計(jì)算機(jī)網(wǎng)絡(luò)實(shí)驗(yàn)課件：文件傳輸服務(wù)FTP

1、文件傳輸協(xié)議FTP主要內(nèi)容文件傳輸協(xié)議FTPFTP 功能FTP服務(wù)的工作過(guò)程FTP訪問方式FTP的工作原理FTP命令及響應(yīng)編碼文件傳輸協(xié)議FTP文件傳輸是TCP/IP中使用最廣泛的應(yīng)用之一文件傳輸協(xié)議FTP (File Transfer Protocol)的主要功能是完成從一個(gè)系統(tǒng)到另一個(gè)系統(tǒng)的完整的文件拷貝FTP并不是針對(duì)某種具體操作系統(tǒng)或某類具體文件而設(shè)計(jì)的文件傳輸協(xié)議它通過(guò)一些規(guī)程，利用網(wǎng)絡(luò)低層提供的服務(wù)，屏蔽了各種計(jì)算機(jī)系統(tǒng)的細(xì)節(jié)來(lái)完成文件傳輸?shù)娜蝿?wù)它只提供文件傳送的一些基本的服務(wù)，可以在異構(gòu)網(wǎng)中任意計(jì)算機(jī)間傳送文件網(wǎng)絡(luò)環(huán)境下復(fù)制文件的復(fù)雜性由眾多的計(jì)算機(jī)廠商研制出的文件系統(tǒng)多達(dá)數(shù)百種

2、，且差別很大：計(jì)算機(jī)存儲(chǔ)數(shù)據(jù)的格式不同。文件的目錄結(jié)構(gòu)和文件命名的規(guī)定不同。對(duì)于相同的文件存取功能，操作系統(tǒng)使用的命令不同。訪問控制方法不同。因此，要實(shí)現(xiàn)不同系統(tǒng)之間的文件復(fù)制非常困難。FTP 的主要功能是減少或消除在不同操作系統(tǒng)下處理文件的不兼容性。FTP的功能FTP的主要功能包括兩個(gè)方面：文件的下載 就是將遠(yuǎn)程服務(wù)器上提供的文件下載到本地計(jì)算機(jī)上。使用FTP實(shí)現(xiàn)的文件下載與HTTP相比較，具有使用簡(jiǎn)便、支持?jǐn)帱c(diǎn)續(xù)傳和傳輸速度快的優(yōu)點(diǎn)文件的上傳 是指客戶機(jī)可以將任意類型的文件上傳到指定的FTP服務(wù)器上FTP服務(wù)支持文件上傳和下載，而HTTP僅支持文件的下載功能 FTP服務(wù)的工作過(guò)程 FTP服

3、務(wù)采用典型的客戶/服務(wù)器工作模式 FTP服務(wù)器默認(rèn)設(shè)置兩個(gè)端口21和20端口21用于監(jiān)聽FTP客戶機(jī)的連接請(qǐng)求端口20用于傳輸文件 FTP的訪問方式FTP服務(wù)分為普通FTP與匿名FTP服務(wù)兩種類型普通FTP服務(wù)要求用戶在登錄時(shí)提供正確的用戶名和用戶密碼匿名FTP服務(wù)的實(shí)質(zhì)是：提供服務(wù)的機(jī)構(gòu)在它的FTP服務(wù)器上建立一個(gè)公開賬戶（一般為anonymous），并賦予該賬戶訪問公共目錄的權(quán)限。如果用戶要訪問這些提供匿名服務(wù)的FTP服務(wù)器，可以直接訪問而不需要密碼。有些FTP服務(wù)器可能會(huì)要求用戶用自己的電子郵件地址作為用戶密碼為了保證FTP服務(wù)器的安全，幾乎所有的匿名FTP服務(wù)器都只允許用戶下載文件，而

4、不允許用戶上載文件。 FTP的特點(diǎn)FTP通常采用交互式的人機(jī)對(duì)話工作方式，使用客戶/服務(wù)器模式。一個(gè)FTP服務(wù)器可同時(shí)為多個(gè)客戶進(jìn)程提供服務(wù)服務(wù)器進(jìn)程主要分為兩大部分：一個(gè)主進(jìn)程，負(fù)責(zé)接受新的客戶請(qǐng)求并啟動(dòng)相應(yīng)的從屬進(jìn)程若干從屬進(jìn)程，負(fù)責(zé)處理具體的客戶請(qǐng)求FTP要求客戶在建立連接時(shí)必須給出服務(wù)器上的合法帳號(hào)，且允許以帳號(hào)anonymous進(jìn)行匿名訪問控制進(jìn)程數(shù)據(jù)傳送進(jìn)程用戶界面控制進(jìn)程數(shù)據(jù)傳送進(jìn)程客戶端服務(wù)器端FTP的雙重連接FTP在客戶和服務(wù)器之間要建立雙重TCP連接一條由客戶端發(fā)起的“控制連接”（21），用來(lái)傳輸FTP命令，在整個(gè)會(huì)話期間一直保持打開一條是FTP服務(wù)器端發(fā)起的“數(shù)據(jù)連接”

5、（20），用來(lái)傳輸FTP數(shù)據(jù)Internet數(shù)據(jù)連接20控制連接21主進(jìn)程的工作步驟(1) 打開熟知端口（端口號(hào)為21），使客戶進(jìn)程能夠連接上(2) 等待客戶進(jìn)程發(fā)出連接請(qǐng)求(3) 啟動(dòng)從屬進(jìn)程來(lái)處理客戶進(jìn)程發(fā)來(lái)的請(qǐng)求。從屬進(jìn)程對(duì)客 戶進(jìn)程的請(qǐng)求處理完畢后即終止，但從屬進(jìn)程在運(yùn)行期間 根據(jù)需要還可能創(chuàng)建其他一些子進(jìn)程(4) 回到等待狀態(tài)，繼續(xù)接受其他客戶進(jìn)程發(fā)來(lái)的請(qǐng)求。主進(jìn) 程與從屬進(jìn)程的處理是并發(fā)地進(jìn)行 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05

6、331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer

7、 complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.01 用戶要用 FTP 和遠(yuǎn)地主機(jī)建立連接。 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest l

8、ogin ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 s

9、econds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.02 本地 FTP 發(fā)出的連接成功信息。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD comm

10、and successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.03 從遠(yuǎn)地服務(wù)器返回的信息，

11、220 表示“服務(wù)就緒”。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 POR

12、T command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.04 本地 FTP 提示用戶鍵入名字。用戶鍵入的名字表示“匿名”。用戶只需鍵入 anonymous 即可。 FTP 的屏幕信息舉例 01 f

13、tp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 AS

14、CII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.05 數(shù)字 331 表示“用戶名正確”，需要口令。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.

15、04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).

16、13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.06 本地 FTP 提示用戶鍵入口令。用戶這時(shí)可鍵入guest 作為匿名的口令，也可以鍵入自己的電子郵件地址，即名為 xyz 的主機(jī)上的 abc。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: a

17、nonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASC

18、II Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.07 數(shù)字 230 表示用戶已經(jīng)注冊(cè)完畢。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Passw

19、ord: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488

20、bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.“ftp”是 FTP 的提示信息。用戶鍵入的是將目錄改變?yōu)榘?RFC 文件的目錄。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access res

21、trictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/

22、s).14 ftp quit15 221 Goodbye.09 字符 CWD 是 FTP 的標(biāo)準(zhǔn)命令，代表 Change Working Directory。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 2

23、50 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.10 用

24、戶要求將名為 rfc1261.txt 的文件復(fù)制到本地主機(jī)上，并改名為 nicinfo。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp ge

25、t rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.11 字符 PORT 是 FTP 的標(biāo)準(zhǔn)命令，表示要建立數(shù)據(jù)連接。200 表示

26、“命令正確”。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT comm

27、and successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.12 數(shù)字 150 表示“文件狀態(tài)正確， 即將建立數(shù)據(jù)連接”。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 ni

28、c FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1

29、261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.13 數(shù)字 226 是“釋放數(shù)據(jù)連接”?，F(xiàn)在一個(gè)新的本地文件已產(chǎn)生。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous0

30、5 331 Guest login ok, send ident as password.06 Password: abc07 230 Guest login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transf

31、er complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.14 用戶鍵入退出命令。 FTP 的屏幕信息舉例 01 ftp 02 connected to 03 220 nic FTP server (Sunos 4.1)ready.04 Name: anonymous05 331 Guest login ok, send ident as password.06 Password: abc07 230 Gue

32、st login ok, access restrictions apply.08 ftp cd rfc09 250 CWD command successful.10 ftp get rfc1261.txt nicinfo11 200 PORT command successful.12 150 ASCII data connection for rfc1261.txt (7,1401) (4318 bytes).13 226 ASCII Transfer complete. local: nicinfo remote: rfc1261.txt 4488 bytes received in 15 seconds (0.3 Kbytes/s).14 ftp quit15 221 Goodbye.15 表明 FTP 工作結(jié)束。 FTP 的屏幕信息舉例 Windows下的FTP客戶程序FTP命令行實(shí)用程序：在Windows下鍵入ftp命令即可打開MS-DOS方式的ftp交互窗，提示符為 ftp 。在ftp交互窗中可以實(shí)