ServicePoint 类

地址：https://docs.microsoft.com/zh-cn/dotnet/api/system.net.servicepoint?view=netframework-4.7.2

提供 HTTP 连接的连接管理。

下面的代码示例创建一个ServicePoint连接到 URI www.contoso.com的对象。

// This example shows how to use the ServicePoint and ServicePointManager classes.
// The ServicePointManager class uses the ServicePoint class to manage connections
// to a remote host. The networking classes reuse service points for all
// requests to a given URI. In fact, the same ServicePoint object
// is used to issue requests to Internet resources identified by the same
// scheme identifier (for example,  HTTP) and host fragment (for example,  www.contoso.com).
// This should improve your application performance.
// Reusing service points in this way can help improve application performance.
using System;
using System.Net;
using System.Threading;
using System.Text.RegularExpressions;

namespace Mssc.Services.ConnectionManagement
{
    class TestServicePoint
    {
        private static void ShowProperties(ServicePoint sp)
        {
            Console.WriteLine("Done calling FindServicePoint()...");

            // Display the ServicePoint Internet resource address.
            Console.WriteLine("Address = {0} ", sp.Address.ToString());

            // Display the date and time that the ServicePoint was last
            // connected to a host.
            Console.WriteLine("IdleSince = " + sp.IdleSince.ToString());

            // Display the maximum length of time that the ServicePoint instance
            // is allowed to maintain an idle connection to an Internet
            // resource before it is recycled for use in another connection.
            Console.WriteLine("MaxIdleTime = " + sp.MaxIdleTime);

            Console.WriteLine("ConnectionName = " + sp.ConnectionName);

            // Display the maximum number of connections allowed on this
            // ServicePoint instance.
            Console.WriteLine("ConnectionLimit = " + sp.ConnectionLimit);

            // Display the number of connections associated with this
            // ServicePoint instance.
            Console.WriteLine("CurrentConnections = " + sp.CurrentConnections);

            if (sp.Certificate == null)
                Console.WriteLine("Certificate = (null)");
            else
                Console.WriteLine("Certificate = " + sp.Certificate.ToString());

            if (sp.ClientCertificate == null)
                Console.WriteLine("ClientCertificate = (null)");
            else
                Console. WriteLine("ClientCertificate = " + sp.ClientCertificate.ToString());

            Console.WriteLine("ProtocolVersion = " + sp.ProtocolVersion.ToString());
            Console.WriteLine("SupportsPipelining = " + sp.SupportsPipelining);

            Console.WriteLine("UseNagleAlgorithm = " + sp.UseNagleAlgorithm.ToString());
            Console.WriteLine("Expect 100-continue = " + sp.Expect100Continue.ToString());
        }

        private static void makeWebRequest(int hashCode, string Uri)
        {
            HttpWebResponse res = null;

            // Make sure that the idle time has elapsed, so that a new
            // ServicePoint instance is created.
            Console.WriteLine("Sleeping for 2 sec.");
            Thread.Sleep(2000);
            try
            {
                // Create a request to the passed URI.
                HttpWebRequest req = (HttpWebRequest)WebRequest.Create(Uri);

                Console.WriteLine("\nConnecting to " + Uri + " ............");

                // Get the response object.
                res = (HttpWebResponse)req.GetResponse();
                Console.WriteLine("Connected.\n");

                ServicePoint currentServicePoint = req.ServicePoint;

                // Display new service point properties.
                int currentHashCode = currentServicePoint.GetHashCode();

                Console.WriteLine("New service point hashcode: " + currentHashCode);
                Console.WriteLine("New service point max idle time: " + currentServicePoint.MaxIdleTime);
                Console.WriteLine("New service point is idle since " + currentServicePoint.IdleSince );

                // Check that a new ServicePoint instance has been created.
                if (hashCode == currentHashCode)
                    Console.WriteLine("Service point reused.");
                else
                    Console.WriteLine("A new service point created.") ;
            }
            catch (Exception e)
            {
                Console.WriteLine("Source : " + e.Source);
                Console.WriteLine("Message : " + e.Message);
            }
            finally
            {
                if (res != null)
                    res.Close();
            }
        }

        // Show the user how to use this program when wrong inputs are entered.
        private static void showUsage()
        {
            Console.WriteLine("Enter the proxy name as follows:");
            Console.WriteLine("\tcs_servicepoint proxyName");
        }

        public static void Main(string[] args)
        {
            int port = 80;

            // Define a regular expression to parse the user's input.
            // This is a security check. It allows only
            // alphanumeric input strings between 2 to 40 characters long.
            Regex rex = new Regex(@"^[a-zA-Z]\w{1,39}$");

            if (args.Length < 1)
            {
                showUsage();
                return;
            }
            string proxy = args[0];

            if ((rex.Match(proxy)).Success != true)
            {
                Console.WriteLine("Input string format not allowed.");
                return;
            }
            string proxyAdd = "http://" + proxy + ":" + port;

            // Create a proxy object.  
            WebProxy DefaultProxy = new WebProxy(proxyAdd, true);

            // Set the proxy that all HttpWebRequest instances use.
            WebRequest.DefaultWebProxy = DefaultProxy;

            // Get the base interface for proxy access for the
            // WebRequest-based classes.
            IWebProxy Iproxy = WebRequest.DefaultWebProxy;

            // Set the maximum number of ServicePoint instances to
            // maintain. If a ServicePoint instance for that host already
            // exists when your application requests a connection to
            // an Internet resource, the ServicePointManager object
            // returns this existing ServicePoint instance. If none exists
            // for that host, it creates a new ServicePoint instance.
            ServicePointManager.MaxServicePoints = 4;

            // Set the maximum idle time of a ServicePoint instance to 10 seconds.
            // After the idle time expires, the ServicePoint object is eligible for
            // garbage collection and cannot be used by the ServicePointManager object.
            ServicePointManager.MaxServicePointIdleTime = 10000;

            ServicePointManager.UseNagleAlgorithm = true;
            ServicePointManager.Expect100Continue = true;
            ServicePointManager.CheckCertificateRevocationList = true;
            ServicePointManager.DefaultConnectionLimit = ServicePointManager.DefaultPersistentConnectionLimit;
            // Create the Uri object for the resource you want to access.
            Uri MS = new Uri("http://msdn.microsoft.com/");

            // Use the FindServicePoint method to find an existing
            // ServicePoint object or to create a new one.  
            ServicePoint servicePoint = ServicePointManager.FindServicePoint(MS, Iproxy);

            ShowProperties(servicePoint);

            int hashCode = servicePoint.GetHashCode();

            Console.WriteLine("Service point hashcode: " + hashCode);

            // Make a request with the same scheme identifier and host fragment
            // used to create the previous ServicePoint object.
            makeWebRequest(hashCode, "http://msdn.microsoft.com/library/");
        }
    }
}

注解

ServicePoint类根据传递给资源的统一资源标识符 (URI) 中的主机信息来处理与 Internet 资源的连接。

与资源的初始连接将确定ServicePoint对象维护的信息, 该信息随后由对该资源的所有后续请求共享。

ServicePoint对象由ServicePointManager类管理, 并根据需要ServicePointManager.FindServicePoint由方法创建。

ServicePoint永远不会直接创建对象, 而是始终由ServicePointManager类创建和管理对象。

可创建的最ServicePoint大对象数ServicePointManager.MaxServicePoints由属性设置。

每ServicePoint个对象都保持与 Internet 资源的连接, 直到它的空闲时间超过MaxIdleTime在属性中指定的时间。

ServicePoint 当MaxIdleTime超出该值时, 可以将其回收到其他连接。

的默认值MaxIdleTime ServicePointManager.MaxServicePointIdleTime由属性设置。

如果将ServicePoint属性设置为-1 以外的值, 并且在指定的时间过后, 则在服务下一个请求后将关闭活动连接。

ConnectionLeaseTimeout 这对于不需要无限期打开的活动连接的应用程序非常有用, 因为这些应用程序默认为。

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demo没有调通，proxy 找不到一个合适的值；

………………

暂时未解决。