Use OnCommandGet to handle HTTP client requests. Use the following parameters:
procedure OnCommandGet(AContext: TIdContext; ARequestInfo: TIdHTTPRequestInfo;
AResponseInfo: TIdHTTPResponseInfo);
begin
if ARequestInfo.Document = '/' then
begin
AResponseInfo.ContentText := '<html><head><title>Test Page</title></head><body></body></html>';
AResponseInfo.ContentType := 'text/html';
AResponseInfo.ResponseNo := 200;
end;
end;