ClientSocket組件為客戶端組件。它是通信的請求方，也就是說，它是主動地與服務器端建立連接。

ServerSocket組件為服務器端組件。它是通信的響應方，也就是說，它的動作是監聽以及被動接受客戶端的連接請求，并對請求進行回復。

【以下內容轉自http://blog.csdn.net/dainiao01/article/details/2694257】
本例包括一個服務器端程序和一個客戶端程序。客戶端程序可以放到多個計算機上運行，同時與服務器端進行連接
通信。

本例的重點，一是演示客戶端與服務器端如何通信；二是當有多個客戶端同時連接到服務器端時，服務器端如何識
別每個客戶端，并對請求給出相應的回復。為了保證一個客戶端斷開連接時不影響其它客戶端與服務器端的通信，
同時保證服務器端能夠正確回復客戶端的請求，在本例中聲明了一個記錄類型：

服務器端源碼（uServerMain.pas）：

unit uServerMain;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
ScktComp, ToolWin, ComCtrls, ExtCtrls, StdCtrls, Buttons;

const
CMax=10; //客戶端最大連接數

type
client_record=record
CHandle: integer; //客戶端套接字句柄
CSocket:TCustomWinSocket; //客戶端套接字
CName:string; //客戶端計算機名稱
CAddress:string; //客戶端計算機IP地址
CUsed: boolean; //客戶端聯機標志

end;

type
  TfrmServerMain = class(TForm)
  ServerSocket: TServerSocket;
  ControlBar1: TControlBar;
  ToolBar1: TToolBar;
  tbConnect: TToolButton;
  tbClose: TToolButton;
  tbDisconnected: TToolButton;
  Edit1: TEdit;
  Memo1: TMemo;
  StatusBar: TStatusBar;
  procedure tbConnectClick(Sender: TObject);
  procedure tbDisconnectedClick(Sender: TObject);
  procedure ServerSocketClientRead(Sender: TObject;
  Socket: TCustomWinSocket);
  procedure ServerSocketListen(Sender: TObject;
  Socket: TCustomWinSocket);
  procedure ServerSocketClientConnect(Sender: TObject;  Socket: TCustomWinSocket);
  procedure ServerSocketClientDisconnect(Sender: TObject;  Socket: TCustomWinSocket);
  procedure tbCloseClick(Sender: TObject);
  procedure FormCreate(Sender: TObject);
  procedure FormClose(Sender: TObject; var Action: TCloseAction);
  procedure ServerSocketGetSocket(Sender: TObject; Socket: Integer;  var ClientSocket: TServerClientWinSocket);
  procedure ServerSocketClientError(Sender: TObject;  Socket: TCustomWinSocket; ErrorEvent: TErrorEvent;  var ErrorCode: Integer);
  
  private
    { Private declarations }
  public
    { Public declarations }
    session: array[0..CMax] of client_record; //客戶端連接數組
    Sessions: integer; //客戶端連接數
end;

var
  frmServerMain: TfrmServerMain;

implementation
{$R *.DFM}

//打開套接字連接，并使套接字進入監聽狀態
procedure TfrmServerMain.tbConnectClick(Sender: TObject);
begin
  ServerSocket.Open ;
end;

//關閉套接字連接，不再監聽客戶端的請求
procedure TfrmServerMain.tbDisconnectedClick(Sender: TObject);
begin
  ServerSocket.Close;
  StatusBar.Panels[0].Text :=服務器套接字連接已經關閉，無法接受客戶端的連接請求.;
end;

//從客戶端讀取信息
procedure TfrmServerMain.ServerSocketClientRead(Sender: TObject; 
 Socket: TCustomWinSocket);
var
  i:integer;
begin
  //將從客戶端讀取的信息添加到Memo1中
  Memo1.Lines.Add(Socket.ReceiveText);
  for i:=0 to sessions do
  begin
    //取得匹配的客戶端
    if session[i].CHandle = Socket.SocketHandle then
    begin
      session[i].CSocket.SendText(回復客戶端+session[i].CAddress+ ==> +Edit1.Text);
    end;
  end;
end;

//服務器端套接字進入監聽狀態，以便監聽客戶端的連接
procedure TfrmServerMain.ServerSocketListen(Sender: TObject;
Socket: TCustomWinSocket);
begin
    StatusBar.Panels[0].Text :=等待客戶端連接...;
end;
//當客戶端連接到服務器端以后
procedure TfrmServerMain.ServerSocketClientConnect(Sender: TObject;
Socket: TCustomWinSocket);
var
i,j:integer;
begin
j:=-1;
for i:=0 to sessions do
begin
//在原有的客戶端連接數組中有中斷的客戶端連接
if not session[i].CUsed then
begin
session[i].CHandle := Socket.SocketHandle ;//客戶端套接字句柄
session[i].CSocket := Socket; //客戶端套接字
session[i].CName := Socket.RemoteHost ; //客戶端計算機名稱
session[i].CAddress := Socket.RemoteAddress ;//客戶端計算機IP
session[i].CUsed := True; //連接數組當前位置已經占用
Break;
end;
j:=i;
end;
if j=sessions then
begin
inc(sessions);
session[j].CHandle := Socket.SocketHandle ;
session[j].CSocket := Socket;
session[j].CName := Socket.RemoteHost ;
session[j].CAddress := Socket.RemoteAddress ;
session[j].CUsed := True;
end;
StatusBar.Panels[0].Text := 客戶端 +Socket.RemoteHost + 已經連接;
end;
//當客戶端斷開連接時
procedure TfrmServerMain.ServerSocketClientDisconnect(Sender: TObject;
Socket: TCustomWinSocket);
var
  i:integer;
  begin
    for i:=0 to sessions do
    begin
      if session[i].CHandle =Socket.SocketHandle then
      begin
        session[i].CHandle :=0;
        session[i].CUsed := False;
        Break;
      end;
    end;
    StatusBar.Panels[0].Text :=客戶端 +Socket.RemoteHost + 已經斷開;
  end;

//關閉窗口
procedure TfrmServerMain.tbCloseClick(Sender: TObject);
begin
  Close;
end;

procedure TfrmServerMain.FormCreate(Sender: TObject);
begin
  sessions := 0;
end;

procedure TfrmServerMain.FormClose(Sender: TObject;
var Action: TCloseAction);
begin
  ServerSocket.Close ;
end;

//當客戶端正在與服務器端連接時
procedure TfrmServerMain.ServerSocketGetSocket(Sender: TObject;
Socket: Integer; var ClientSocket: TServerClientWinSocket);
begin
    StatusBar.Panels[0].Text :=客戶端正在連接...;
end;

//客戶端發生錯誤
procedure TfrmServerMain.ServerSocketClientError(Sender: TObject;
Socket: TCustomWinSocket; ErrorEvent: TErrorEvent;
var ErrorCode: Integer);
begin
    StatusBar.Panels[0].Text :=客戶端+Socket.RemoteHost +發生錯誤！;
ErrorCode := 0;
end;

end.

客戶端源碼(uClientMain.pas)：

unit uClientMain;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
ScktComp, ComCtrls, ToolWin, ExtCtrls, StdCtrls, Buttons;

const
  SocketHost = 172.16.1.6; //服務器端地址

type
  TfrmClientMain = class(TForm)
  ControlBar1: TControlBar;
  ToolBar1: TToolBar;
  tbConnected: TToolButton;
  tbSend: TToolButton;
  tbClose: TToolButton;
  tbDisconnected: TToolButton;
  ClientSocket: TClientSocket;
  Edit1: TEdit;
  Memo1: TMemo;
  StatusBar: TStatusBar;
  btnSend: TBitBtn;
  procedure tbConnectedClick(Sender: TObject);
  procedure tbDisconnectedClick(Sender: TObject);
  procedure ClientSocketRead(Sender: TObject; Socket: TCustomWinSocket);
  procedure tbSendClick(Sender: TObject);
  procedure tbCloseClick(Sender: TObject);
  procedure FormShow(Sender: TObject);
  procedure ClientSocketConnect(Sender: TObject;
  Socket: TCustomWinSocket);
  procedure ClientSocketConnecting(Sender: TObject;
  Socket: TCustomWinSocket);
  procedure ClientSocketDisconnect(Sender: TObject;
  Socket: TCustomWinSocket);
  procedure FormClose(Sender: TObject; var Action: TCloseAction);
  procedure ClientSocketError(Sender: TObject; Socket: TCustomWinSocket;
  ErrorEvent: TErrorEvent; var ErrorCode: Integer);
  private
    { Private declarations }
  public
    { Public declarations }
end;

var
  frmClientMain: TfrmClientMain;

implementation
  {$R *.DFM}

//打開套接字連接
procedure TfrmClientMain.tbConnectedClick(Sender: TObject);
begin
  ClientSocket.Open ;
end;

//關閉套接字連接
procedure TfrmClientMain.tbDisconnectedClick(Sender: TObject);
begin
  ClientSocket.Close;
end;

//接受服務器端的回復
procedure TfrmClientMain.ClientSocketRead(Sender: TObject;
Socket: TCustomWinSocket);
begin
  Memo1.Lines.Add(Socket.ReceiveText);
end;

//發送信息到服務器端
procedure TfrmClientMain.tbSendClick(Sender: TObject);
begin
  ClientSocket.Socket.SendText(Edit1.Text); 
end;

procedure TfrmClientMain.tbCloseClick(Sender: TObject);
begin
  Close;
end;

//設置要連接的服務器端地址
procedure TfrmClientMain.FormShow(Sender: TObject);
begin
  ClientSocket.Host := SocketHost;
end;
//已經連接到服務器端
procedure TfrmClientMain.ClientSocketConnect(Sender: TObject;
Socket: TCustomWinSocket);
begin
  tbSend.Enabled := True;
  tbDisconnected.Enabled :=True;
  btnSend.Enabled := True;
  StatusBar.Panels[0].Text := 已經連接到 + Socket.RemoteHost ;
end;

//正在連接到服務器端
//(***本文出處：南山古桃(nsgtao)的百度空間：http://hi.baidu.com/nsgtao/ ****)
procedure TfrmClientMain.ClientSocketConnecting(Sender: TObject;
Socket: TCustomWinSocket);
begin
  StatusBar.Panels[0].Text := 正在連接到服務器... ;
end;
//當斷開與服務器端的連接時發生
procedure TfrmClientMain.ClientSocketDisconnect(Sender: TObject;
Socket: TCustomWinSocket);
begin
  tbSend.Enabled := False;
  btnSend.Enabled := False;
  tbDisconnected.Enabled := False;
  StatusBar.Panels[0].Text := 已經斷開與 + Socket.RemoteHost + 的連接;
end;

procedure TfrmClientMain.FormClose(Sender: TObject;
var Action: TCloseAction);
begin
  ClientSocket.Close ;
end;

//當與服務器端的連接發生錯誤時
procedure TfrmClientMain.ClientSocketError(Sender: TObject;
Socket: TCustomWinSocket; ErrorEvent: TErrorEvent;
var ErrorCode: Integer);
begin
  StatusBar.Panels[0].Text := 與服務器端的連接發生錯誤;
  ErrorCode := 0;
end;

end.