unit Unit1;

interface

uses
 Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
 Dialogs, ExtCtrls, Sockets, StdCtrls, IdBaseComponent, IdComponent,
 IdUDPBase, IdUDPServer,Idglobal,IdSocketHandle;

type
 TForm1 = class(TForm)
   ListBox1: TListBox;
   Timer1: TTimer;
   IdUDPServer1: TIdUDPServer;
   procedure Timer1Timer(Sender: TObject);
   procedure IdUDPServer1UDPRead(AThread: TIdUDPListenerThread;
     AData: TIdBytes; ABinding: TIdSocketHandle);
   procedure FormShow(Sender: TObject);
 private
   { Private declarations }
 public
   { Public declarations }
 end;

var
 Form1: TForm1;

implementation

{$R *.dfm}
const
 PS1='Ya tut';
 PS2='Gde vse';
 N=4;

procedure TForm1.FormShow(Sender: TObject);
begin
 IdUDPServer1.Broadcast(PS2,IdUDPServer1.DefaultPort);
end;

procedure TForm1.Timer1Timer(Sender: TObject);
var i,t:integer;
begin
 for i:=ListBox1.Items.Count-1 downto 0 do
 begin
   t:=StrToIntDef(ListBox1.Items.ValueFromIndex[i],0);
   dec(t,Timer1.Interval div 1000);
   if t<=0 then
     ListBox1.Items.Delete(i)
   else
     ListBox1.Items.ValueFromIndex[i]:=IntToStr(t);
 end;
 IdUDPServer1.Broadcast(PS1,IdUDPServer1.DefaultPort);
end;

procedure TForm1.IdUDPServer1UDPRead(AThread: TIdUDPListenerThread;
 AData: TIdBytes; ABinding: TIdSocketHandle);
var SData:string;
begin
 SetString(SData,PChar(@AData[0]),Length(AData));
 if SData=PS1 then
   ListBox1.Items.Values[ABinding.PeerIP]:=IntToStr(Timer1.Interval*N div 1000);
 if SData=PS2 then
 begin
   ListBox1.Items.Values[ABinding.PeerIP]:=IntToStr(Timer1.Interval*N div 1000);
   IdUDPServer1.Send(ABinding.PeerIP,IdUDPServer1.DefaultPort,PS1);
 end;
end;

end.

program UDP;

{$APPTYPE CONSOLE}

uses
 SysUtils,WinSock,Windows;

resourcestring
 sWindowsSocketError = 'Windows socket error: %s (%d), on API ''%s''';
procedure RaiseSocketError(const Op: string);
var Error:integer;
begin
 Error := WSAGetLastError;
 raise Exception.CreateResFmt(@sWindowsSocketError, [SysErrorMessage(Error), Error, Op]);
end;

procedure WriteLnEx(const Text:string;color:byte=FOREGROUND_GREEN);
var
 hStdOut:THandle;
 BufferInfo:TConsoleScreenBufferInfo;
 Result:DWORD;
 Attrs: array of word;
 i:integer;
begin
 hStdOut:=GetStdHandle(STD_OUTPUT_HANDLE);
 Win32Check(GetConsoleScreenBufferInfo(hStdOut,BufferInfo));
 SetLength(Attrs, Length(Text));
 for I:=low(Attrs) to high(Attrs) do Attrs[I]:=color;
 Writeln(Text);
 Win32Check(WriteConsoleOutputAttribute(hStdOut, @Attrs[0], Length(Text), BufferInfo.dwCursorPosition, Result));
end;

procedure RecvLoop(sock: TSocket);
const BufSize:integer=$ffff;
var
 buf: PChar;
 from: TSockAddr;
 Size,fromlen: integer;
begin
 fromlen:=SizeOf(TSockAddr);
 GetMem(buf, bufsize);
 try
   while true do
   begin
     Size:=recvfrom(sock, buf^, BufSize, 0, from, fromlen);
     if Size<> SOCKET_ERROR then
     begin
       WriteLnEx(inet_ntoa(from.sin_addr)+':'+inttostr(ntohs(from.sin_port))+' write:');
       WriteConsole(GetStdHandle(STD_OUTPUT_HANDLE), buf, dword(Size), dword(Size), nil);
     end else RaiseSocketError('recvfrom');
   end;
 finally
   FreeMem(buf);
 end;
end;

var
 WSAData: TWSAData;
 sock:TSocket;
 addr:TSockAddrIn;
begin
 WSAStartup(MakeWord(1, 0), WSAData);
 sock:=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
 addr.sin_family:= AF_INET;
 addr.sin_addr.S_addr:= htonl(INADDR_ANY);
 addr.sin_port:= htons(3052);
 WriteLnEx('Listening '+inttostr(ntohs(addr.sin_port))+' port...',FOREGROUND_RED);
 bind(sock, addr, SizeOf(addr));
 RecvLoop(sock);
 closesocket(sock);
 WSACleanup;
end.

WSAStartup($101,Init);
Sock:=Socket(PF_INET,SOCK_DGRAM,IPPROTO_UDP);
SockOpt:=TRUE;
SetSockOpt(Sock,SOL_SOCKET,SO_BROADCAST,PChar(@SockOpt),SizeOf(SockOpt));
Target.sin_port:=htons(5353);
Target.sin_addr.S_addr:=INADDR_BROADCAST;
Target.sa_family:=AF_INET;

Data:='Any string';
SendTo(Sock,Data,Length(Data),0,Target,SizeOf(Target));

CloseSocket(Sock);
WSACleanup;

SendTo(Sock,PChar(Data)^,Length(Data),0,Target,SizeOf(Target));