Detecting the Remote Desktop Services(RDP) Environment

Detect Remote Desktop Services(RDP)

To optimize performance, it is good practice for applications to detect whether they are running in a Remote Desktop Services client session. For example, when an application is running on a remote session, it should eliminate unnecessary graphic effects, as described in Graphic Effects. If the user is running the application in a local environment, it is not as critical for the application to optimize its behavior.

The following example shows a function that returns TRUE if the application is running in a remote session and FALSE if the application is running on the console.

sample code:

#include windows.h

#pragma comment(lib, "user32.lib")

BOOL IsRemoteSession(void)

{

return GetSystemMetrics( SM_REMOTESESSION );

}

ref:

http://msdn.microsoft.com/en-us/library/aa380798

code to detect if an application is running under terminal server -

http://stackoverflow.com/questions/295415/how-do-i-tell-if-my-application-is-running-in-an-rdp-session

How to test the reachability of a VPN-Connection? -

http://www.codeproject.com/KB/IP/SimpleLineTester.aspx

Detect Internet Connection

Actually, there is no single function for determining if a machine is  connected to the Internet, and it is impossible to reliably determine what  is happening without side effects - such as automatic network connections  taking place. What you can do is reliably detect when there definitely  isn't an Internet Link: in the absence of any dial up or LAN connection the  system is definitely off line.   

Some techniques include:  

1. IsNetworkAlive() If you are targeting system with IE5 or later, this is the best API call  yet it even listens for traffic on a LAN. There is a secondary function  IsDestinationReachable() which tries to resolve the hostname and ping it.  This does not work through firewalls, and overestimates speed as the max  the LAN card can support, rather than the actual point to point bandwidth.  

2. RasEnumConnections() A reliable technique for modems and direct dial up networking, but not for  situations where Internet access is via a LAN. You should dynamically load  "RasEnumConnectionA" from "RASAPI32.DLL", as LAN installations of Windows  may not include the library.  

3. InternetGetConnectedState() This Wininet /IE4 function call can distinguish between modem and LAN, but  can't handle complex LAN+autodial router situations. It is "offline state  aware". Important: handling of the offline flage changed for IE5 -it  returns TRUE for connected'  even when off line, but signals the flags in  the LPDWORD parameter.  

4. InternetCheckConnection() A Winnet/IE4 function call. This is meant to determine if a URL is  reachable- in practice it is pretty unreliable and best voided.  

5. NT SP4, NT5: The IP helper API can tell you which network interface to  use to connect to a supplied IP address, and what the bandwidth and current  status of that link is  

6. Using the Offline flag which is part of IE4 to allow users to manually  control the online/offline state of applications. This flag is stored in  the registry and can be manipulated via some funcions calls  These calls mostly determine the presence or absence of network connections  -not Internet access, so can't handle a home network sharing a dial up  connection, or two laptops connected directly to each other.   The global offline state flag of IE4 (and hence win98, NT5) and the call to  test it - InternetGetConnectedState()- look the best long term options, but  will take time to become universal. The IP Helper APIs even let you find  out how much traffic is going over a link, but only detect the 'loopback'  interface on Windows 98, so is not a lot of use. Wouldn't a  'GetSpeedToHost() function call be great?   

Finally, whatever technique you use, when it's time to talk to a remote  site, always add timeouts or a cancel button. Even a quick functions like  gethostbyname() can lock up an app if something in the network chain is  broken.  

ref:

How to test the reachability of a VPN-Connection? - http://www.codeproject.com/KB/IP/SimpleLineTester.aspx

Get UserName from SessionId

#include windows.h

#include vector

#include string

#include wtsapi32.h

#pragma comment(lib, "WtsApi32.lib")

//
typedef std::basic_string tstring;

// Get current sessions
bool EnumSessionIds(std::vector& list)
{
list.clear();

WTS_SESSION_INFO *pSI = NULL;
DWORD dwSICount;

BOOL bRes = WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE, 0, 1, &pSI, &dwSICount);
if (bRes == 0)
return false;

for (unsigned int i = 0; i < pbuffer =" NULL;" bres =" WTSQuerySessionInformation(WTS_CURRENT_SERVER_HANDLE," bres ="=" username =" pBuffer;" pbuffer =" NULL;" bres =" WTSQuerySessionInformation(WTS_CURRENT_SERVER_HANDLE," bres ="=" domain =" pBuffer;"> sessionIds;
bool bRes = EnumSessionIds(sessionIds);
if (!bRes)
{
// error
return 0;
}

// enum sessions
std::vector::iterator iter;
for (iter = sessionIds.begin(); iter != sessionIds.end(); iter++)
{
// print session domain
tstring domain;
GetSessionDomain(*iter, domain);
_tprintf(_T("Session Domain = %s\n"), domain.c_str());

// print session username
tstring username;
GetSessionUserName(*iter, username);
_tprintf(_T("Session UserName = %s\n"), username.c_str());
}

return 0;
}

ref:

Windows-based application over Terminal Services using WtsAPI32 -

http://www.codeproject.com/KB/winsdk/LiviuBirjegaCode3.aspx

REST vs SOAP

SOAP (Simple Object Access Protocol) and REST (Representational State Transfer) provide mechanisms for requesting information from endpoints (SOAP) or from resources (REST). Perhaps the best way to think of these technologies is as a method of making a remote procedure calls against a well-defined API. SOAP has a more formal definition mechanism called WSDL (Web Services Definition Language) and is a bit more complex to implement. REST uses the standard HTTP request and response mechanism, simplifying implementation and providing for a looser coupling of the client and server. Note that REST also supports the transfer of non-XML messages such as JSON (JavaScript Object Notation

Which is better, REST or SOAP?

This is one of the most common questions I get about REST, and it is probably the least fair. Both REST and SOAP are often termed "Web services," and one is often used in place of the other, but they are totally different approaches. REST is an architectural style for building client-server applications. SOAP is a protocol specification for exchanging data between two endpoints.

Comparing REST with the remote procedure call (RPC) style of building client-server applications would be more accurate. RPC is a style (rather than a protocol, which is what SOAP is) of building client-server applications in which a proxy (generally generated from metadata) is used in the client's address space to communicate with the server and the proxy's interface mimics the server's interface. Although SOAP doesn't require the RPC style, most modern SOAP toolkits are geared toward (at least they default to) using RPC.

In contrast to RPC, REST lacks the metadata-generated proxy (see the next question for more information), which means that the client is less coupled to the service. Also, because REST relies on the semantics of HTTP, requests for data (GET requests) can be cached. RPC systems generally have no such infrastructure (and even when performing RPC using SOAP over HTTP, SOAP responses can't be cached because SOAP uses the HTTP POST verb, which is considered unsafe). SOAP intentionally eschews HTTP, specifically to allow SOAP to work over other protocols, so it's actually a little disingenuous to call SOAP-based services Web services.

My perspective is that both REST and SOAP can be used to implement similar functionality, but in general SOAP should be used when a particular feature of SOAP is needed, and the advantages of REST make it generally the best option otherwise.

ref:

Rest vs Soap -

http://blogs.msdn.com/b/swiss_dpe_team/archive/2008/11/28/rest-vs-soap.aspx

http://msdn.microsoft.com/en-us/magazine/dd942839.aspx

Soap vs Rest discussions - http://blogs.msdn.com/b/zainnab/archive/2007/12/16/rest-vs-soap-decision-decisions-decisions.aspx

Introduction to Restful Webservices - http://msdn.microsoft.com/en-us/magazine/dd315413.aspx

Web Services, Part 1: SOAP vs. REST - http://www.ajaxonomy.com/2008/xml/web-services-part-1-soap-vs-rest

Stefan Tilkov: REST vs SOAP - http://www.innoq.com/blog/st/2006/06/30/rest_vs_soap_oh_no_not_again.html

Roots of REST vs SOAP - http://www.prescod.net/rest/rest_vs_soap_overview/

REST vs SOAP from StackOverflow -http://stackoverflow.com/questions/209905/rest-and-soap

Giving SOAP a REST -http://www.devx.com/DevX/Article/8155

Http Message Length

The transfer-length of a message is the length of the message-body as it appears in the message; that is, after any transfer-codings have been applied. When a message-body is included with a message, the transfer-length of that body is determined by one of the following (in order of precedence):

1.Any response message which "MUST NOT" include a message-body (such as the 1xx, 204, and 304 responses and any response to a HEAD request) is always terminated by the first empty line after the header fields, regardless of the entity-header fields present in the message.

2.If a Transfer-Encoding header field (section 14.41) is present and has any value other than "identity", then the transfer-length is defined by use of the "chunked" transfer-coding (section 3.6), unless the message is terminated by closing the connection.

3.If a Content-Length header field (section 14.13) is present, its decimal value in OCTETs represents both the entity-length and the transfer-length. The Content-Length header field MUST NOT be sent if these two lengths are different (i.e., if a Transfer-Encoding

     header field is present). If a message is received with both a      Transfer-Encoding header field and a Content-Length header field,      the latter MUST be ignored. 

4.If the message uses the media type "multipart/byteranges", and the transfer-length is not otherwise specified, then this self- delimiting media type defines the transfer-length. This media type MUST NOT be used unless the sender knows that the recipient can parse it; the presence in a request of a Range header with multiple byte- range specifiers from a 1.1 client implies that the client can parse multipart/byteranges responses.

       A range header might be forwarded by a 1.0 proxy that does not        understand multipart/byteranges; in this case the server MUST        delimit the message using methods defined in items 1,3 or 5 of        this section. 

5.By the server closing the connection. (Closing the connection cannot be used to indicate the end of a request body, since that would leave no possibility for the server to send back a response.)

For compatibility with HTTP/1.0 applications, HTTP/1.1 requests containing a message-body MUST include a valid Content-Length header field unless the server is known to be HTTP/1.1 compliant. If a request contains a message-body and a Content-Length is not given, the server SHOULD respond with 400 (bad request) if it cannot determine the length of the message, or with 411 (length required) if it wishes to insist on receiving a valid Content-Length.

All HTTP/1.1 applications that receive entities MUST accept the "chunked" transfer-coding (section 3.6), thus allowing this mechanism to be used for messages when the message length cannot be determined in advance.

Messages MUST NOT include both a Content-Length header field and a non-identity transfer-coding. If the message does include a non- identity transfer-coding, the Content-Length MUST be ignored.

When a Content-Length is given in a message where a message-body is allowed, its field value MUST exactly match the number of OCTETs in the message-body. HTTP/1.1 user agents MUST notify the user when an invalid length is received and detected.

Chunked transfer encoding

From Wikipedia, the free encyclopedia

Chunked transfer encoding is a data transfer mechanism in the Hypertext Transfer Protocol (HTTP) that allows HTTP data to be reliably delivered between a web server and a clientapplication, usually a web browser, without knowing in advance of transmission the size of the entire message body. This is achieved by splitting the data payload of the message in small parts (chunks) and transmitting with each chunk its size. The data transfer is terminated by a final chunk of length zero. This makes it possible to transmit dynamically generated content in web pages. The chunked method is only available in version 1.1 of the HTTP protocol (HTTP/1.1).

Without chunked transfer encoding, the size of data delivered in HTTP responses must be indicated by the Content-Length header field to allow clients to determine the end of transmission.

Format

If a Transfer-Encoding field with a value of chunked is specified in an HTTP message (either a request sent by a client or the response from the server), the body of the message consists of an unspecified number of chunks, a terminating last-chunk, an optional trailer of entity-header fields, and a final CRLF sequence.

Each chunk starts with the number of octets of the data it embeds expressed in hexadecimal followed by optional parameters (chunk extension) and a terminating CRLF (carriage returnand line feed) sequence, followed by the chunk data. The chunk is terminated by CRLF. If chunk extensions are provided, the chunk size is terminated by a semicolon followed with the extension name and an optional equal sign and value.

The last chunk is a zero-length chunk, with the chunk size coded as 0, but without any chunk data section.

The final chunk may be followed by an optional trailer of additional entity-header fields that are normally delivered in the HTTP header to allow the delivery of data that can only be computed after all chunk data has been generated. The sender may indicate in a Trailer header field which additional fields it will send in the trailer after the chunks.

[edit]Example

[edit]Encoded response

HTTP/1.1 200 OK Content-Type: text/plain Transfer-Encoding: chunked  25 This is the data in the first chunk  1C and this is the second one  3 con 8 sequence 0  

[edit]Anatomy of encoded response

The first two chunks contain explicit \r\n characters in the chunk data.

"This is the data in the first chunk\r\n"      (37 chars => hex: 0x25) "and this is the second one\r\n"               (28 chars => hex: 0x1C) "con"                                          (3  chars => hex: 0x03) "sequence"                                     (8  chars => hex: 0x08) 

The response ends with a zero-length last chunk: "0\r\n" and the final "\r\n".

[edit]Decoded data

This is the data in the first chunk and this is the second one consequence