ClientSocket组件为客户端组件。它是通信的请求方，也就是说，它是主动地与服务器端建立连接。

ServerSocket组件为服务器端组件。它是通信的响应方，也就是说，它的动作是监听以及被动接受客户端的连接请求，并对请求进行回复。

【以下内容转自http://blog.csdn.net/dainiao01/article/details/2694257】
本例包括一个服务器端程序和一个客户端程序。客户端程序可以放到多个计算机上运行，同时与服务器端进行连接
通信。

本例的重点，一是演示客户端与服务器端如何通信；二是当有多个客户端同时连接到服务器端时，服务器端如何识
别每个客户端，并对请求给出相应的回复。为了保证一个客户端断开连接时不影响其它客户端与服务器端的通信，
同时保证服务器端能够正确回复客户端的请求，在本例中声明了一个记录类型：

服务器端源码（uServerMain.pas）：

unit uServerMain;

interface

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

const
CMax=10; //客户端最大连接数

type
client_record=record
CHandle: integer; //客户端套接字句柄
CSocket:TCustomWinSocket; //客户端套接字
CName:string; //客户端计算机名称
CAddress:string; //客户端计算机IP地址
CUsed: boolean; //客户端联机标志

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; //客户端连接数组
    Sessions: integer; //客户端连接数
end;

var
  frmServerMain: TfrmServerMain;

implementation
{$R *.DFM}

//打开套接字连接，并使套接字进入监听状态
procedure TfrmServerMain.tbConnectClick(Sender: TObject);
begin
  ServerSocket.Open ;
end;

//关闭套接字连接，不再监听客户端的请求
procedure TfrmServerMain.tbDisconnectedClick(Sender: TObject);
begin
  ServerSocket.Close;
  StatusBar.Panels[0].Text :=服务器套接字连接已经关闭，无法接受客户端的连接请求.;
end;

//从客户端读取信息
procedure TfrmServerMain.ServerSocketClientRead(Sender: TObject; 
 Socket: TCustomWinSocket);
var
  i:integer;
begin
  //将从客户端读取的信息添加到Memo1中
  Memo1.Lines.Add(Socket.ReceiveText);
  for i:=0 to sessions do
  begin
    //取得匹配的客户端
    if session[i].CHandle = Socket.SocketHandle then
    begin
      session[i].CSocket.SendText(回复客户端+session[i].CAddress+ ==> +Edit1.Text);
    end;
  end;
end;

//服务器端套接字进入监听状态，以便监听客户端的连接
procedure TfrmServerMain.ServerSocketListen(Sender: TObject;
Socket: TCustomWinSocket);
begin
    StatusBar.Panels[0].Text :=等待客户端连接...;
end;
//当客户端连接到服务器端以后
procedure TfrmServerMain.ServerSocketClientConnect(Sender: TObject;
Socket: TCustomWinSocket);
var
i,j:integer;
begin
j:=-1;
for i:=0 to sessions do
begin
//在原有的客户端连接数组中有中断的客户端连接
if not session[i].CUsed then
begin
session[i].CHandle := Socket.SocketHandle ;//客户端套接字句柄
session[i].CSocket := Socket; //客户端套接字
session[i].CName := Socket.RemoteHost ; //客户端计算机名称
session[i].CAddress := Socket.RemoteAddress ;//客户端计算机IP
session[i].CUsed := True; //连接数组当前位置已经占用
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 := 客户端 +Socket.RemoteHost + 已经连接;
end;
//当客户端断开连接时
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 :=客户端 +Socket.RemoteHost + 已经断开;
  end;

//关闭窗口
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;

//当客户端正在与服务器端连接时
procedure TfrmServerMain.ServerSocketGetSocket(Sender: TObject;
Socket: Integer; var ClientSocket: TServerClientWinSocket);
begin
    StatusBar.Panels[0].Text :=客户端正在连接...;
end;

//客户端发生错误
procedure TfrmServerMain.ServerSocketClientError(Sender: TObject;
Socket: TCustomWinSocket; ErrorEvent: TErrorEvent;
var ErrorCode: Integer);
begin
    StatusBar.Panels[0].Text :=客户端+Socket.RemoteHost +发生错误！;
ErrorCode := 0;
end;

end.

客户端源码(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; //服务器端地址

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}

//打开套接字连接
procedure TfrmClientMain.tbConnectedClick(Sender: TObject);
begin
  ClientSocket.Open ;
end;

//关闭套接字连接
procedure TfrmClientMain.tbDisconnectedClick(Sender: TObject);
begin
  ClientSocket.Close;
end;

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

//发送信息到服务器端
procedure TfrmClientMain.tbSendClick(Sender: TObject);
begin
  ClientSocket.Socket.SendText(Edit1.Text); 
end;

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

//设置要连接的服务器端地址
procedure TfrmClientMain.FormShow(Sender: TObject);
begin
  ClientSocket.Host := SocketHost;
end;
//已经连接到服务器端
procedure TfrmClientMain.ClientSocketConnect(Sender: TObject;
Socket: TCustomWinSocket);
begin
  tbSend.Enabled := True;
  tbDisconnected.Enabled :=True;
  btnSend.Enabled := True;
  StatusBar.Panels[0].Text := 已经连接到 + Socket.RemoteHost ;
end;

//正在连接到服务器端
//(***本文出处：南山古桃(nsgtao)的百度空间：http://hi.baidu.com/nsgtao/ ****)
procedure TfrmClientMain.ClientSocketConnecting(Sender: TObject;
Socket: TCustomWinSocket);
begin
  StatusBar.Panels[0].Text := 正在连接到服务器... ;
end;
//当断开与服务器端的连接时发生
procedure TfrmClientMain.ClientSocketDisconnect(Sender: TObject;
Socket: TCustomWinSocket);
begin
  tbSend.Enabled := False;
  btnSend.Enabled := False;
  tbDisconnected.Enabled := False;
  StatusBar.Panels[0].Text := 已经断开与 + Socket.RemoteHost + 的连接;
end;

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

//当与服务器端的连接发生错误时
procedure TfrmClientMain.ClientSocketError(Sender: TObject;
Socket: TCustomWinSocket; ErrorEvent: TErrorEvent;
var ErrorCode: Integer);
begin
  StatusBar.Panels[0].Text := 与服务器端的连接发生错误;
  ErrorCode := 0;
end;

end.