags (string applicationCode, string HWID, Action <string> callback)
{
    const string applicationProperty = "application";
    const string hwidProperty = "hwid";
    JObject json = new JObject (new JProperty (applicationProperty, applicationCode), new JProperty (hwidProperty, HWID));

    const string getTagsAction = "getTags";
    CallUri (getTagsAction, json, callback);
}

private void CallUri (string action, JObject data, Action <string> callback)
{
    string uriString = string.Format ("https://cp.pushwoosh.com/json/1.3/{0}", action);
    Uri url = new Uri (uriString);

    const string requestProperty = "request";
    JObject json = new JObject (new JProperty (requestProperty, data));

    DoPostRequest (url, json, callback);
}

private void DoPostRequest (Uri url, JObject data, Action <string> callback)
{
    HttpWebRequest req = (HttpWebRequest) HttpWebRequest.Create (url);
    req.ContentType = "text/json";
    req.Method = "POST";

    using (var streamWriter = new StreamWriter (req.GetRequestStream ())) {
        streamWriter.Write (data.ToString ());
    }

    HttpWebResponse httpResponse;

    try {
        httpResponse = (HttpWebResponse) req.GetResponse ();
    }
    catch (Exception exc) {
        throw new Exception (string.Format ("Problem with {0}, {1}", url, exc.Message));
    }

    using (var streamReader = new StreamReader (httpResponse.GetResponseStream ())) {
        var responseText = streamReader.ReadToEnd ();

        callback (responseText);

        Debug.LogFormat ("responseText: {0}", responseText);
    }
}