How to get Client IP Address?

31 Oct

When a client is connected to a Terminal Server Session you can use the Terminal Server API to retrieve the client’s local IP address.

Start by enumerating all sessions with WtsEnumerateSessions and then for each session get the ClientAddress with a call to WTSQuerySessionInformation with the WTSClientAddress parameter. Sound simple, no?

WTSQuerySessionInformation returns a pointer to a WTS_CLIENT_ADDRESS structure. You need to know that the IP address is located at on offset of 2 bytes in the Address member of WTS_CLIENT_ADDRESS.

So here’s a sample:

uses JwaWinType, JwaWtsApi32, JwaWinsock2, ExtCtrls;
type
  PWtsSessionInfoAArray = ^TWtsSessionInfoAArray;
  TWtsSessionInfoAArray = array[0..ANYSIZE_ARRAY-1] of WTS_SESSION_INFOA;

var hServer: THandle;
  SessionInfoPtr: PWtsSessionInfoAArray;
  pCount: Cardinal;
  ClientAddressPtr: PWtsClientAddress;
  dwBytesReturned: Cardinal;
  IPStr: String;
  i: integer;
begin
  if WtsEnumerateSessions(WTS_CURRENT_SERVER, 0, 1, PWTS_SESSION_INFO(SessionInfoPtr), 
    pCount) then
  begin

    for i := 0 to pCount - 1 do
    begin
      WTSQuerySessionInformation(WTS_CURRENT_SERVER, SessionInfoPtr^[i].SessionId, 
        WTSClientAddress, Pointer(ClientAddressPtr), dwBytesReturned);
      case ClientAddressPtr^.AddressFamily of
        AF_INET:
          IPStr:= Format('%d.%d.%d.%d', [ClientAddressPtr^.Address[2],
            ClientAddressPtr^.Address[3], ClientAddressPtr^.Address[4],
            ClientAddressPtr^.Address[5]]);
          AF_INET6:
            IPStr:= 'IPv6 address not yet supported';
          AF_IPX:
            IPStr:= 'IPX is not supported';
          AF_NETBIOS:
            IPStr:= 'NETBIOS is not supported';
          AF_UNSPEC:
            IPStr:= 'Unspecified (console and listener session have no address)';
      end;

      WTSfreeMemory(ClientAddressPtr);
    end;
  end;

  // Don't close the handle if it's WTS_CURRENT_SERVER
  WtsFreeMemory(SessionInfoPtr);
end;

uses JwaWinType, JwaWtsApi32, JwaWinsock2, ExtCtrls;

type

PWtsSessionInfoAArray = ^TWtsSessionInfoAArray;

TWtsSessionInfoAArray = array[0..ANYSIZE_ARRAY-1] of WTS_SESSION_INFOA;

var hServer: THandle;

SessionInfoPtr: PWtsSessionInfoAArray;

pCount: Cardinal;

ClientAddressPtr: PWtsClientAddress;

dwBytesReturned: Cardinal;

IPStr: String;

i: integer;

begin

if WtsEnumerateSessions(WTS_CURRENT_SERVER, 0, 1, PWTS_SESSION_INFO(SessionInfoPtr),

pCount) then

begin

for i := 0 to pCount - 1 do

begin

WTSQuerySessionInformation(WTS_CURRENT_SERVER, SessionInfoPtr^[i].SessionId,

WTSClientAddress, Pointer(ClientAddressPtr), dwBytesReturned);

case ClientAddressPtr^.AddressFamily of

AF_INET:

IPStr:= Format('%d.%d.%d.%d', [ClientAddressPtr^.Address[2],

ClientAddressPtr^.Address[3], ClientAddressPtr^.Address[4],

ClientAddressPtr^.Address[5]]);

AF_INET6:

IPStr:= 'IPv6 address not yet supported';

AF_IPX:

IPStr:= 'IPX is not supported';

AF_NETBIOS:

IPStr:= 'NETBIOS is not supported';

AF_UNSPEC:

IPStr:= 'Unspecified (console and listener session have no address)';

end;

WTSfreeMemory(ClientAddressPtr);

end;

// Don't close the handle if it's WTS_CURRENT_SERVER

WtsFreeMemory(SessionInfoPtr);

end;

Screenshot:
Client IP demo app screenshot
ClientIP.zip (3686 downloads)

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Filed under: Delphi, Programming, Terminal Server

8 Responses for "How to get Client IP Address?"

Remko November 1st, 2007 at 10:44 1
The code was somehow messed up when I pasted it in WordPress. It should be ok now. I also added a little demo app with source.
Arnout November 1st, 2007 at 11:02 2
Thanks! This works very nicely
bora August 17th, 2009 at 16:54 3
Where are units, JwaWinType, JwaWtsApi32, JwaWinsock2? Could not find it anywhere 🙁
Lanis September 7th, 2009 at 9:17 4
search with google.
Remko September 18th, 2009 at 11:46 5
@Bora: Lanis is right, Google would have found you the answer: http://blog.delphi-jedi.net/jedi-api-headers/
Serg February 10th, 2011 at 13:02 6
Unfortunately I got always 73.0.0.0 or 0.0.0.0 when I connect to PS via TS gateway, if I connect directly to PC I got the proper client IP.
Is there any solution to get client IP (via TS gateway) or TS gateway does hide it?
JoeE April 15th, 2011 at 15:28 7
Thanks a lot!
But how to get the local IP within a session?
I need only the ip from my own session.
Remko April 15th, 2011 at 18:36 8
@JoeE: check out my answer to this question on stackoverflow: http://stackoverflow.com/questions/576538/delphi-how-to-get-all-local-ips/1116526#1116526