Question

我正在尝试创建一个检查网站是否在线的功能，但是在超时时遇到了一些问题。我想将其限制为最多3秒，如果在3秒内没有响应我应该看到该页面处于脱机状态。

我的尝试：

class OnlineCheck
    {
        public static bool IsOnline(string url)
        {
            try
            {
                WebClient webclient = new WebClient();
                webclient.Headers.Add(HttpRequestHeader.KeepAlive, "1000");

                webclient.OpenRead(url);
            }
            catch { return false; }

            return true;
        }
    }

Answer 1

如果您想检查该网站是否在线，您对该网页的内容并不感兴趣，只需获得回复即可。为了提高效率，您应该只请求http标头。以下是一个关于如何做的快速示例：

private static IEnumerable<HttpStatusCode> onlineStatusCodes = new[]
{
    HttpStatusCode.Accepted,
    HttpStatusCode.Found,
    HttpStatusCode.OK,
    // add more codes as needed
};

private static bool IsSiteOnline(string url, int timeout)
{
    HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
    {
        if (request != null)
        {
            request.Method = "HEAD"; // get headers only
            request.Timeout = timeout;
            using (var response = request.GetResponse() as HttpWebResponse)
            {
                return response != null && onlineStatusCodes.Contains(response.StatusCode);
            }
        }
    }
    return false;
}

Answer 2

WebClient不支持超时。但是你可以使用HttpWebRequest！

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Endpoint);
request.Timeout=3000;
request.GetResponse();

Answer 3

使用HttpWebRequest而不是WebClient。 HttpWebRequest类有一个超时属性。

Answer 4

您可以尝试以下代码：

        System.Net.WebRequest r = System.Net.WebRequest.Create("http://www.google.com");
        r.Timeout = 3000;

        System.Net.WebProxy proxy = new System.Net.WebProxy("<proxy address>");
        System.Net.NetworkCredential credentials = new System.Net.NetworkCredential();

        credentials.Domain = "<domain>";
        credentials.UserName = "<login>";
        credentials.Password = "<pass>";

        proxy.Credentials = credentials;
        r.Proxy = proxy;

        try
        {
            System.Net.WebResponse rsp = r.GetResponse();
        }
        catch (Exception)
        {
            MessageBox.Show("Is not avaliable");
            return;
        }

        MessageBox.Show("Avaliable!");

Answer 5

static bool isOnline (string URL)
{
    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);
    request.Timeout = 3000;

    try
    {
        WebResponse resp = request.GetResponse();
    }
    catch (WebException e)
    {
        if (((HttpWebResponse)e.Response).StatusCode == HttpStatusCode.NotFound)
        {
            return false;
        }
    }

    return true;
}

检查站点是否在线，限制超时

5 个答案: