How to get the local IP address using Inno Setup

Build an external DLL that returns a list of IP addresses and read that list in Inno Setup script.

In this article you will find code example how to build a DLL and how to call it in the InnoSetup script.

In this SO post you will find how to get IP addresses using Indy library or plain WinApi.

It depends on if you want IPv4 address or the IPv6 address. But since you mentioned GetIpAddrTable and it only returns IPv4 addresses, I suspect that is what you wanted.

Each machine can have more than one local IP address. So I return them as a TStringList.
The machine I tested the following on had 5 IP addresses.

Since Inno Setup does not support pointers, I had to do everything through an Array of Byte for the buffer.

The code below is a complete Inno Setup script that demonstrates, how to use this function.

[Setup]
AppName=Test
AppVersion=1.5
DefaultDirName={pf}\test

[Code]

const
 ERROR_INSUFFICIENT_BUFFER = 122;


function GetIpAddrTable( pIpAddrTable: Array of Byte;
  var pdwSize: Cardinal; bOrder: WordBool ): DWORD;
external '[email protected] stdcall';


procedure GetIpAddresses(Addresses : TStringList);
var 
 Size : Cardinal;
 Buffer : Array of Byte;
 IpAddr : String;
 AddrCount : Integer;
 I, J : Integer;
begin
  { Find Size }
  if GetIpAddrTable(Buffer,Size,False) = ERROR_INSUFFICIENT_BUFFER then
  begin
     { Allocate Buffer with large enough size }
     SetLength(Buffer,Size);
     { Get List of IP Addresses into Buffer }
     if GetIpAddrTable(Buffer,Size,True) = 0 then
     begin
       { Find out how many addresses will be returned. }
       AddrCount := (Buffer[1] * 256) + Buffer[0];
       { Loop through addresses. }
       For I := 0 to AddrCount - 1 do
       begin
         IpAddr := '';
         { Loop through each byte of the address }
         For J := 0 to 3 do
         begin
           if J > 0 then
             IpAddr := IpAddr + '.';
           { Navigate through record structure to find correct byte of Addr }
           IpAddr := IpAddr + IntToStr(Buffer[I*24+J+4]);
         end;
         Addresses.Add(IpAddr);
       end;
     end;
  end;
end;

function InitializeSetup(): Boolean;
var
 SL : TStringList;
begin
  SL := TStringList.Create;
  GetIpAddresses(SL);
  MsgBox(SL.Text, mbInformation, MB_OK);
  SL.Free;
end;