筆者在編寫(xiě)一個(gè)上網(wǎng)計(jì)費(fèi)軟件時(shí),涉及到如何對(duì)局域網(wǎng)中各工作站上網(wǎng)計(jì)費(fèi)問(wèn)題。一般來(lái)講,這些工作站通過(guò)代理服務(wù)器上網(wǎng),而采用現(xiàn)成的代理服務(wù)器軟件時(shí),由于代理服務(wù)器軟件是封閉的系統(tǒng),很難編寫(xiě)程序獲取實(shí)時(shí)的上網(wǎng)計(jì)時(shí)信息。因此,考慮是否能編寫(xiě)自己的代理服務(wù)器,一方面解決群體上網(wǎng),另一方面又解決上網(wǎng)的計(jì)費(fèi)問(wèn)題呢? 經(jīng)過(guò)實(shí)驗(yàn)性編程,終于圓滿地解決了該問(wèn)題。現(xiàn)寫(xiě)出來(lái),與各位同行分享。
1、 思路 當(dāng)前流行的瀏覽器的系統(tǒng)選項(xiàng)中有一個(gè)參數(shù),即“通過(guò)代理服務(wù)器連接”,經(jīng)過(guò)編程測(cè) 試,當(dāng)局域網(wǎng)中一臺(tái)工作站指定了該屬性,再發(fā)出Internet請(qǐng)求時(shí),請(qǐng)求數(shù)據(jù)將發(fā)送到所指定的代理服務(wù)器上,以下為請(qǐng)求數(shù)據(jù)包示例: GET http://home.microsoft.com/intl/cn/ HTTP/1.0 Accept: */* Accept-Language: zh-cn Accept-Encoding: gzip, deflate User-Agent: Mozilla/4.0 (compatible; MSIE 5.0; Windows NT) Host: home.microsoft.com Proxy-Connection: Keep-Alive 其中第一行為目標(biāo)URL及相關(guān)方法、協(xié)議,“Host”行指定了目標(biāo)主機(jī)的地址。 由此知道了代理服務(wù)的過(guò)程:接收被代理端的請(qǐng)求、連接真正的主機(jī)、接收主機(jī)返回的數(shù)據(jù)、將接收數(shù)據(jù)發(fā)送到被代理端。 為此可編寫(xiě)一個(gè)簡(jiǎn)單的程序,完成上述網(wǎng)絡(luò)通信重定向問(wèn)題。 用Delphi設(shè)計(jì)時(shí),選用ServerSocket作為與被代理工作站通信的套接字控件,選用ClientSocket動(dòng)態(tài)數(shù)組作為與遠(yuǎn)程主機(jī)通信的套接字控件。 編程時(shí)應(yīng)解決的一個(gè)重要問(wèn)題是多重連接處理問(wèn)題,為了加快代理服務(wù)的速度和被代理端的響應(yīng)速度,套接字控件的屬性應(yīng)設(shè)為非阻塞型;各通信會(huì)話與套接字動(dòng)態(tài)綁定,用套接字的SocketHandle屬性值確定屬于哪一個(gè)會(huì)話。 通信的銜接過(guò)程如下圖所示:
代理服務(wù)器 Serversocket (1) 接 收 被代理端 發(fā) 送 遠(yuǎn)程主機(jī) (6) (2) (5) Browser ClientSocket (4) Web Server 接 收 發(fā) 送 (3)
(1)、被代理端瀏覽器發(fā)出Web請(qǐng)求,代理服務(wù)器的Serversocket接收到請(qǐng)求。 (2)、代理服務(wù)器程序自動(dòng)創(chuàng)建一個(gè)ClientSocket,并設(shè)置主機(jī)地址、端口等屬性,然后連接遠(yuǎn)程主機(jī)。 (3)、遠(yuǎn)程連通后激發(fā)發(fā)送事件,將Serversocket接收到的Web請(qǐng)求數(shù)據(jù)包發(fā)送到遠(yuǎn)程主機(jī)。 (4)、當(dāng)遠(yuǎn)程主機(jī)返回頁(yè)面數(shù)據(jù)時(shí),激發(fā)ClientSocket的讀事件,讀取頁(yè)面數(shù)據(jù)。 (5)、代理服務(wù)器程序根據(jù)綁定信息確定屬于ServerSocket控件中的哪一個(gè)Socket應(yīng)該將從主機(jī)接收的頁(yè)面信息發(fā)送到被代理端。 (6)、ServerSocket中的對(duì)應(yīng)Socket將頁(yè)面數(shù)據(jù)發(fā)送到被代理端。
2、 程序編寫(xiě) 使用Delphi設(shè)計(jì)以上通信過(guò)程非常簡(jiǎn)單,主要是ServerSocket、ClientSocket的相關(guān)事 件驅(qū)動(dòng)程序的程序編寫(xiě)。下面給出作者編寫(xiě)的實(shí)驗(yàn)用代理服務(wù)器界面與源程序清單,內(nèi)含簡(jiǎn)要功能說(shuō)明:
unit main;
interface
uses Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs, ExtCtrls, ScktComp, TrayIcon, Menus, StdCtrls;
type session_record=record Used: boolean; {會(huì)話記錄是否可用} SS_Handle: integer; {代理服務(wù)器套接字句柄} CSocket: TClientSocket; {用于連接遠(yuǎn)程的套接字} Lookingup: boolean; {是否正在查找服務(wù)器} LookupTime: integer; {查找服務(wù)器時(shí)間} Request: boolean; {是否有請(qǐng)求} request_str: string; {請(qǐng)求數(shù)據(jù)塊} client_connected: boolean; {客戶機(jī)聯(lián)機(jī)標(biāo)志} remote_connected: boolean; {遠(yuǎn)程服務(wù)器連接標(biāo)志} end;
type TForm1 = class(TForm) ServerSocket1: TServerSocket; ClientSocket1: TClientSocket; Timer2: TTimer; TrayIcon1: TTrayIcon; PopupMenu1: TPopupMenu; N11: TMenuItem; N21: TMenuItem; N1: TMenuItem; N01: TMenuItem; Memo1: TMemo; Edit1: TEdit; Label1: TLabel; Timer1: TTimer; procedure Timer2Timer(Sender: TObject); procedure N11Click(Sender: TObject); procedure FormCreate(Sender: TObject); procedure FormClose(Sender: TObject; var Action: TCloseAction); procedure N21Click(Sender: TObject); procedure N01Click(Sender: TObject); 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 ServerSocket1Listen(Sender: TObject; Socket: TCustomWinSocket); procedure AppException(Sender: TObject; E: Exception); procedure Timer1Timer(Sender: TObject); private { Private declarations } public Service_Enabled: boolean; {代理服務(wù)是否開(kāi)啟} session: array of session_record; {會(huì)話數(shù)組} sessions: integer; {會(huì)話數(shù)} LookUpTimeOut: integer; {連接超時(shí)值} InvalidRequests: integer; {無(wú)效請(qǐng)求數(shù)} end;
var Form1: TForm1;
implementation
{$R *.DFM}
file://系統(tǒng)啟動(dòng)定時(shí)器,啟動(dòng)窗顯示完成后,縮小到System Tray… procedure TForm1.Timer2Timer(Sender: TObject); begin timer2.Enabled:=false; {關(guān)閉定時(shí)器} sessions:=0; {會(huì)話數(shù)=0} Application.OnException := AppException; {為了屏蔽代理服務(wù)器出現(xiàn)的異常} invalidRequests:=0; {0錯(cuò)誤} LookUpTimeOut:=60000; {超時(shí)值=1分鐘} timer1.Enabled:=true; {打開(kāi)定時(shí)器} n11.Enabled:=false; {開(kāi)啟服務(wù)菜單項(xiàng)失效} n21.Enabled:=true; {關(guān)閉服務(wù)菜單項(xiàng)有效} serversocket1.Port:=988; {代理服務(wù)器端口=988} serversocket1.Active:=true; {開(kāi)啟服務(wù)} form1.hide; {隱藏界面,縮小到System Tray上} end;
file://開(kāi)啟服務(wù)菜單項(xiàng)… procedure TForm1.N11Click(Sender: TObject); begin serversocket1.Active:=true; {開(kāi)啟服務(wù)} end;
file://停止服務(wù)菜單項(xiàng)… procedure TForm1.N21Click(Sender: TObject); begin serversocket1.Active:=false; {停止服務(wù)} N11.Enabled:=True; N21.Enabled:=False; Service_Enabled:=false; {標(biāo)志清零} end;
file://主窗口建立… procedure TForm1.FormCreate(Sender: TObject); begin Service_Enabled:=false; timer2.Enabled:=true; {窗口建立時(shí),打開(kāi)定時(shí)器} end;
file://窗口關(guān)閉時(shí)… procedure TForm1.FormClose(Sender: TObject; var Action: TCloseAction); begin timer1.Enabled:=false; {關(guān)閉定時(shí)器} if Service_Enabled then serversocket1.Active:=false; {退出程序時(shí)關(guān)閉服務(wù)} end;
file://退出程序按鈕… procedure TForm1.N01Click(Sender: TObject); begin form1.Close; {退出程序} end;
file://開(kāi)啟代理服務(wù)后… procedure TForm1.ServerSocket1Listen(Sender: TObject; Socket: TCustomWinSocket); begin Service_Enabled:=true; {置正在服務(wù)標(biāo)志} N11.Enabled:=false; N21.Enabled:=true; end;
file://被代理端連接到代理服務(wù)器后,建立一個(gè)會(huì)話,并與套接字綁定… procedure TForm1.ServerSocket1ClientConnect(Sender: TObject; Socket: TCustomWinSocket); var i,j: integer; begin j:=-1; for i:=1 to sessions do {查找是否有空白項(xiàng)} if not session[i-1].Used and not session[i-1].CSocket.active then begin j:=i-1; {有,分配它} session[j].Used:=true; {置為在用} break; end else if not session[i-1].Used and session[i-1].CSocket.active then session[i-1].CSocket.active:=false; if j=-1 then begin {無(wú),新增一個(gè)} j:=sessions; inc(sessions); setlength(session,sessions); session[j].Used:=true; {置為在用} 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].Lookingup:=false; end; session[j].SS_Handle:=socket.socketHandle; {保存句柄,實(shí)現(xiàn)綁定} session[j].Request:=false; {無(wú)請(qǐng)求} session[j].client_connected:=true; {客戶機(jī)已連接} session[j].remote_connected:=false; {遠(yuǎn)程未連接} edit1.text:=inttostr(sessions); end;
file://被代理端斷開(kāi)時(shí)… 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; {客戶機(jī)未連接} if session[i-1].remote_connected then session[i-1].CSocket.active:=false {假如遠(yuǎn)程尚連接,斷開(kāi)它} else session[i-1].Used:=false; {假如兩者都斷開(kāi),則置釋放資源標(biāo)志} break; end; j:=sessions; k:=0; for i:=1 to j do {統(tǒng)計(jì)會(huì)話數(shù)組尾部有幾個(gè)未用項(xiàng)} begin if session[j-i].Used then break; inc(k); end; if k>0 then {修正會(huì)話數(shù)組,釋放尾部未用項(xiàng)} begin sessions:=sessions-k; setlength(session,sessions); end; edit1.text:=inttostr(sessions); end;
file://通信錯(cuò)誤出現(xiàn)時(shí)… procedure TForm1.ServerSocket1ClientError(Sender: TObject; Socket: TCustomWinSocket; ErrorEvent: TErrorEvent; var ErrorCode: Integer); 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; {客戶機(jī)未連接} if session[i-1].remote_connected then session[i-1].CSocket.active:=false {假如遠(yuǎn)程尚連接,斷開(kāi)它} else session[i-1].Used:=false; {假如兩者都斷開(kāi),則置釋放資源標(biāo)志} 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); errorcode:=0; end;
file://被代理端發(fā)送來(lái)頁(yè)面請(qǐng)求時(shí)… procedure TForm1.ServerSocket1ClientRead(Sender: TObject; Socket: TCustomWinSocket); var tmp,line,host: string; i,j,port: integer; begin for i:=1 to sessions do {判斷是哪一個(gè)會(huì)話} if session[i-1].Used and (session[i-1].SS_Handle=socket.sockethandle) then begin session[i-1].request_str:=socket.ReceiveText; {保存請(qǐng)求數(shù)據(jù)} tmp:=session[i-1].request_str; {存放到臨時(shí)變量} memo1.lines.add(tmp); j:=pos(char(13)+char(10),tmp); {一行標(biāo)志} while j>0 do {逐行掃描請(qǐng)求文本,查找主機(jī)地址} begin line:=copy(tmp,1,j-1); {取一行} delete(tmp,1,j+1); {刪除一行} j:=pos('Host',line); {主機(jī)地址標(biāo)志} if j>0 then begin delete(line,1,j+5); {刪除前面的無(wú)效字符} j:=pos(':',line); if j>0 then begin host:=copy(line,1,j-1); delete(line,1,j); try port:=strtoint(line); except port:=80; end; end else begin host:=trim(line); {獲取主機(jī)地址} port:=80; end; if not session[i-1].remote_connected then {假如遠(yuǎn)征尚未連接} begin session[i-1].Request:=true; {置請(qǐng)求數(shù)據(jù)就緒標(biāo)志} session[i-1].CSocket.host:=host; {設(shè)置遠(yuǎn)程主機(jī)地址} session[i-1].CSocket.port:=port; {設(shè)置端口} session[i-1].CSocket.active:=true; {連接遠(yuǎn)程主機(jī)} session[i-1].Lookingup:=true; {置標(biāo)志} session[i-1].LookupTime:=0; {從0開(kāi)始計(jì)時(shí)} end else {假如遠(yuǎn)程已連接,直接發(fā)送請(qǐng)求} session[i-1].CSocket.socket.sendtext(session[i-1].request_str); break; {停止掃描請(qǐng)求文本} end; j:=pos(char(13)+char(10),tmp); {指向下一行} end; break; {停止循環(huán)} end; end;
file://當(dāng)連接遠(yuǎn)程主機(jī)成功時(shí)… 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; {置遠(yuǎn)程主機(jī)已連通標(biāo)志} session[i-1].Lookingup:=false; {清標(biāo)志} break; end; end;
file://當(dāng)遠(yuǎn)程主機(jī)斷開(kāi)時(shí)… procedure TForm1.ClientSocket1Disconnect(Sender: TObject; Socket: TCustomWinSocket); var i,j,k: integer; begin for i:=1 to sessions do if (session[i-1].CSocket.tag=socket.SocketHandle) and session[i-1].Used then begin session[i-1].remote_connected:=false; {置為未連接} if not session[i-1].client_connected then session[i-1].Used:=false {假如客戶機(jī)已斷開(kāi),則置釋放資源標(biāo)志} else for k:=1 to serversocket1.Socket.ActiveConnections do if (serversocket1.Socket.Connections[k-1].SocketHandle=session[i-1].SS_Handle) and session[i-1].used then begin serversocket1.Socket.Connections[k-1].Close; break; end; 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 {修正會(huì)話數(shù)組} begin sessions:=sessions-k; setlength(session,sessions); end; edit1.text:=inttostr(sessions); end;
file://當(dāng)與遠(yuǎn)程主機(jī)通信發(fā)生錯(cuò)誤時(shí)… procedure TForm1.ClientSocket1Error(Sender: TObject; Socket: TCustomWinSocket; ErrorEvent: TErrorEvent; var ErrorCode: Integer); var i,j,k: integer; begin for i:=1 to sessions do if (session[i-1].CSocket.tag=socket.SocketHandle) and session[i-1].Used then begin socket.close; session[i-1].remote_connected:=false; {置為未連接} if not session[i-1].client_connected then session[i-1].Used:=false {假如客戶機(jī)已斷開(kāi),則置釋放資源標(biāo)志} else for k:=1 to serversocket1.Socket.ActiveConnections do if (serversocket1.Socket.Connections[k-1].SocketHandle=session[i-1].SS_Handle) and session[i-1].used then begin serversocket1.Socket.Connections[k-1].Close; break; end; break; end; j:=sessions; k:=0; for i:=1 to j do begin if session[j-i].Used then break; inc(k); end; errorcode:=0; if k>0 then {修正會(huì)話數(shù)組} begin sessions:=sessions-k; setlength(session,sessions); end; edit1.text:=inttostr(sessions); end;
file://向遠(yuǎn)程主機(jī)發(fā)送頁(yè)面請(qǐng)求… procedure TForm1.ClientSocket1Write(Sender: TObject; Socket: TCustomWinSocket); var i: integer; begin for i:=1 to sessions do if (session[i-1].CSocket.tag=socket.SocketHandle) and session[i-1].Used then begin if session[i-1].Request then begin socket.SendText(session[i-1].request_str); {假如有請(qǐng)求,發(fā)送} session[i-1].Request:=false; {清標(biāo)志} end; break; end; end;
file://遠(yuǎn)程主機(jī)發(fā)來(lái)頁(yè)面數(shù)據(jù)時(shí)… procedure TForm1.ClientSocket1Read(Sender: TObject; Socket: TCustomWinSocket); var i,j: integer; rec_bytes: integer; {傳回的數(shù)據(jù)塊長(zhǎng)度} rec_Buffer: array[0..2047] of char; {傳回的數(shù)據(jù)塊緩沖區(qū)} begin for i:=1 to sessions do if (session[i-1].CSocket.tag=socket.SocketHandle) and session[i-1].Used then begin rec_bytes:=socket.ReceiveBuf(rec_buffer,2048); {接收數(shù)據(jù)} for j:=1 to serversocket1.Socket.ActiveConnections do if serversocket1.Socket.Connections[j-1].SocketHandle=session[i-1].SS_Handle then begin serversocket1.Socket.Connections[j-1].SendBuf(rec_buffer,rec_bytes); {發(fā)送數(shù)據(jù)} break; end; break; end; end;
file://“頁(yè)面找不到”等錯(cuò)誤信息出現(xiàn)時(shí)… procedure TForm1.AppException(Sender: TObject; E: Exception); begin inc(invalidrequests); end;
file://查找遠(yuǎn)程主機(jī)定時(shí)… procedure TForm1.Timer1Timer(Sender: TObject); var i,j: integer; begin for i:=1 to sessions do if session[i-1].Used and session[i-1].Lookingup then {假如正在連接} begin inc(session[i-1].LookupTime); if session[i-1].LookupTime>lookuptimeout then {假如超時(shí)} begin session[i-1].Lookingup:=false; session[i-1].CSocket.active:=false; {停止查找} for j:=1 to serversocket1.Socket.ActiveConnections do if serversocket1.Socket.Connections[j-1].SocketHandle=session[i-1].SS_Handle then begin serversocket1.Socket.Connections[j-1].Close; {斷開(kāi)客戶機(jī)} break; end; end; end; end; end.
3、 后記 由于這種設(shè)計(jì)思路僅僅在被代理端和遠(yuǎn)程主機(jī)之間增加了一個(gè)重定向功能,被代理端原 有的緩存技術(shù)等特點(diǎn)均保留,因此效率較高。經(jīng)過(guò)測(cè)試,利用1個(gè)33.6K的Modem上網(wǎng)時(shí),三到十個(gè)被代理工作站同時(shí)上網(wǎng),仍有較好的響應(yīng)速度。由于被代理工作站和代理服務(wù)器工作站之間的連接一般通過(guò)高速鏈路,因此瓶頸主要出現(xiàn)在代理服務(wù)器的上網(wǎng)方式上。 通過(guò)上述方法,作者成功開(kāi)發(fā)了一套完善的代理服務(wù)器軟件并與機(jī)房計(jì)費(fèi)系統(tǒng)完全集 成,實(shí)現(xiàn)了利用一臺(tái)工作站完成上網(wǎng)代理、上網(wǎng)計(jì)費(fèi)、用機(jī)計(jì)費(fèi)等功能。 有編程經(jīng)驗(yàn)的朋友完全可以另行增加代理服務(wù)器功能,如設(shè)定禁止訪問(wèn)站點(diǎn)、統(tǒng)計(jì)客戶流量、Web訪問(wèn)列表等等。
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