Question/Problem/Abstract:

This procedure will switch on a machine that is connected to a LAN. The MAC address 
of the machine is needed to be known. 
See my article ("http://www.delphi3000.com/articles/article_3867.asp") for a 
function GetMacAddress() that returns a MAC Address String. 

The "Wake On Lan" feature of the machine's BIOS must be enabled. 

The procedure works by broadcasting a UDP packet containing the "Magic Number" to 
all machines on the LAN. The machine with the MAC address, if switched of and BIOS 
WOL enabled will wake up and boot. 

The MAC address required is a "-" delimited 17 char string. 
Example : 
1   
2   WakeOnLan('00-D0-B7-E2-A1-A0');

 
Answer:

3   
4   uses idUDPClient; 
5   
6   // ========================================================================== 
7   // Wakes a machine on lan 
8   // AMacAddress is 17 char MAC address. 
9   // eg.  '00-C0-4F-0A-3A-D7' 
10  // ========================================================================== 
11  
12  procedure WakeOnLan(const AMacAddress : string); 
13  type 
14       TMacAddress = array [1..6] of byte; 
15  
16       TWakeRecord = packed record 
17         Waker : TMACAddress; 
18         MAC   : array[0..15] of TMACAddress; 
19       end; 
20  
21  var i : integer; 
22      WR : TWakeRecord; 
23      MacAddress : TMacAddress; 
24      UDP : TIdUDPClient; 
25      sData : string; 
26  begin 
27    // Convert MAC string into MAC array 
28    fillchar(MacAddress,SizeOf(TMacAddress),0); 
29    sData := trim(AMacAddress); 
30  
31    if length(sData) = 17 then begin 
32      for i := 1 to 6 do begin 
33        MacAddress[i] := StrToIntDef('$' + copy(sData,1,2),0); 
34        sData := copy(sData,4,17); 
35      end; 
36    end; 
37  
38    for i := 1 to 6 do WR.Waker[i] := $FF; 
39    for i := 0 to 15 do WR.MAC[i] := MacAddress; 
40    // Create UDP and Broadcast data structure 
41    UDP := TIdUDPClient.Create(nil); 
42    UDP.Host := '255.255.255.255'; 
43    UDP.Port := 32767; 
44    UDP.BroadCastEnabled := true; 
45    UDP.SendBuffer(WR,SizeOf(TWakeRecord)); 
46    UDP.BroadcastEnabled := false; 
47    UDP.Free; 
48  end;