How can I get a computer's IP address?

Problem/Question/Abstract:

How can I get a computer's IP address ?

Answer:

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, Winsock;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    function DetectHostIP: Boolean;
  end;

const
  HostIP: string = 'Unknown';

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
begin
  DetectHostIP;
end;

//Detect own TCP/IP address

function TForm1.DetectHostIP: Boolean;
var
  wsdata: TWSAData;
  hostName: array[0..255] of char;
  hostEnt: PHostEnt;
  addr: PChar;
begin
  WSAStartup($0101, wsdata);
  try
    gethostname(hostName, sizeof(hostName));
    hostEnt := gethostbyname(hostName);
    if Assigned(hostEnt) then
      if Assigned(hostEnt^.h_addr_list) then
      begin
        addr := hostEnt^.h_addr_list^;
        if Assigned(addr) then
        begin
          HostIP := Format('%d.%d.%d.%d', [byte(addr[0]),
            byte(addr[1]), byte(addr[2]), byte(addr[3])]);
          Result := True;
        end
        else
          Result := False;
      end
      else
        Result := False
    else
    begin
      MessageDlg(Format('Winsock error %d', [WSAGetLastError]), mtError, [mbOk], 0);
      Result := False;
    end;
  finally
    WSACleanup;
  end
end;