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How to get programmatically the LAN servers IP address my application is started from

Posted on 2009-04-07
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Last Modified: 2013-12-03
I want programmatically determine the IP address of the LAN server in a application that is started on a client but whose exe file resides on the server. So I don't want the IP address of the PC the application is running on (client) but is started from (server).
Can somebody help with some code. Delphi is preferred but any other programming language is also appreciated.

Thanks, Bruno

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Question by:Bruno Buesser
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by:jkr
ID: 24089493
That will depend - are you starting the app via an UNC path or from a mapped drive?
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by:Bruno Buesser
ID: 24094405
That depends on the customer who installs the application. So I think I should have a solution for both UNC and mapped drive.
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jkr earned 250 total points
ID: 24097860
For UNC paths, that is quite simple - just extract the server name from that path (i.e. the name between '\\' and the next following backslash) and call 'gethostbyname()' to obtain the IP address. For a mapped drive, things are more difficult. You have to obtain the drive letter first and look that one up from the information returned by 'NetUseEnum()' (see e.g. http://win32.mvps.org/network/nusee.cpp on how to use that) to get the share's UNC path from 'ui2_remote' in 'USE_INFO_2' and proceed as above. Alternatively, you could also do that using 'WNetEnumResource()' (http://win32.mvps.org/network/wnoe_wner.c).
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by:Bruno Buesser
ID: 24226214
That's my Delphi solution:


function GetComputerName: string;
var
  ComputerName: array[0..MAX_COMPUTERNAME_LENGTH+1] of Char;
  Size: DWORD;
begin
  Size:=MAX_COMPUTERNAME_LENGTH+1;
  if Windows.GetComputerNameA(ComputerName, Size) then
     Result:= ComputerName
  else
     Result:= '';
end;
 
function GetHostIP: string;
{ Get IP from Computer my applicatio is started from.
  Returns an empty string in case of errors
 
  ParamStr(0) may have 3 different path types:
  1. Local path:       C:\mydirectory\myapplication.exe
  2. Mapped drive:     O:\<sharename>\mydirectory\myapplication.exe
  3. UNC Network path: \\<servername>\<sharename>\mydirectory\myapplication.exe
}
var
  S: string;
  ServerName: string;
  WSAData: TWSAData;
  HostEnt: PHostEnt;
  Index: Integer;
begin
  ServerName:= '';
 
  S:= ExpandUNCFileName(ParamStr(0));  // Returns also UNC path for mapped drives
  if Pos('\\',S) > 0 then
  begin
    S:= Copy(S,3,Length(S)-3);
    Index:= Pos('\',S);
    if Index > 0 then
      ServerName:= Copy(S,1,Index-1);
  end else
    ServerName:= GetComputerName;
 
 
  if ServerName <> '' then
  begin
    HostEnt:= GetHostByName(PChar(ServerName));
    WSAStartup(2, WSAData);
    try
      with HostEnt^ do
        Result:= Format('%d.%d.%d.%d',[Byte(h_addr^[0]),Byte(h_addr^[1]),Byte(h_addr^[2]),Byte(h_addr^[3])]);
    finally
      WSACleanup;
    end;
  end else
    Result:= '';
end;

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by:jkr
ID: 24226669
Thanks for sharing!
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