为什么要Tclientsocket????

[sailorsky]

这是一个关于ｗｗｗ代理的源程序，

为什么也需要Tclientsocket?他的原理是什么？

请教高手》

部分程序如下：

unit main;

interface

uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls, ExtCtrls, ScktComp;
type
session_record=record
Used:boolean;
SS_Handle:integer;
CSocket:Tclientsocket;
Lookingup:boolean;
LookupTime:integer;
Request:boolean;
request_str:string;
client_connected:boolean;
remote_connected:boolean;
end;
type
TForm1 = class(TForm)
ServerSocket1: TServerSocket;
ClientSocket1: TClientSocket;
Timer1: TTimer;
Label1: TLabel;
Edit1: TEdit;
Memo1: TMemo;
btopen: TButton;
btclose: TButton;
Button3: TButton;
bthide: TButton;
Button1: TButton;
procedure AppException(sender:TObject;e:Exception);
procedure menuopenClick(Sender: TObject);
procedure menucloseClick(Sender: TObject);
procedure menuexit(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
procedure ServerSocket1Listen(Sender: TObject;
Socket: TCustomWinSocket);
procedure ServerSocket1ClientConnect(Sender: TObject;
Socket: TCustomWinSocket);
procedure ServerSocket1ClientDisconnect(Sender: TObject;
Socket: TCustomWinSocket);
procedure ServerSocket1ClientError(Sender: TObject;
Socket: TCustomWinSocket; ErrorEvent: TErrorEvent;
var ErrorCode: Integer);
procedure ServerSocket1ClientRead(Sender: TObject;
Socket: TCustomWinSocket);
procedure ClientSocket1Connect(Sender: TObject;
Socket: TCustomWinSocket);
procedure ClientSocket1Disconnect(Sender: TObject;
Socket: TCustomWinSocket);
procedure ClientSocket1Error(Sender: TObject; Socket: TCustomWinSocket;
ErrorEvent: TErrorEvent; var ErrorCode: Integer);
procedure ClientSocket1Write(Sender: TObject;
Socket: TCustomWinSocket);
procedure ClientSocket1Read(Sender: TObject; Socket: TCustomWinSocket);
procedure Timer1Timer(Sender: TObject);
procedure N4Click(Sender: TObject);
procedure ClientSocket1Lookup(Sender: TObject;
Socket: TCustomWinSocket);
procedure bthideClick(Sender: TObject);
procedure menuhideClick(Sender: TObject);
procedure Timer2Timer(Sender: TObject);
procedure Button1Click(Sender: TObject);
procedure ClientSocket1Connecting(Sender: TObject;
Socket: TCustomWinSocket);
private
{ Private declarations }
public
Server_Enabled:boolean;
session:array of session_record;
sessions:integer;
LookupTimeOut:integer;
InvalidRequests:integer;
end;

var
Form1: TForm1;

implementation

{$R *.DFM}
procedure TForm1.AppException (sender:TObject;E:Exception);
begin
//
end;
procedure TForm1.menuopenClick(Sender: TObject);
begin
serversocket1.active:=true;
end;

procedure TForm1.menucloseClick(Sender: TObject);
begin
serversocket1.Active :=false;
server_enabled:=false;
btopen.Enabled :=true;
btclose.Enabled :=false;
end;

procedure TForm1.menuexit(Sender: TObject);
begin
application.Terminate ;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
server_enabled:=false;
sessions:=0;
invalidrequests:=0;
LookupTimeOut:=60000;
timer1.Enabled :=true;
btopen.Enabled :=false;
btclose.Enabled :=true;
serversocket1.Port :=988;
serversocket1.Active :=true;
//application.OnActionExecute :=appexception;

end;

procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction);
begin
timer1.Enabled :=false;
if server_enabled then serversocket1.Active:=false;
end;

procedure TForm1.ServerSocket1Listen(Sender: TObject;
Socket: TCustomWinSocket);
begin
server_enabled:=true;
btopen.Enabled :=false;
btclose.Enabled :=true;
end;

procedure TForm1.ServerSocket1ClientConnect(Sender: TObject;
Socket: TCustomWinSocket);
var i,j:integer;
begin
j:=-1;
for i:=1 to sessions do
if not session[i-1].Used and not session[i-1].CSocket.active then
begin
j:=i-1;
session[j].Used :=true;
break;
end
else
if not session[i-1].Used and session[i-1].CSocket.active then session[j].CSocket .active:=false ;
if j=-1 then
begin
j:=sessions;
inc(sessions);
setlength(session,sessions);
session[j].Used :=true;
session[j].CSocket :=Tclientsocket.Create (nil);
session[j].CSocket.onconnect:=clientsocket1connect;
session[j].CSocket.ondisconnect:=clientsocket1disconnect;
session[j].CSocket.onerror:=clientsocket1error;
session[j].CSocket.onread:=clientsocket1read;
session[j].CSocket .onwrite:=clientsocket1write;
session[j].CSocket .onlookup:=clientsocket1lookup;
session[j].CSocket .onconnecting:=clientsocket1connecting;
session[j].lookingup:=false;
end;
session[j].SS_Handle :=socket.SocketHandle ;
session[j].Request :=false;
session[j].client_connected :=true;
session[j].remote_connected :=false;
edit1.Text :=inttostr(sessions);
end;

procedure TForm1.ServerSocket1ClientDisconnect(Sender: TObject;
Socket: TCustomWinSocket);
var i,j,k:integer;
begin
for i:=1 to sessions do
if (session[i-1].SS_Handle =socket.sockethandle) and session[i-1].Used then
begin
session[i-1].client_connected :=false;
if session[i-1].remote_connected then
session[i-1].CSocket.active:=false
else
session[i-1].Used :=false;
break;
end;
j:=sessions;
k:=0;
for i:=1 to j do
begin
if session[j-i].Used then break;
inc(k);
end;
if k>0 then
begin
sessions:=sessions-k;
setlength(session,sessions);
end;
edit1.Text :=inttostr(sessions);
end;
procedure TForm1.ClientSocket1Connect(Sender: TObject;
Socket: TCustomWinSocket);
var i:integer;
begin
for i:=1 to sessions do
if (session[i-1].Csocket.socket.sockethandle=socket.SocketHandle) and session[i-1].Used then
begin
session[i-1].CSocket.tag:=socket.sockethandle;
session[i-1].remote_connected :=true;
session[i-1].Lookingup :=false;
break;
end;
end;

[swexplorer]

据我对代理服务器的理解（如果这个程序本身就是代理服务器）：
IE <--> ServerSocket -- ClientSocket <--> 外部网站。

[swexplorer]

代理是一进一出，当然需要client和server两部分。