<br>用Delphi設計自己的代理服務器
<br>
<br> 筆者在編寫一個上網計費軟件時，涉及到如何對局域網中各工作站上網計費問題。一般來講，這些工作站通過代理服務器上網，而采用現成的代理服務器軟件時，由于代理服務器軟件是封閉的系統，很難編寫程序獲取實時的上網計時信息。因此，考慮是否能編寫自己的代理服務器，一方面解決群體上網，另一方面又解決上網的計費問題呢？
<br> 經過實驗性編程，終于圓滿地解決了該問題。現寫出來，與各位同行分享。
<br>
<br>1、思路
<br>當前流行的瀏覽器的系統選項中有一個參數，即“通過代理服務器連接”，經過編程測
<br>試，當局域網中一臺工作站指定了該屬性，再發出Internet請求時，請求數據將發送到所指定的代理服務器上，以下為請求數據包示例：
<br> GEThttp://home.microsoft.com/intl/cn/HTTP/1.0
<br> Accept:*/*
<br> Accept-Language:zh-cn
<br> Accept-Encoding:gzip,deflate
<br> User-Agent:Mozilla/4.0(compatible;MSIE5.0;WindowsNT)
<br> Host:home.microsoft.com
<br> Proxy-Connection:Keep-Alive
<br>其中第一行為目標URL及相關方法、協議，“Host”行指定了目標主機的地址。
<br>由此知道了代理服務的過程：接收被代理端的請求、連接真正的主機、接收主機返回的數據、將接收數據發送到被代理端。
<br>為此可編寫一個簡單的程序，完成上述網絡通信重定向問題。
<br>用Delphi設計時，選用ServerSocket作為與被代理工作站通信的套接字控件，選用ClientSocket動態數組作為與遠程主機通信的套接字控件。
<br>編程時應解決的一個重要問題是多重連接處理問題，為了加快代理服務的速度和被代理端的響應速度，套接字控件的屬性應設為非阻塞型；各通信會話與套接字動態綁定，用套接字的SocketHandle屬性值確定屬于哪一個會話。
<br>通信的銜接過程如下圖所示：
<br>
<br> 代理服務器
<br>
<br> Serversocket
<br> (1)接收
<br> 被代理端發送遠程主機
<br> (6)(2)(5)
<br> BrowserClientSocket(4)WebServer
<br> 接收
<br> 發送(3)
<br>
<br>
<br>（1）、被代理端瀏覽器發出Web請求，代理服務器的Serversocket接收到請求。
<br>（2）、代理服務器程序自動創建一個ClientSocket，并設置主機地址、端口等屬性，然后連接遠程主機。
<br>（3）、遠程連通后激發發送事件，將Serversocket接收到的Web請求數據包發送到遠程主機。
<br>（4）、當遠程主機返回頁面數據時，激發ClientSocket的讀事件，讀取頁面數據。
<br>（5）、代理服務器程序根據綁定信息確定屬于ServerSocket控件中的哪一個Socket應該將從主機接收的頁面信息發送到被代理端。
<br>（6）、ServerSocket中的對應Socket將頁面數據發送到被代理端。
<br>
<br>2、程序編寫
<br>使用Delphi設計以上通信過程非常簡單，主要是ServerSocket、ClientSocket的相關事
<br>件驅動程序的程序編寫。下面給出作者編寫的實驗用代理服務器界面與源程序清單，內含簡要功能說明：
<br>
<br>unitmain;
<br>
<br>interface
<br>
<br>uses
<br> Windows,Messages,SysUtils,Classes,Graphics,Controls,Forms,Dialogs,
<br> ExtCtrls,ScktComp,TrayIcon,Menus,StdCtrls;
<br>
<br>type
<br> session_record=record
<br> Used:boolean;
<br> SS_Handle:integer;
<br> CSocket:TClientSocket;
<br> Lookingup:boolean;
<br> LookupTime:integer;
<br> Request:boolean;
<br> request_str:string;
<br> client_connected:boolean;
<br> remote_connected:boolean;
<br>end;
<br>
<br>type
<br> TForm1=class(TForm)
<br> ServerSocket1:TServerSocket;
<br> ClientSocket1:TClientSocket;
<br> Timer2:TTimer;
<br> TrayIcon1:TTrayIcon;
<br> PopupMenu1:TPopupMenu;
<br> N11:TMenuItem;
<br> N21:TMenuItem;
<br> N1:TMenuItem;
<br> N01:TMenuItem;
<br> Memo1:TMemo;
<br> Edit1:TEdit;
<br> Label1:TLabel;
<br> Timer1:TTimer;
<br> procedureTimer2Timer(Sender:TObject);
<br> procedureN11Click(Sender:TObject);
<br> procedureFormCreate(Sender:TObject);
<br> procedureFormClose(Sender:TObject;varAction:TCloseAction);
<br> procedureN21Click(Sender:TObject);
<br> procedureN01Click(Sender:TObject);
<br> procedureServerSocket1ClientConnect(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br> procedureServerSocket1ClientDisconnect(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br> procedureServerSocket1ClientError(Sender:TObject;
<br> Socket:TCustomWinSocket;ErrorEvent:TErrorEvent;
<br> varErrorCode:Integer);
<br> procedureServerSocket1ClientRead(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br> procedureClientSocket1Connect(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br> procedureClientSocket1Disconnect(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br> procedureClientSocket1Error(Sender:TObject;Socket:TCustomWinSocket;
<br> ErrorEvent:TErrorEvent;varErrorCode:Integer);
<br> procedureClientSocket1Write(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br> procedureClientSocket1Read(Sender:TObject;Socket:TCustomWinSocket);
<br> procedureServerSocket1Listen(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br> procedureAppException(Sender:TObject;E:Exception);
<br> procedureTimer1Timer(Sender:TObject);
<br> **
<br> {**declarations}
<br> public
<br> Service_Enabled:boolean;
<br> session:arrayofsession_record;
<br> sessions:integer;
<br> LookUpTimeOut:integer;
<br> InvalidRequests:integer;
<br> end;
<br>
<br>var
<br> Form1:TForm1;
<br>
<br>implementation
<br>
<br>{$R*.DFM}
<br>
<br>file://系統啟動定時器，啟動窗顯示完成后，縮小到SystemTray…
<br>procedureTForm1.Timer2Timer(Sender:TObject);
<br>begin
<br> timer2.Enabled:=false;
<br> sessions:=0;
<br> Application.OnException:=AppException;
<br> invalidRequests:=0;
<br> LookUpTimeOut:=60000;
<br> timer1.Enabled:=true;
<br> n11.Enabled:=false;
<br> n21.Enabled:=true;
<br> serversocket1.Port:=988;
<br> serversocket1.Active:=true;
<br> form1.hide;{隱藏界面，縮小到SystemTray上}
<br>end;
<br>
<br>file://開啟服務菜單項…
<br>procedureTForm1.N11Click(Sender:TObject);
<br>begin
<br> serversocket1.Active:=true;
<br>end;
<br>
<br>
<br>file://停止服務菜單項…
<br>procedureTForm1.N21Click(Sender:TObject);
<br>begin
<br> serversocket1.Active:=false;
<br> N11.Enabled:=True;
<br> N21.Enabled:=False;
<br> Service_Enabled:=false;
<br>end;
<br>
<br>
<br>file://主窗口建立…
<br>procedureTForm1.FormCreate(Sender:TObject);
<br>begin
<br> Service_Enabled:=false;
<br> timer2.Enabled:=true;
<br>end;
<br>
<br>file://窗口關閉時…
<br>procedureTForm1.FormClose(Sender:TObject;varAction:TCloseAction);
<br>begin
<br> timer1.Enabled:=false;
<br> ifService_Enabledthen
<br> serversocket1.Active:=false;
<br>end;
<br>
<br>file://退出程序按鈕…
<br>procedureTForm1.N01Click(Sender:TObject);
<br>begin
<br> form1.Close;
<br>end;
<br>
<br>file://開啟代理服務后…
<br>procedureTForm1.ServerSocket1Listen(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br>begin
<br> Service_Enabled:=true;
<br> N11.Enabled:=false;
<br> N21.Enabled:=true;
<br>end;
<br>
<br>file://被代理端連接到代理服務器后，建立一個會話，并與套接字綁定…
<br>procedureTForm1.ServerSocket1ClientConnect(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br>var
<br>i,j:integer;
<br>begin
<br> j:=-1;
<br> fori:=1tosessionsdo
<br> ifnotsession[i-1].Usedandnotsession[i-1].CSocket.activethen
<br> begin
<br> j:=i-1;
<br> session[j].Used:=true;
<br> break;
<br> end
<br> else
<br> ifnotsession[i-1].Usedandsession[i-1].CSocket.activethen
<br> session[i-1].CSocket.active:=false;
<br> ifj=-1then
<br> begin
<br> j:=sessions;
<br> inc(sessions);
<br> setlength(session,sessions);
<br> session[j].Used:=true;
<br> session[j].CSocket:=TClientSocket.Create(nil);
<br> session[j].CSocket.OnConnect:=ClientSocket1Connect;
<br> session[j].CSocket.OnDisconnect:=ClientSocket1Disconnect;
<br> session[j].CSocket.OnError:=ClientSocket1Error;
<br> session[j].CSocket.OnRead:=ClientSocket1Read;
<br> session[j].CSocket.OnWrite:=ClientSocket1Write;
<br> session[j].Lookingup:=false;
<br> end;
<br> session[j].SS_Handle:=socket.socketHandle;
<br> session[j].Request:=false;
<br> session[j].client_connected:=true;
<br> session[j].remote_connected:=false;
<br> edit1.text:=inttostr(sessions);
<br>end;
<br>
<br>file://被代理端斷開時…
<br>procedureTForm1.ServerSocket1ClientDisconnect(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br>var
<br>i,j,k:integer;
<br>begin
<br> fori:=1tosessionsdo
<br> if(session[i-1].SS_Handle=socket.SocketHandle)andsession[i-1].Usedthen
<br> begin
<br> session[i-1].client_connected:=false;
<br> ifsession[i-1].remote_connectedthen
<br> session[i-1].CSocket.active:=false
<br> else
<br> session[i-1].Used:=false;
<br> break;
<br> end;
<br> j:=sessions;
<br> k:=0;
<br> fori:=1tojdo
<br> begin
<br> ifsession[j-i].Usedthen
<br> break;
<br> inc(k);
<br> end;
<br> ifk%26gt;0then
<br> begin
<br> sessions:=sessions-k;
<br> setlength(session,sessions);
<br> end;
<br> edit1.text:=inttostr(sessions);
<br>end;
<br>
<br>file://通信錯誤出現時…
<br>procedureTForm1.ServerSocket1ClientError(Sender:TObject;
<br> Socket:TCustomWinSocket;ErrorEvent:TErrorEvent;
<br> varErrorCode:Integer);
<br>var
<br>i,j,k:integer;
<br>begin
<br> fori:=1tosessionsdo
<br> if(session[i-1].SS_Handle=socket.SocketHandle)andsession[i-1].Usedthen
<br> begin
<br> session[i-1].client_connected:=false;
<br> ifsession[i-1].remote_connectedthen
<br> session[i-1].CSocket.active:=false
<br> else
<br> session[i-1].Used:=false;
<br> break;
<br> end;
<br> j:=sessions;
<br> k:=0;
<br> fori:=1tojdo
<br> begin
<br> ifsession[j-i].Usedthen
<br> break;
<br> inc(k);
<br> end;
<br> ifk%26gt;0then
<br> begin
<br> sessions:=sessions-k;
<br> setlength(session,sessions);
<br> end;
<br> edit1.text:=inttostr(sessions);
<br> errorcode:=0;
<br>end;
<br>
<br>file://被代理端發送來頁面請求時…
<br>procedureTForm1.ServerSocket1ClientRead(Sender:TObject;
<br> Socket:TCustomWinSocket);
<br>var
<br>tmp,line,host:string;
<br>i,j,port:integer;
<br>begin
<br> fori:=1tosessionsdo
<br> ifsession[i-1].Usedand(session[i-1].SS_Handle=socket.sockethandle)then
<br> begin
<br> session[i-1].request_str:=socket.ReceiveText;
<br> tmp:=session[i-1].request_str;
<br> memo1.lines.add(tmp);
<br> j:=pos(char(13)+char(10),tmp);
<br> whilej%26gt;0do
<br> begin
<br> line:=copy(tmp,1,j-1);
<br> delete(tmp,1,j+1);
<br> j:=pos('Host',line);
<br> ifj%26gt;0then
<br> begin
<br> delete(line,1,j+5);
<br> j:=pos(':',line);
<br> ifj%26gt;0then
<br> begin
<br> host:=copy(line,1,j-1);
<br> delete(line,1,j);
<br> try
<br> port:=strtoint(line);
<br> except
<br> port:=80;
<br> end;
<br> end
<br> else
<br> begin
<br> host:=trim(line);
<br> port:=80;
<br> end;
<br> ifnotsession[i-1].remote_connectedthen
<br> begin
<br> session[i-1].Request:=true;