<br>用Delphi设计自己的代理服务器
<br>
<br> 笔者在编写一个上网计费软件时，涉及到如何对局域网中各工作站上网计费问题。一般来讲，这些工作站通过代理服务器上网，而采用现成的代理服务器软件时，由于代理服务器软件是封闭的系统，很难编写程序获取实时的上网计时信息。因此，考虑是否能编写自己的代理服务器，一方面解决群体上网，另一方面又解决上网的计费问题呢？
<br> 经过实验性编程，终于圆满地解决了该问题。现写出来，与各位同行分享。
<br>
<br>1、思路
<br>当前流行的浏览器的系统选项中有一个参数，即“通过代理服务器连接”，经过编程测
<br>试，当局域网中一台工作站指定了该属性，再发出Internet请求时，请求数据将发送到所指定的代理服务器上，以下为请求数据包示例：
<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>其中第一行为目标URL及相关方法、协议，“Host”行指定了目标主机的地址。
<br>由此知道了代理服务的过程：接收被代理端的请求、连接真正的主机、接收主机返回的数据、将接收数据发送到被代理端。
<br>为此可编写一个简单的程序，完成上述网络通信重定向问题。
<br>用Delphi设计时，选用ServerSocket作为与被代理工作站通信的套接字控件，选用ClientSocket动态数组作为与远程主机通信的套接字控件。
<br>编程时应解决的一个重要问题是多重连接处理问题，为了加快代理服务的速度和被代理端的响应速度，套接字控件的属性应设为非阻塞型；各通信会话与套接字动态绑定，用套接字的SocketHandle属性值确定属于哪一个会话。
<br>通信的衔接过程如下图所示：
<br>
<br> 代理服务器
<br>
<br> Serversocket
<br> (1)接收
<br> 被代理端发送远程主机
<br> (6)(2)(5)
<br> BrowserClientSocket(4)WebServer
<br> 接收
<br> 发送(3)
<br>
<br>
<br>（1）、被代理端浏览器发出Web请求，代理服务器的Serversocket接收到请求。
<br>（2）、代理服务器程序自动创建一个ClientSocket，并设置主机地址、端口等属性，然后连接远程主机。
<br>（3）、远程连通后激发发送事件，将Serversocket接收到的Web请求数据包发送到远程主机。
<br>（4）、当远程主机返回页面数据时，激发ClientSocket的读事件，读取页面数据。
<br>（5）、代理服务器程序根据绑定信息确定属于ServerSocket控件中的哪一个Socket应该将从主机接收的页面信息发送到被代理端。
<br>（6）、ServerSocket中的对应Socket将页面数据发送到被代理端。
<br>
<br>2、程序编写
<br>使用Delphi设计以上通信过程非常简单，主要是ServerSocket、ClientSocket的相关事
<br>件驱动程序的程序编写。下面给出作者编写的实验用代理服务器界面与源程序清单，内含简要功能说明：
<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://系统启动定时器，启动窗显示完成后，缩小到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;{隐藏界面，缩小到SystemTray上}
<br>end;
<br>
<br>file://开启服务菜单项…
<br>procedureTForm1.N11Click(Sender:TObject);
<br>begin
<br> serversocket1.Active:=true;
<br>end;
<br>
<br>
<br>file://停止服务菜单项…
<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://窗口关闭时…
<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://退出程序按钮…
<br>procedureTForm1.N01Click(Sender:TObject);
<br>begin
<br> form1.Close;
<br>end;
<br>
<br>file://开启代理服务后…
<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://被代理端连接到代理服务器后，建立一个会话，并与套接字绑定…
<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://被代理端断开时…
<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://通信错误出现时…
<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://被代理端发送来页面请求时…
<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;