📄 tyt06fi.htm
字号:
230 User tparker logged in.
Remote system type is UNIX.
Using binary mode to transfer files.</FONT></PRE>
<P>On large networks where a system such as Yellow Pages (YP) or Network Information Services (NIS) is used, FTP logins are usually permitted on most machines. If YP or NIS is not employed, you must be in the valid users file to obtain FTP access. As with Telnet, you can log into the remote with a different user ID from your local machine login. To transfer files, you must have the proper permissions on the remote, if file permissions are provided for by the operating system.
<BR>
<P>After logging into another machine using FTP, you are not actually on the remote machine. You are still logically on the client, so all instructions for file transfers and directory movement must be with respect to your local machine, not the remote one. Note that this is the opposite of Telnet (a distinction that causes considerable confusion among newcomers to FTP and Telnet).
<BR>
<P>Remember that all references to files and directories are relative to the machine that initiated the FTP session. If you are not careful, you can accidentally overwrite existing files.
<P>The process followed by FTP when a connection is established is as follows:
<BR>
<OL>
<LI><B>Login: </B>Verifies the user ID and password.
<BR></LI>
<BR>
<LI><B>Define directory: </B>Identifies the starting directory.
<BR></LI>
<BR>
<LI><B>Define file transfer mode: </B>Defines the type of transfer.
<BR></LI>
<BR>
<LI><B>Start data transfer: </B>Enables user commands.
<BR></LI>
<BR>
<LI><B>Stop data transfer: </B>Closes the connection.
<BR></LI>
<BR>
</OL>
<P>The steps are performed in sequence for each connection. A user has several commands available to control FTP; the most frequently used commands are summarized in Table 6.6.
<BR>
<BR>
<P ALIGN=CENTER>
<CENTER>
<FONT COLOR="#000080"><B>Table 6.6. FTP user commands.</B></FONT></CENTER>
<BR>
<CENTER><TABLE BORDERCOLOR=#000040 BORDER=1 CELLSPACING=2 CELLPADDING=3 >
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P><B><I>FTP Command</I></B>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P><B><I>Description</I></B>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>ascii
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Switch to ASCII transfer mode
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>binary
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Switch to binary transfer mode
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>cd
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Change directory on the server
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>close
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Terminate the connection
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>del
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Delete a file on the server
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>dir
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Display the server directory
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>get
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Fetch a file from the server
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>hash
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Display a pound character for each block transmitted
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>help
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Display help
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>lcd
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Change directory on the client
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>mget
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Fetch several files from the server
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>mput
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Send several files to the server
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>open
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Connect to a server
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>put
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Send a file to the server
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>pwd
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Display the current server directory
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>quote
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Supply an FTP command directly
<BR>
</FONT>
<TR>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>quit
<BR>
</FONT>
<TD BGCOLOR=#80FFFF ><FONT COLOR=#000080>
<P>Terminate the FTP session</FONT>
</TABLE></CENTER><BR>
<P>Using FTP is similar to Telnet, except that all movements of files are relative to the client. Therefore, putting a file is moving it from the client to the server, whereas getting a file is the reverse. A sample FTP session follows:
<BR>
<PRE>
<FONT COLOR="#000080">tpci_hpws1-1> ftp tpci_hpws4
Connected to tpci_hpws4.
220 tpci_hpws4 FTP server (Version 1.7.109.2 Tue Jul 28 23:32:34 GMT 1992) ready.
Name (tpci_hpws4:tparker):
331 Password required for tparker.
Password:
230 User tparker logged in.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> pwd
257 "/u1/tparker" is current directory.
ftp> get mandelfile1.gif
remote: mandelfile1.gif local: mandelfi.gif
200 PORT command successful
150 Opening BINARY mode data connection for mandelfile1.gif
226 File transfer complete
1192834 bytes sent in 0.89 seconds
ftp> <Ctrl+d>
tpci_hpws1-2></FONT></PRE>
<P>In this short sample, I transferred a file called mandelfile1.gif from a UNIX machine (the server) to the local machine (the client). You might have noticed that the filename was truncated automatically by the server to fit the DOS filesystem naming conventions. Also, note that I used binary mode (which was the system default). If the default had been ASCII mode, I would have just transferred over a megabyte of total garbage that couldn't be used for anything.
<BR>
<P>A debugging option is available from the command line by adding -d to the command. This displays the command channel instructions. Instructions from the client are shown with an arrow as the first character, whereas instructions from the server have three digits in front of them. A PORT in the command line indicates the address of the data channel on which the client is waiting for the server's reply. If no PORT is specified, channel 20 (the default value) is used. Unfortunately, the progress of data transfers cannot be followed in the debugging mode. A sample session with the debug option enabled is shown here:
<BR>
<PRE>
<FONT COLOR="#000080">tpci_hpws1-1> ftp -d
ftp> open tpci_hpws4
Connected to tpci_hpws4.
220 tpci_hpws4 FTP server Name (tpci_hpws4:tparker):
---> USER tparker
331 Password required for tparker.
Password:
---> PASS qwerty5
230 User tparker logged in.
---> SYST
215 UNIX Type: L8
Remote system type is UNIX.
---> Type I
200 Type set to I.
Using binary mode to transfer files.
ftp> ls
---> PORT 47,80,10,28,4,175
200 PORT command successful.
---> TYPE A
200 Type set to A.
---> LIST
150 Opening ASCII mode data connection for /bin/ls.
total 4
-rw-r----- 1 tparker tpci 2803 Apr 29 10:46 file1
-rw-rw-r-- 1 tparker tpci 1286 Apr 14 10:46 file5_draft
-rwxr----- 2 tparker tpci 15635 Mar 14 23:23 test_comp_1
-rw-r----- 1 tparker tpci 52 Apr 22 12:19 xyzzy
Transfer complete.
---> TYPE I
200 Type set to I.
ftp> <Ctrl+d>
tpci_hpws1-2></FONT></PRE>
<P>You might notice in the previous code how the mode changes from binary to ASCII to send the directory listing, and then back to binary (the system default value). You can see how the two systems communicate to display the status messages that appear without the debugging option active.
<BR>
<P>When FTP is used in a graphical user environment, you might be able to use a GUI-based tool. For example, NetManage's ChameleonNFS provides the FTP utility shown in Figure 6.8. In this case, the NFS client on the Windows for Workgroups machine has connected to a UNIX server. The Local side of the window shows the Windows machine, and the Remote side of the window shows the UNIX box's current filesystem contents. When using a GUI-based utility like this one, you can use the mouse and various buttons to transfer files back and forth between machines.
<BR>
<P><B><A HREF="06tyt08.gif" tppabs="http://www.mcp.com/817948800/0-672/0-672-30885-1/06tyt08.gif">Figure 6.8. Many operating systems have a GUI-based </B><B>FTP client.</A></B>
<BR>
<BR>
<A ID="E69E87" NAME="E69E87"></A>
<H4 ALIGN=CENTER>
<CENTER>
<FONT SIZE=4 COLOR="#FF0000"><B>FTP Third-Party Transfers</B></FONT></CENTER></H4>
<BR>
<P>FTP enables a transfer to occur through a third machine positioned between the client and the server. This procedure is known as a <I>third-party transfer</I> and is sometimes necessary to obtain proper permissions to access the remote machine. Figure 6.9 shows the schematic of a third-party transfer, with the control connection made through a third machine.
<BR>
<P><B><A HREF="06tyt09.gif" tppabs="http://www.mcp.com/817948800/0-672/0-672-30885-1/06tyt09.gif">Figure 6.9. A third-party FTP transfer.</A></B>
<BR>
<P>When setting up a third-party connection, the client opens the control connections between the remote machine and the second client that handles the control channel. Only the control channel goes through the second client, whereas the data channel goes directly between the two ends.
<BR>
<P>When a transfer request is submitted, it is transferred through the second client, which checks permissions and then forwards the request to the server. The data transfer can take place directly, because the permissions were checked on the control channel.
<BR>
<BR>
<A ID="E69E88" NAME="E69E88"></A>
<H4 ALIGN=CENTER>
<CENTER>
<FONT SIZE=4 COLOR="#FF0000"><B>Anonymous FTP Access</B></FONT></CENTER></H4>
<BR>
<P>FTP requires a user ID and password to enable file transfer capabilities, but there is a more liberal method of enabling general access to a file or directory, called <I>anonymous FTP.</I> Anonymous FTP removes the requirement for a login account on the remote machine, usually enabling the login anonymous with a password of either guest or the user's actual login name. The following session shows the use of an anonymous FTP system:
<BR>
<PRE>
<FONT COLOR="#000080">tpci_hpws4-1> ftp uofo.edu
Connected to uofo.edu.
220 uofo.edu FTP server (Version 1.7.109.2 Tue Jul 28 23:32:34 GMT 1992) ready.
Name (uofo:username): anonymous
331 Guest login ok, send userID as password.
Password: tparker
230 Guest login ok, access restrictions apply.
ftp> <Ctrl+d>
tpci_hpws4-2></FONT></PRE>
<P>If the remote system is set to enable anonymous logins, you are prompted for a password and then given a warning about access limitations. If there is a file on the remote system you require, a get command transfers it. Anonymous FTP sites are becoming common, especially with the popularity of the Internet.
<BR>
<BR>
<A ID="E69E89" NAME="E69E89"></A>
<H4 ALIGN=CENTER>
<CENTER>
<FONT SIZE=4 COLOR="#FF0000"><B>FTP Servers</B></FONT></CENTER></H4>
<BR>
<P>Most UNIX machines act as FTP servers by default. To provide FTP server facilities, they run the daemon ftpd when the operating system is booted. The daemon is usually handled by the UNIX inetd process. When you start using inetd, the inetd daemon watches the TCP command port (channel 21) for an arriving request for a connection, then starts ftpd to service that request. If you want to ensure that your UNIX or Linux system can handle FTP requests, make sure the ftpd daemon can be started when needed by inetd by checking the inetd configuration file (usually /etc/inetd.config or /etc/inetd.conf) for a line that looks like this:
<BR>
<BR>
<PRE>
<FONT COLOR="#000080">ftp stream tcp nowait root /usr/etc/ftpd ftpd -l</FONT></PRE>
<P>If this line doesn't exist, you should add it. With most UNIX systems this line is already in the inetd configuration file, although it might be commented out, in which case you should remove the comment symbol.
<BR>
<P>Windows, Windows for Workgroups, and Windows 95 all lack an FTP server program as part of their distribution software (although Windows 95 does have an FTP client), so you have to add a commercial package. Many commercial TCP/IP suites include an FTP server process. Figure 6.10 shows the NetManage ChameleonNFS program group, which includes an FTP server program you can use as an example for Windows for Workgroups and Windows 3.<I>x</I> machines.
<BR>
<P><B><A HREF="06tyt10.gif" tppabs="http://www.mcp.com/817948800/0-672/0-672-30885-1/06tyt10.gif">Figure 6.10. The NetManage FTP Server dialog </B><B>handles the FTP server process.</A></B>
<BR>
<P>To start the NetManage FTP Server software, double-click the FTP server icon in the NetManage program group. A dialog, shown in Figure 6.10, appears. The FTP server process is now active, and anyone on another machine on your local area network can now connect to your machine, assuming they have access.
<BR>
<P>Access to your FTP service is controlled through the user lists maintained by the FTP Server package. Selecting the Users menu option from the NetManage FTP Server dialog opens the Users dialog, shown in Figure 6.11. This lets you add user names to your system. If another user on a different machine tries to connect to your FTP server software, the server verifies that their login name and password match the name and password you enter in this dialog. This lets you set up a list of users who can transfer files to and from your system, as long as the FTP server is running.
<BR>
<P><B><A HREF="06tyt11.gif" tppabs="http://www.mcp.com/817948800/0-672/0-672-30885-1/06tyt11.gif">Figure 6.11. Access to your machine is controlled </B><B>through the FTP Server Users dialog.</A></B>
<BR>
<P>If you are running an FTP server process, it is often a good idea to create a directory just for FTP. Many users prefer to create a directory called public, which is where all files to be transferred in and out of the local system are placed. This lets you prevent accidental deletion or transfer of files in other directories on your system, as well as providing you with the opportunity to filter incoming material for suitability, viruses, and so on. If you use a transfer directory, check it regularly and make sure all users who have access to your system can work only in that directory.
<BR>
<P>If you want to provide an anonymous or guest account for users on your LAN or any other network that can connect to your machine, you should set up an account with either no password or a simple password like guest. It is very important to restrict the areas a guest or anonymous login can use.
<BR>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -