idhttp->AllowCookies =true;
idhttp->HandleRedirects =true; //允许重定向
idhttp->ConnectTimeout =20000;
idhttp->ReadTimeout =20000;
//hoInProcessAuth, hoKeepOrigProtocol, hoForceEncodeParams, hoNonSSLProxyUseConnectVerb, hoNoParseMetaHTTPEquiv, hoWaitForUnexpectedData, hoTreat302Like303, hoNoProtocolErrorException, hoNoReadMultipartMIME, hoNoParseXmlCharset, hoWantProtocolErrorContent, hoNoReadChunked
idhttp->HTTPOptions <<hoKeepOrigProtocol;
//pv1_0, pv1_1
idhttp->ProtocolVersion =pv1_1;
//sslvSSLv2, sslvSSLv23, sslvSSLv3, sslvTLSv1, sslvTLSv1_1, sslvTLSv1_2
SSLIO->SSLOptions->Method = sslvTLSv1_2;
//sslmUnassigned, sslmClient, sslmServer, sslmBoth
SSLIO->SSLOptions->Mode = sslmClient;
SSLIO->ConnectTimeout =20000;
idhttp->IOHandler=SSLIO;
idhttp->Request->ContentType="text/xml";
idhttp->Request->Username =user;
idhttp->Request->Password =pass;
idhttp->Request->BasicAuthentication =true;
如果使用“基本验证”方案，凭证通过如下步骤生成：
用冒号将用户名和密码进行拼接（如：user:pass）。
将第一步生成的结果用 base64 方式编码(XXXXXX)。
拼接Base XXXXXX
注意: Base64编码并不是一种加密方法或者hashing方法！这种方法的安全性与明文发送等同（base64可以逆向解码）。“基本验证”方案需要与HTTPS协议配合使用。
原文：https://www.cnblogs.com/suhq/p/13739943.html