計算機網(wǎng)絡課程設計-利用VB實現(xiàn)FTP協(xié)議的基本功能.doc

課程設計任務書專業(yè)：計算機科學與技術(shù) 學號：學生姓名（簽名）： 設計題目：vb實現(xiàn)ftp協(xié)議的基本功能一、設計實驗條件 綜合摟實驗室二、設計任務及要求1. ftp協(xié)議可以使本地或遠程的客戶和服務器之間通過tcp傳輸協(xié)議進行文件傳輸；2. 要求利用vb實現(xiàn)ftp協(xié)議的基本功能。3. 用winsock控件來實現(xiàn)與ftp服務器端建立連接，該程序?qū)崿F(xiàn)下述命令功能：get:取遠方的一個文件put:傳給遠方一個文件pwd:顯示服務器當前目錄dir:列出服務器當前目錄cd:改變遠方當前目錄quit:退出返回4. 用serv-u搭建ftp服務器，設置客戶端訪問的用戶名、密碼、可以訪問的服務器目錄，對服務器可訪問目錄文件的操作權(quán)限（可讀、可寫）。三、設計報告的內(nèi)容1. 設計題目與設計任務（設計任務書）設計題目：實現(xiàn)ftp協(xié)議的基本功能，實現(xiàn)客戶機和服務器之間文件的上傳、下載、修改、重名名等設計任務：使用winsock控件，通過tcp協(xié)議與ftp服務器端建立連接。使用的環(huán)境是microsoft visual basic 6.0 中文版，ftp服務器搭建是基于serv-u軟件建立的服務器。2. 前言（緒論）(設計的目的、意義等)文件傳輸協(xié)議ftp（file transfer protocol）是在tcp/ip網(wǎng)絡中傳輸文件的一種格式規(guī)范，其目標是保證主機之間可靠和高效的傳輸程序或數(shù)據(jù)，向用戶屏蔽不同主機中各種文件存儲系統(tǒng)的細節(jié)。其規(guī)定在用戶和服務器之間建立兩個并行的tcp連接：控制連接和數(shù)據(jù)連接。前者是建立在用戶協(xié)議解釋器和服務器協(xié)議解釋器之間用于交換命令與響應的通信鏈路；后者是傳輸數(shù)據(jù)的全雙工連接。數(shù)據(jù)連接要先將文件拆分成分組再進行傳送，這樣做的目的是為了更加好的適應網(wǎng)絡中的帶寬限制，以及減少傳送期間節(jié)點的延時，以達到高速傳送。文件傳送是各種計算機網(wǎng)絡都實現(xiàn)的基本功能，文件傳送協(xié)議是一種最基本的應用層協(xié)議按照客戶/服務器的模式進行工作，提供交互式的訪問，是internet使用最廣泛的協(xié)議之一。本設計是用vb語言簡單實現(xiàn)文件傳輸協(xié)議，主要利用winsock控件，當中實現(xiàn)了上傳、下載、獲取服務器目錄等基本文件傳輸功能。 客戶端服務器數(shù)據(jù)傳輸控制字傳輸3. 設計主體（各部分設計內(nèi)容、分析、結(jié)論等）（1）建立基本的工程和窗口 實現(xiàn)“系統(tǒng)信息”功能。通過查詢注冊表來獲取一些相關(guān)的信息，導入要用到的訪問注冊版的api， 通過填寫服務器地址，用戶名和用戶密碼來實現(xiàn)與服務器的連接?？梢阅涿L問也可以填寫用戶名訪問。 下圖：設計主窗口的菜單和其他一些必需的控件。如：工具欄、左邊的treeview控件、添加右邊的listview控件等。 服務器配置：設置用戶有關(guān)信息 （2）基本類模塊：用于處理相關(guān)鏈接、上傳、下載等操作 1實現(xiàn)ftp文件類，即把有關(guān)的信息封裝成一個類，實現(xiàn)面向?qū)ο蟮乃枷?，便于管理private mvarfilename as string private mvarlastwritetime as date private mvarfilesize as long private mvarisdirectory as booleanprivate mvarfilepath as stringpublic property let isdirectory(byval vdata as boolean) mvarisdirectory = vdataend propertypublic property get isdirectory() as boolean isdirectory = mvarisdirectoryend propertypublic property let filesize(byval vdata as long) mvarfilesize = vdataend propertypublic property get filesize() as long filesize = mvarfilesizeend propertypublic property let lastwritetime(byval vdata as date) mvarlastwritetime = vdataend propertypublic property get lastwritetime() as date lastwritetime = mvarlastwritetimeend propertypublic property let filename(byval vdata as string) mvarfilename = vdataend propertypublic property get filename() as string filename = mvarfilenameend propertypublic property let filepath(byval vdata as string) mvarfilepath = vdataend propertypublic property get filepath() as string filepath = mvarfilepathend property 2實現(xiàn)ftp連接類。定義兩個winsock控件變量，一個用戶控制連接，一個用于數(shù)據(jù)連接*winsock control for control connectionprivate withevents wsccontrol as mswinsocklib.winsockwinsock control for data connectionprivate withevents wscdata as mswinsocklib.winsock*為wsccontrol添加dataarrival事件響應方法。通過調(diào)用getdata方法獲取到達的數(shù)據(jù)，并加在原來的數(shù)據(jù)的后面，如果相應碼是426，表示與服務器的連接關(guān)閉，重置類變量，并關(guān)閉wsccontrol。private sub wsccontrol_dataarrival(byval bytestotal as long) dim strdata as string wsccontrol.getdata strdata m_strwinsockbuffer = m_strwinsockbuffer & strdata m_strlastserverresponse = strdata m_objtimeout.reset if getresponsecode(strdata) = 426 then if m_btransferinprogress or m_buploadfile then wscdata.close close m_intlocalfileid m_strdatabuffer = m_ldownloadedbytes = 0 m_luploadedbytes = 0 m_btransferinprogress = false m_buploadfile = false m_bfileisopened = false end if wsccontrol.close m_bbusy = false end if debug.print left(strdata, len(strdata) - 2)end sub處理與ftp服務器的連接。用的ftp服務器需要用戶名和密碼進行帳戶認證，需要先處理user命令和pass命令，獲取用戶名，附加到user命令中發(fā)送到服務器。并處理服務器的響應，最后返回ftp相應碼，標識登錄是否成功。private function processusercommand() as ftp_response_codes dim strdata as string on error goto processusercommand_err_handler raiseevent statechanged(ftp_connection_authentication) m_strusername = iif(len(m_strusername) 0, m_strusername, anonymous) if len(m_strpassword) = 0 then if m_strusername = anonymous then m_strpassword = else raise error exit function end if end if wsccontrol.senddata user & m_strusername & vbcrlf debug.print user & m_strusername m_objtimeout.starttimer do doevents if m_objtimeout.timeout then m_lasterror = error_ftp_user_timeout exit do end if if len(m_strwinsockbuffer) response_code_lenght then strdata = m_strwinsockbuffer m_strwinsockbuffer = exit do end if loop m_objtimeout.stoptimer select case getresponsecode(strdata) case ftp_response_user_logged_in processusercommand = ftp_response_user_logged_in case ftp_response_user_name_ok_need_password processusercommand = ftp_response_user_name_ok_need_password case else processftpresponse getresponsecode(strdata) end select exit_label: exit functionprocessusercommand_err_handler: if not processwinsockerror(err.number, err.description) then err.raise vbobjecterror + 1000 + err.number, cftpconnection.processusercommand, err.description end if goto exit_label end functionprivate function processpasscommand() as ftp_response_codes dim strresponse as string dim strdata as string on error goto processpasscommand_err_handler wsccontrol.senddata pass & m_strpassword & vbcrlf debug.print pass & m_strpassword m_objtimeout.starttimer do doevents if m_objtimeout.timeout then m_lasterror = error_ftp_user_timeout exit do end if if len(m_strwinsockbuffer) response_code_lenght then strdata = m_strwinsockbuffer exit do end if loop m_objtimeout.stoptimer if getresponsecode(strdata) = ftp_response_user_logged_in then do doevents if instr(1, m_strwinsockbuffer, 230 ) 0 then processpasscommand = ftp_response_user_logged_in m_strwinsockbuffer = exit function end if loop else processftpresponse getresponsecode(strdata) end if processpasscommand = getresponsecode(strdata) exit_label: exit functionprocesspasscommand_err_handler: if not processwinsockerror(err.number, err.description) then err.raise vbobjecterror + 1000 + err.number, cftpconnection.processpasscommand, err.description end if goto exit_label end function 下面方法附加到pass命令中發(fā)送到服務器，并處理服務器的響應。private function processpwdcommand() as boolean dim strresponse as string dim strdata as string on error goto processpwdcommand_err_handler wsccontrol.senddata pwd & vbcrlf debug.print pwd m_objtimeout.starttimer do doevents if m_objtimeout.timeout then m_lasterror = error_ftp_user_timeout exit do end if if instr(1, m_strwinsockbuffer, vbcrlf) 0 then strdata = m_strwinsockbuffer m_strwinsockbuffer = exit do end if loop m_objtimeout.stoptimer if getresponsecode(strdata) = ftp_response_pathname_created then dim intposa as integer, intposb as integer intposa = instr(1, strdata, chr$(34) + 1 intposb = instr(intposa, strdata, chr$(34) if intposa 1 and intposb 0 then m_strcurrentdirectory = mid$(strdata, intposa, intposb - intposa) processpwdcommand = true else raise error - unknown response format end if else processftpresponse getresponsecode(strdata) end if exit_label: exit functionprocesspwdcommand_err_handler: if not processwinsockerror(err.number, err.description) then err.raise vbobjecterror + 1000 + err.number, cftpconnection.processpwdcommand, err.description end if goto exit_label end functionprivate sub class_terminate() call breakeconnection set wscdata = nothing set wsccontrol = nothing m_objtimeout.stoptimer set m_objtimeout = nothing end subprivate sub wsccontrol_dataarrival(byval bytestotal as long) dim strdata as string wsccontrol.getdata strdata m_strwinsockbuffer = m_strwinsockbuffer & strdata m_strlastserverresponse = strdata m_objtimeout.reset if getresponsecode(strdata) = 426 then if m_btransferinprogress or m_buploadfile then wscdata.close close m_intlocalfileid m_strdatabuffer = m_ldownloadedbytes = 0 m_luploadedbytes = 0 m_btransferinprogress = false m_buploadfile = false m_bfileisopened = false end if wsccontrol.close m_bbusy = false end if debug.print left(strdata, len(strdata) - 2) end subprivate function processportcommand() as boolean dim intport as integer dim stripaddress as string dim colipaddresses as new collection dim strsend as string dim strdata as string on error resume next raiseevent statechanged(ftp_establishing_data_connection) do intport = getfreeport if wscdata.state sckclosed then wscdata.close wscdata.localport = intport wscdata.listen if not err then exit do loop on error goto processportcommand_err_handler stripaddress = cstr(wsccontrol.localip) strsend = port & replace(stripaddress, ., ,) strsend = strsend & , & intport 256 & , & (intport mod 256) strsend = strsend & vbcrlf wsccontrol.senddata strsend debug.print left(strsend, len(strsend) - 2) m_objtimeout.starttimer do doevents if m_objtimeout.timeout then m_lasterror = error_ftp_user_timeout exit do end if if instr(1, m_strwinsockbuffer, vbcrlf) 0 then strdata = m_strwinsockbuffer m_strwinsockbuffer = exit do end if loop m_objtimeout.stoptimer if getresponsecode(strdata) = ftp_response_command_ok then processportcommand = true raiseevent statechanged(ftp_data_connection_established) else processftpresponse getresponsecode(strdata) end if exit_label: exit functionprocessportcommand_err_handler: if not processwinsockerror(err.number, err.description) then err.raise vbobjecterror + 1000 + err.number, cftpconnection.processportcommand, err.description end if goto exit_label end function在和服務器連接之前，首先要保證服務器的地址不為空，關(guān)閉wsccontrol將連接設為0，連接服務器。啟動定時器，如果超時，就退出，否則檢查wsccontrol的狀態(tài)，并進行相應的處理。public function connect() as booleanon error goto connect_err_handlerdim strdata as stringm_strwinsockbuffer = m_bbusy = trueif len(m_varftpserver) 0 then with wsccontrol .close .localport = 0 .connect m_varftpserver, 21 m_objtimeout.starttimer do doevents if m_objtimeout.timeout then m_lasterror = error_ftp_user_timeout exit do end if if .state = sckconnected then m_objtimeout.stoptimer raiseevent statechanged(ftp_connection_connected) m_objtimeout.starttimer do doevents if m_objtimeout.timeout then m_lasterror = error_ftp_user_timeout exit do end if if len(m_strwinsockbuffer) (response_code_lenght - 1) then strdata = m_strwinsockbuffer m_strwinsockbuffer = exit do end if loop m_objtimeout.stoptimer select case getresponsecode(strdata) case ftp_response_service_ready_for_new_user select case processusercommand case ftp_response_user_logged_in connect = true case ftp_response_user_name_ok_need_password if processpasscommand = ftp_response_user_logged_in then connect = true end if end select get working directory if connect then call processpwdcommand end if case ftp_response_service_ready_in_minutes 120 service ready in nnn minutes. m_lasterror = error_ftp_protocol_service_ready_in_minutes case ftp_response_service_not_available_closing_control_connection 421 service not available, closing control connection. m_lasterror = error_ftp_protocol_service_not_available_closing_control_connection end select exit do elseif .state = sckconnectaborted then m_lasterror = error_ftp_winsock_connectaborted elseif .state = sckresolvinghost then raiseevent statechanged(ftp_connection_resolving_host) elseif .state = sckhostresolved then raiseevent statechanged(ftp_connection_host_resolved) end if loop m_objtimeout.stoptimer end withelse raise error connect = false exit functionend ifexit_label: if connect then raiseevent statechanged(ftp_user_logged) m_bbusy = false exit functionconnect_err_handler: if not processwinsockerror(err.number, err.description) then err.raise vbobjecterror + 1000 + err.number, cftpconnection.connect, err.description end if goto exit_label end function下載文件：文件傳輸涉及到重新開始命令和獲得文件命令。重新開始命令的命令參數(shù)域代表服務器要重新開始的那一點，此命令并不傳送文件，而是簡單指定點后的數(shù)據(jù)，獲得文件命令使服務器dtp傳送指定路徑內(nèi)的文件副本到服務器或用戶dtp，這邊服務器上文件的狀態(tài)和內(nèi)容不受影響。processrestcommand方法向ftp服務器發(fā)送rest命令，告訴服務器文件要開始傳輸?shù)奈恢?，并處理服務器的響應。如果成功返回true，反之返回false。private function processrestcommand(lstartpoint as long) as boolean dim strresponse as string dim strdata as string on error goto processrestcommand_err_handler wsccontrol.senddata rest & lstartpoint & vbcrlf debug.print rest & lstartpoint m_objtimeout.starttimer do doevents if m_objtimeout.timeout then m_lasterror = error_ftp_user_timeout exit do end if if instr(1, m_strwinsockbuffer, vbcrlf) 0 then strdata = m_strwinsockbuffer m_strwinsockbuffer = exit do end if loop m_objtimeout.stoptimer if getresponsecode(strdata) = ftp_response_requested_file_action_pending_further_info then processrestcommand = true else processftpresponse getresponsecode(strdata) end if exit_label: exit functionprocessrestcommand_err_handler: if not processwinsockerror(err.number, err.description) then err.raise vbobjecterror + 1000 + err.number, cftpconnection.processrestcommand, err.description end if goto exit_label end functionprocessretrcommand方法向ftp服務器發(fā)送rest命令，讓ftp服務器傳送指定路徑的文件副本到本地，并處理服務器的響應。如果成功返回true，反之返回false。private function processretrcommand(strfilename as string, lstartpoint as long) as boolean dim strresponse as string dim strdata as string on error goto processretrcommand_err_handler m_strdatabuffer = wsccontrol.senddata retr & strfilename & vbcrlf debug.print retr & strfilename m_objtimeout.starttimer do doevents if m_objtimeout.timeout then m_lasterror = error_ftp_user_timeout exit do end if if not m_btransferinprogress then strdata = m_strwinsockbuffer exit do end if if instr(1, m_strwinsockbuffer, vbcrlf) 0 then if getresponsecode(m_strwinsockbuffer) = 150 or _ getresponsecode(m_strwinsockbuffer) = 125 then if lstartpoint = 0 and fileexists(m_strlocalfilepath) then kill m_strlocalfilepath end if m_intlocalfileid = freefile open m_strlocalfilepath for binary as m_intlocalfileid if lstartpoint 0 then seek m_intlocalfileid, lstartpoint + 1 end if turn on flag m_bfileisopened m_bfileisopened = true ignore 150 and 125 reply codes m_strwinsockbuffer = mid$(m_strwinsockbuffer, instr(1, m_strwinsockbuffer, vbcrlf) + 2) raiseevent statechanged(ftp_transfer_starting) else strdata = m_strwinsockbuffe