C Connecting Through Proxy

Question

I work in a office which requires all connections to be made through a specific http proxy  I need to write a simple application to query some values from a webserver - it s easy if there were no proxy  How can I make the C  application proxy-aware  How can I make any sort of connection through a proxy

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var getHtmlWeb   new HtmlWeb     AutoDetectEncoding   false  OverrideEncoding   Encoding GetEncoding  iso-8859-2                   WebProxy myproxy   new WebProxy  127 0 0 1 8888   false               NetworkCredential cred    NetworkCredential CredentialCache DefaultCredentials              var document   getHtmlWeb Load  URL    GET   myproxy  cred

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If you are using WebClient  it has a Proxy property you can use   As other have mentioned  there are several ways to automate proxy setting detection usage  Web Config    lt system net gt      lt defaultProxy enabled  true  useDefaultCredentials  true  gt        lt proxy usesystemdefault  true  bypassonlocal  true    gt      lt  defaultProxy gt   lt  system net gt    Use of the WebProxy class as described in this article     You can also cofigure the proxy settings directly  config or code  and your app will then use those   Web Config    lt system net gt     lt defaultProxy gt       lt proxy       proxyaddress  http    proxy address   proxy port         bypassonlocal  false        gt     lt  defaultProxy gt   lt  system net gt    Code   HttpWebRequest request    HttpWebRequest WebRequest Create  url    WebProxy myproxy   new WebProxy   proxy address   proxy port    false   request Proxy   myproxy  request Method    GET   HttpWebResponse response    HttpWebResponse  request GetResponse

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This code has worked for me   WebClient wc   new WebClient    wc Proxy Credentials   CredentialCache DefaultCredentials

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I am going to use an example to add to the answers above   I ran into proxy issues while trying to install packages via Web Platform Installer  That too uses a config file which is WebPlatformInstaller exe config  I tried the edits suggest in this IIS forum which is    lt  xml version  1 0  encoding  utf-8    gt   lt configuration gt       lt system net gt            lt defaultProxy enabled  True  useDefaultCredentials  True   gt            lt  system net gt   lt  configuration gt    and   lt  xml version  1 0  encoding  utf-8    gt   lt configuration gt        lt system net gt            lt defaultProxy gt                   lt proxy                 proxyaddress  http   yourproxy company com 80                  usesystemdefault  True                 autoDetect  False    gt            lt  defaultProxy gt        lt  system net gt   lt  configuration gt    None of these worked   What worked for me was this -    lt system net gt           lt defaultProxy enabled  true  useDefaultCredentials  false  gt         lt module type  WebPI Net AuthenticatedProxy  WebPI Net  Version 1 0 0 0  Culture neutral  PublicKeyToken 79a8d77199cbf3bc    gt       lt  defaultProxy gt      lt  system net gt    The module needed to be registered with Web Platform Installer in order to use it

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Try this code  Call it before making any http requests  The code will use the proxy from your Internet Explorer Settings - one thing though  I use proxy Credentials        because my proxy server is an NTLM authenticated Internet Acceleration Server  Give it a whizz   static void setProxy         WebProxy proxy    WebProxy WebProxy GetDefaultProxy        if proxy Address    null                proxy Credentials   System Net CredentialCache DefaultNetworkCredentials          WebRequest DefaultWebProxy   new System Net WebProxy proxy Address  proxy BypassProxyOnLocal  proxy BypassList  proxy Credentials

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Automatic proxy detection is a process by which a Web proxy server is identified by the system and used to send requests on behalf of the client  This feature is also known as  Web Proxy Auto-Discovery  WPAD   When automatic proxy detection is enabled  the system  attempts to locate a proxy configuration script that is responsible for returning the set of proxies that can be used for the request   http   msdn microsoft com en-us library fze2ytx2 aspx

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This is easily achieved either programmatically  in your code  or declaratively in either the web config or the app config   You can programmatically create a proxy like so   HttpWebRequest request    HttpWebRequest WebRequest Create   ultimate destination of your request     WebProxy myproxy   new WebProxy   your proxy address     your proxy port number    myproxy BypassProxyOnLocal   false  request Proxy   myproxy  request Method    GET   HttpWebResponse response    HttpWebResponse  request GetResponse      You re basically assigning the WebProxy object to the request object s proxy property   This request will then use the proxy you define   To achieve the same thing declaratively  you can do the following    lt system net gt     lt defaultProxy gt       lt proxy       proxyaddress  http    your proxy address and port number         bypassonlocal  false        gt     lt  defaultProxy gt   lt  system net gt    within your web config or app config    This sets a default proxy that all http requests will use   Depending upon exactly what you need to achieve  you may or may not require some of the additional attributes of the defaultProxy   proxy element  so please refer to the documentation for those

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If you want the app to use the system default proxy  add this to your Application exe config  where application exe is the name of your application     lt system net gt      lt defaultProxy enabled  true  useDefaultCredentials  true  gt      lt proxy usesystemdefault  true  bypassonlocal  true    gt      lt  defaultProxy gt   lt  system net gt    More details can be found on in the MSDN article on System Net

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Foole s code worked perfectly for me  but in  NET 4 0  don t forget to check if Proxy is NULL  which means no proxy configured  outside corporate environment   So here s the code that solved my problem with our corporate proxy  WebClient web   new WebClient    if  web Proxy    null      web Proxy Credentials   System Net CredentialCache DefaultNetworkCredentials

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This one-liner works for me   WebRequest DefaultWebProxy Credentials   CredentialCache DefaultNetworkCredentials    CredentialCache DefaultNetWorkCredentials is the proxy settings set in Internet Explorer   WebRequest DefaultWebProxy Credentials is used for all internet connectivity in the application

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