AThread

var
  List: TList;
  Peer: TIdPeerThread;
...
  List := IdTCPServer1.Threads.LockList; //isso bloqueia o servidor!
  try
    for I := 0 to List.Count - 1 do begin
      // List[I] é uma das threads do servidor
      Peer := TIdPeerThread(List[I]);
      Peer.Connection.WriteLn(´Oi´);
    end;
  finally
    IdTCPServer1.Threads.UnlockList
  end;

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, IdThreadMgr, IdThreadMgrDefault, IdBaseComponent,
  IdComponent, IdTCPServer;

type
  TForm1 = class(TForm)
    TCPServer: TIdTCPServer;
    Memo: TMemo;
    Button1: TButton;
    ThreadMgr: TIdThreadMgrDefault;
    procedure TCPServerConnect(AThread: TIdPeerThread);
    procedure FormShow(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure TCPServerDisconnect(AThread: TIdPeerThread);
  private
    { Private declarations }
  public
    Thread: TList;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormShow(Sender: TObject);
begin
TCPServer.Active:= True;
end;

procedure TForm1.TCPServerConnect(AThread: TIdPeerThread);
begin
Thread.Add(AThread);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
i: Integer;
begin
Memo.Lines.Clear;
for i:= 0 to Thread.Count-1 do
Memo.Lines.Add(TIdPeerThread(Thread[i]).Connection.Socket.Binding.PeerIP);
end;

procedure TForm1.TCPServerDisconnect(AThread: TIdPeerThread);
begin
Thread.Remove(AThread);
end;

end.

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, IdBaseComponent, IdComponent, IdTCPConnection,
  IdTCPClient, IdAntiFreezeBase, IdAntiFreeze;

type
  TForm_Principal = class(TForm)
    TCPClient: TIdTCPClient;
    IP: TEdit;
    Button1: TButton;
    AntiFreeze: TIdAntiFreeze;
    Memo: TMemo;
    procedure Button1Click(Sender: TObject);
    procedure TCPClientConnected(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

  TClientThread = class(TThread)
  protected
    procedure Execute; override;
  public
    constructor Create(CreateSuspended: Boolean);
  end;

var
  Form_Principal: TForm_Principal;

implementation

{$R *.dfm}

procedure TForm_Principal.Button1Click(Sender: TObject);
begin
TCPClient.Host:= IP.Text;
TCPClient.Connect;
end;


constructor TClientThread.Create(CreateSuspended: Boolean);
begin
inherited Create(CreateSuspended);
Priority := tpIdle;
FreeOnTerminate:= true;
end;

procedure TClientThread.Execute;
begin
inherited;
with Form_Principal do
begin
if not TCPClient.Connected then
exit;
repeat
Form_Principal.Memo.Lines.Add(TCPClient.ReadLn);
until not TCPClient.Connected;
end;
end;

procedure TForm_Principal.TCPClientConnected(Sender: TObject);
begin
TClientThread.Create(false);
end;

end.