Idhttp组件用的比较多，使用中的问题也很多。目前很多网站如百度都禁止indy组件访问。因此必须注意UserAgent和http1.1的设置。.

以下是Delphi的代码：

IdHTTP1.Request.Connection:='Keep-Alive';   
IdHTTP1.Request.UserAgent:='Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; Maxthon)';   
IdHTTP1.Request.ContentType:='application/x-www-form-urlencoded';   
IdHTTP1.Request.Referer:='http://www.xxx.com';   
IdHTTP1.Request.Accept:='image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd.ms-excel, application/msword, */*';   
IdHTTP1.Request.AcceptLanguage:='zh-cn';   
IdHTTP1.Request.AcceptEncoding:='gzip, deflate';   
IdHTTP1.Request.CacheControl:='no-cache';   
IdHTTP1.ReadTimeout:=60000;   
IdHTTP1.HTTPOptions:=IdHTTP1.HTTPOptions+[hoKeepOrigProtocol];  //关键这行   
IdHTTP1.ProtocolVersion:=pv1_1;   
sHtml:=IdHTTP1.Post('http://www.xxx.com/login.asp',sPost); 

以下c++builder 采用 dHTTP1+TIdCookieManager组件登录代码:
过程大体如下：  
Cookie   =   new   TIdCookieManager(this);  
Cookie->OnNewCookie   =   &CookieNewCookie;  
IOSocket   =   new   TIdSSLIOHandlerSocket(this);  
HTTP   =   new   TIdHTTP(this);  
HTTP->ReadTimeout   =   5000;  
HTTP->AllowCookies   =   true;  
HTTP->IOHandler   =   IOSocket;  
HTTP->CookieManager   =   Cookie;  
HTTP->ProtocolVersion   =   pv1_1;  
HTTP->HTTPOptions   <<   hoKeepOrigProtocol   <<   hoInProcessAuth   <<   hoForceEncodeParams;  

在OnNewCookie事件中保存ACookie.  
void   __fastcall   TfrmFireWall::CookieNewCookie(TObject   *ASender,  
TIdCookieRFC2109   *ACookie,   bool   &VAccept)  
{  
int   pos   =   ACookie->CookieText.Pos(";");  

if   (   pos   >   0   )  
FSessionID   =   ACookie->CookieText.SubString(   1,   pos   -1   );  
else  
FSessionID   =   ACookie->CookieText;  

}  

//登录：  
TStringStream   *Response;  
TStringStream   *Source;  
bool   rSuccess;  
AnsiString   URL,   User,   Password;  

User           =   usr;  
Password   =   pwd;  

Source   =   new   TStringStream("");  
Response   =   new   TStringStream("");  
HTTP->ReadTimeout   =   50000;  
try{  
try  
{  
URL   =   FUrl   +   LOGIN_CGI;  
Source->WriteString("username="   +   User   +   "&password="   +   Password);  
HTTP->Post(   URL,   Source,   Response   );  
Response->Position   =   0;  
Rtl   =   Response->DataString;  
if   (   Rtl   ==   ""   ){  
rSuccess   =   true;  
}else{  
rSuccess   =   false;  
if   (   Rtl.Pos("系统繁忙")   >   0   )  
{  
Status   =   "系统繁忙，请稍后登录";  
}  
else  
{  
Status   =   "登陆失败！请检查用户名、密码是否正确";  
}  
}  
}  
catch(   Exception   &exception   )  
{  
Status   =   exception.Message;  
rSuccess   =   false;  
Timer1->Enabled   =   false;  
}  
}   __finally{  
delete   Source;                                                                    
delete   Response;                
}  


//后续操作          
AnsiString   URL,   LinkHead;  
TStringList   *Source;  
TStringStream*   Response;  
URL   =   FUrl   +   cgi;  
Source   =   new   TStringList;  
Source->Text   =   Para;  
Response->Position   =   0;  
try{  
HTTP->ReadTimeout   =   OverTimeInterval;  
HTTP->Request->CustomHeaders->Add("Cookie:"   +   FSessionID);  
HTTP->Post(   URL,   Source,   Response   );  
if   (   Response->DataString.Pos("登录过时")   >   0   )  
{  
Timer1->Enabled   =   false;  
AnsiString   ErrInfo   =   "登录过时，请重新登录";  
}  
}  
catch(Exception   &exception){  
if   (   exception.Message   ==   "Read   Timeout"   )  
{  
Application->MessageBox(   exception.Message.c_str(),   "信息提示",   MB_OK   |   MB_ICONWARNING   );  
}else   if   (   exception.Message.Pos("400   Bad   Request")   >   0   )  
{  
}else{  
}  
}  
delete   Source;