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Error occurs on a .NET client that consumes a Web service through an HTTP proxy server

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This article helps you resolve a problem where an error (The underlying connection was closed: The remote name could not be resolved) occurs when you use a .NET client to consume a Web service through an HTTP proxy server.

Original product version:   .NET Framework
Original KB number:   318140

Symptoms

When you use a .NET client to consume a Web service through an HTTP proxy server, you may receive the following error message:

The underlying connection was closed: The remote name could not be resolved.

Cause

An HTTP proxy server exists between the Web service and the .NET client, and the proper proxy settings have not been configured.

Resolution

To resolve this problem, supply the proper proxy configuration settings to the .NET client.

The following are the default settings in the Machine.config file:

<configuration>
    <system.net>
        <defaultProxy>
            <proxy
               usesystemdefault = "true"
            />
        </defaultProxy>
    </system.net>
</configuration>

If the default settings do not automatically detect the proxy server settings, set usessystemdefault to false, and then explicitly designate the proxy server. To designate the proxy server explicitly, use either the Machine.config or Web.config file, or specify the server programmatically.

To specify the proxy server, set the Machine.config or Web.config file settings as follows:

<configuration>
    <system.net>
        <defaultProxy>
            <proxy
               usesystemdefault = "false"
               proxyaddress="http://proxyserver"
               bypassonlocal="true"
            />
        </defaultProxy>
    </system.net>
</configuration>

To change the settings programmatically by using a WebProxy object, use the following sample code:

using System.Net;
com.someserver.somewebservice.someclass MyWebServiceClass = new com.someserver.somewebservice.someclass ();
IWebProxy proxyObject = new WebProxy ("http://myproxyserver:80", true);
MyWebServiceClass.Proxy = proxyObject;
MyWebServiceClass.MyWebMethod ();

Proxy servers that require NTLM authentication

To set Windows NT LAN Manager (NTLM) authentication for the proxy server, use the following sample code:

using System.Net;
WebProxy myProxy = new WebProxy ("http://proxyserver:port", true);
myProxy.Credentials = CredentialCache.DefaultCredentials;
FindServiceSoap myFindService = new FindServiceSoap ();
myFindService.Proxy = myProxy;

You can also use system-wide proxy as default. To do this, use the following settings in the configuration file:

<configuration>
    <system.net>
        <defaultProxy>
            <proxy
               proxyaddress = "http://proxyserver:80"
               bypassonlocal = "true"
            />
        </defaultProxy>
    </system.net>
</configuration>

References