const int TIMEOUT = 10; // seconds
#endregion Fields
#region Methods
/// <summary>
/// Updates the isURLmissing parameter.
/// If the URL returns 404 or the connection is broken, it's missing. Else, we suppose it's fine.
/// This should or can be used along with web async instance's isURLcheckingCompleted parameter
/// inside a IEnumerator method capable of yield return for it, although it's mostly for clarity.
/// Here's an usage example:
///
/// WebAsync webAsync = new WebAsync(); StartCoroutine( webAsync.CheckForMissingURL(url) );
/// while (! webAsync.isURLcheckingCompleted) yield return null;
/// bool result = webAsync.isURLmissing;
///
/// </summary>
/// <param name='url'>
/// A fully formated URL.
/// </param>
public IEnumerator CheckForMissingURL(string url)
{
isURLcheckingCompleted = false;
isURLmissing = false;
Uri httpSite = new Uri(url);
WebRequest webRequest = WebRequest.Create(httpSite);
// We need no more than HTTP's head
webRequest.Method = "HEAD";
// Get the request's reponse
requestState = null;
// Manually iterate IEnumerator, because Unity can't do it (and this does not inherit StartCoroutine from MonoBehaviour)
IEnumerator e = GetResponse(webRequest);
while (e.MoveNext()) yield return e.Current;
while (!isResponseCompleted) yield return null; // this while is just to be sure and clear
// Deal up with the results
if (requestState.errorMessage != null) {
if (requestState.errorMessage.Contains("404") || requestState.errorMessage.Contains("NameResolutionFailure")) {
isURLmissing = true;
} else {
Debug.LogError("[WebAsync] Error trying to verify if URL '" + url + "' exists: " + requestState.errorMessage);
}
}
isURLcheckingCompleted = true;
}
/// <summary>
/// Equivalent of webRequest.GetResponse, but using our own RequestState.
/// This can or should be used along with web async instance's isResponseCompleted parameter
/// inside a IEnumerator method capable of yield return for it, although it's mostly for clarity.
/// Here's an usage example:
///
/// WebAsync webAsync = new WebAsync(); StartCoroutine( webAsync.GetReseponse(webRequest) );
/// while (! webAsync.isResponseCompleted) yield return null;
/// RequestState result = webAsync.requestState;
///
/// </summary>
/// <param name='webRequest'>
/// A System.Net.WebRequest instanced var.
/// </param>
public IEnumerator GetResponse(WebRequest webRequest)
{
isResponseCompleted = false;
requestState = new RequestState();
// Put the request into the state object so it can be passed around
requestState.webRequest = webRequest;
// Do the actual async call here
IAsyncResult asyncResult = (IAsyncResult)webRequest.BeginGetResponse(
new AsyncCallback(RespCallback), requestState);
// WebRequest timeout won't work in async calls, so we need this instead
ThreadPool.RegisterWaitForSingleObject(
asyncResult.AsyncWaitHandle,
new WaitOrTimerCallback(ScanTimeoutCallback),
requestState,
(TIMEOUT * 1000), // obviously because this is in miliseconds
true
);
// Wait until the the call is completed
while (!asyncResult.IsCompleted) { yield return null; }
// Help debugging possibly unpredictable results
if (requestState != null) {
if (requestState.errorMessage != null) {
// this is not an ERROR because there are at least 2 error messages that are expected: 404 and NameResolutionFailure - as can be seen on CheckForMissingURL
Debug.Log("[WebAsync] Error message while getting response from request '" + webRequest.RequestUri.ToString() + "': " + requestState.errorMessage);
}
}
isResponseCompleted = true;
}
