How can I programmatically remove the 2 connection

问题:

Those \"fine\" RFCs mandate from every RFC-client that they beware of not using more than 2 connections per host...

Microsoft implemented this in WebClient. I know that it can be turned off with

App.config:

<?xml version=\"1.0\" encoding=\"utf-8\" ?> 
<configuration> 
 <system.net> 
  <connectionManagement> 
   <add address=\"*\" maxconnection=\"100\" /> 
  </connectionManagement> 
 </system.net> 
</configuration> 

(found on http://social.msdn.microsoft.com/forums/en-US/netfxnetcom/thread/1f863f20-09f9-49a5-8eee-17a89b591007 )

But how can I do it programmatically?

Accordin to http://msdn.microsoft.com/en-us/library/system.net.servicepointmanager.defaultconnectionlimit.aspx

\"Changing the DefaultConnectionLimit property has no effect on existing ServicePoint objects; it affects only ServicePoint objects that are initialized after the change. If the value of this property has not been set either directly or through configuration, the value defaults to the constant DefaultPersistentConnectionLimit.\"

I\'d like best to configure the limit when I instanciate the WebClient, but just removing this sad limitation programmatically at the start of my programm would be fine, too.

The server I access is not a regular webserver in the internet, but under my control and in the local lan. I want to do API-calls, but I don\'t use webservices or remoting

回答1:

With some tips from here and elsewhere I managed to fix this in my application by overriding the WebClient class I was using:

class AwesomeWebClient : WebClient {
    protected override WebRequest GetWebRequest(Uri address) {
        HttpWebRequest req = (HttpWebRequest)base.GetWebRequest(address);
        req.ServicePoint.ConnectionLimit = 10;
        return (WebRequest)req;
    }
}

回答2:

for those interested:

System.Net.ServicePointManager.DefaultConnectionLimit = x (where x is your desired number of connections)

no need for extra references

just make sure this is called BEFORE the service point is created as mentioned above in the post.

回答3:

This solution allows you to change the connection limit at any time:

private static void ConfigureServicePoint(Uri uri)
{
    var servicePoint = ServicePointManager.FindServicePoint(uri);

    // Increase the number of TCP connections from the default (2)
    servicePoint.ConnectionLimit = 40;
}

The 1st time anyone calls this FindServicePoint, a ServicePoint instance is created and a WeakReference is created to hold on to it inside the ServicePointManager. Subsequent requests to the manager for the same Uri return the same instance. If the connection isn\'t used after, the GC cleans it up.

回答4:

If you find the ServicePoint object being used by your WebClient, you can change its connection limit. HttpWebRequest objects have an accessor to retrieve the one they were constructed to use, so you could do it that way. If you\'re lucky, all your requests might end up sharing the same ServicePoint so you\'d only have to do it once.

I don\'t know of any global way to change the limit. If you altered the DefaultConnectionLimit early enough in execution, you\'d probably be fine.

Alternately, you could just live with the connection limit, since most server software is going to throttle you anyway. :)

回答5:

We have a situation regarding the above piece of configuration in App.Config

In order for this to be valid in a CONSOLE Application, we added the System.Configuration reference dll. Without the reference, the above was useless.