ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng)/ProfitPress-MegaCDROM2.B6I/MISC/NETWORK/TEL23DOC.ZIP/CHAP.5

Text File | 1991-07-01 | 18.1 KB | 573 lines

5.1    NCSA Telnet


File Transfer    5.1


National Center for Supercomputing Applications


June 1991








5.1    NCSA Telnet

File Transfer    5.1

National Center for Supercomputing Applications

June 1991




    6/30/91




Chapter 5    File Transfer



Chapter Overview
File Transfer Terminology
File Transfer Guidelines
Full Path Specification:  Conversion of Forward
Slashes
Simultaneous Activity
Rules for Filenames Sent to the PC
File Transfer Reports
File Transfer Using FTP
Setting Up FTP
Using FTP
Invoking FTP on the Host Computer
Invoking FTP Using Alternate Methods
Using FTP Commands
File Transfer Using rcp
Setting Up rcp
Using rcp
Avoiding Use of NCSA Telnet's rcp Server
Using rcp Between the PC and UNIX
Using Wildcards

Chapter Overview

This chapter describes procedures for transferring files between a
PC and a network host, using NCSA Telnet's two built-in file
transfer servers: FTP and rcp. Guidelines and information are
presented for file name conventions, path specification, and
background file transfer.


File Transfer Terminology

This chapter uses the following terms:


ASCII file, text file
Humans can read an ascii or text file, and can edit the files using
standard editors on the PC or host. When you transfer text files,
their end-of-line markers are changed.


Binary, Graphics, or Image File
Humans can't read a binary, graphics, or image file.
When transferred, binary files are not changed in any way
(unlike text files).


Client/Server
The client is the system that requests services while the server is
the system that provides or "serves" them. The client is not always
your PC, despite appearances. When you use NCSA Telnet to
connect to a host, your PC is the telnet client. When you request a
file transfer from your PC, the transfer is actually initiated on the
host, making the host the FTP client and your PC the FTP server.
Thus, the PC is a telnet client and an FTP server at the same time.


File Transfer
In a file transfer, the contents of a file are copied, and the copy is
placed on another computer's disk drive.


File Transfer Guidelines

Full Path Specification:
Conversion of Forward
Slashes
If you do not specify a full pathname for either FTP or rcp, NCSA
Telnet will transfer the files to the default directory. If you need to
specify a different directory, type the full pathname as documented
in the DOS manual. The full pathname may include the disk drive
name, with a colon. For example:

D:\myfiles\graphics\image.dat

or

D:/myfiles/graphics/image.dat

You may use forward slashes (/) rather than backslashes (\),
because NCSA Telnet automatically converts any forward slashes
in UNIX pathnames to backslashes for compatibility with PC-DOS.
Because backslashes are special characters in the UNIX shell and
a special format is required to enter them, forward slashes are
more convenient to use.

NOTE:  rcp is a Berkeley UNIX feature. Refer to the section,
"Using rcp File Transfer," in this chapter for more information.


Simultaneous Activity
With both FTP and rcp, file transfers are processed at the same
time as other telnet sessions. Therefore, while a file transfer is in
progress, you can perform other NCSA Telnet activities such as
interacting with a telnet session, switching sessions, adding new
sessions, or changing parameters.

However, do not initiate another file transfer while one is already
in progress. While an FTP request is being processed, a second
FTP request will be ignored. Furthermore, if you try to start an rcp
transfer while another transfer is already underway, both
transfers may fail.

NOTE: Do not quit NCSA Telnet while a file transfer is in
progress, because the file transfer may fail.


Rules for Filenames Sent to
the PC
Whether you are using FTP or rcp to transfer files to or from a PC,
check these rules for PC filenames:

Ñ    A legal PC filename is eight characters or less, followed by an
optional period and an up to three-character extension.

Ñ    Upper and lower case are considered identical for filenames on
PC disks.

Ñ    Names of files which are transferred from the PC are given in
all lower case.

Ñ    A filename longer than eight characters is truncated.

Ñ    If a period occurs in a filename, the next three characters are
read as the extension, and any others are truncated.

Ñ    A filename should not contain "special characters" or spaces.
If it does, the file may be lost or unreadable. Examples of special
characters are the asterisk (*), the dollar sign ($), the pound
sign (#), the hyphen (-), and control characters.


File Transfer Reports
The FTP server produces several kinds of information for you to
help keep tabs on FTP access to the local hard disk. You can view
this information by pressing the ALT-Z keys (show console
messages), as documented in Chapter 2, "Introduction to
Managing Sessions." The following list describes the
information which FTP provides.

Ñ    Reports when a command connection is initiated, with the IP
address or host name of the remote machine which initiated the
connection

Ñ    Reports the name of the user who logs in, if you use the USER
command

Ñ    Reports the file names which were transferred to or from local
disk

Ñ    Reports when the command connection ends

The rcp server also produces reports for the console screen.

Ñ    Reports when an rcp transfer begins
Ñ    Reports when the rcp transfer ends


File Transfer Using FTP

The FTP server in NCSA Telnet is the minimum standard FTP
server, similar to that in 4.2 BSD UNIX. NCSA's FTP supports the
following features:

Ñ    Stream transfer in text format (ASCII) or binary format
(IMAGE)

Ñ    Change, create, or delete a directory

Ñ    Print current directory

Ñ    List files in current directory (with wildcard specifications)

Ñ    Send and receive multiple files with one command, using
wildcards
Ñ    Delete file


Setting Up FTP
The host machine must support FTP file transfer. If you do not
know whether it does, see your system administrator.

You must not have disabled the file transfer capability of NCSA
Telnet. That is done with the Parameter menu (see Chapter 3,
"More About Managing Sessions"), or in the configuration file
(see Chapter 7, "Installation and Configuration"). If the file
transfer capability has been switched off, when you attempt to start
up FTP, you will get a message from the host to the effect that the
computer is not responding. If you get such a message, check the
file transfer mode on the Parameter menu to make sure that it is
enabled.


Using FTP
Use FTP rather than rcp in either of the following situations.

1.    You are not thoroughly familiar with the host operating system.
FTP is easier to use than rcp, and requires less familiarity with
the host commands and directory structure.

2.    You are transferring PC text (ASCII) files to a host. FTP is a
better choice than rcp, because FTP automatically converts the
end-of-line characters in text files from CRLF, used by PC-DOS,
to LF, used by UNIX machines.


Invoking FTP on the Host
Computer
FTP is initiated by the host, so the FTP commands vary,
depending on the host system. For full documentation of FTP and
commands within FTP, you must refer to the manuals for the host
computer. With UNIX systems, you can see online documentation
by using the man ftp command. See Chapter 4, "Utility
Programs," for more information.


The FTP Command
On most systems, the FTP command is entered at the prompt, with
the name or IP address of the target machine. For example, if your
PC is named "mymachine" and your IP address is 192.17.20.22,
then you might enter:

% ftp mymachine

or

% ftp 192.17.20.22

which generates a response like this:

Connected to 192.17.20.22.
220 PC Resident FTP server, ready
Name (192.17.20.22:timk):
Most FTP clients will now prompt you for your username and
password. If NCSA Telnet is configured for passwords (see
Chapter 7, "Installation and Configuration"), then these are
required. Otherwise, just press RETURN to bypass the prompts. If
you are  not prompted for username and password, then assume
that you are logged in and continue with your FTP commands.


Invoking FTP Using
Alternate Methods
The most common procedure for starting FTP uses the shortcut
keystroke, ALT-F. When you press ALT-F, NCSA Telnet types the
FTP command described above, automatically including your
PC's IP address and the RETURN to initiate the command. For
convenience, you will probably prefer ALT-F to the other ways of
entering the command. You may want to think of this as a
keyboard macro that is pre-set with the FTP command and your IP
address.

Another available macro is ALT-I which types your IP address for
you. When entering any networking command, FTP for example,
you can instantly produce your own network IP address with ALT-
I. The following sequence is equivalent to pressing ALT-F.

ftp
(SPACEBAR)
(ALT-I)
(RETURN)

Use whichever method of invoking FTP that works best for you.
Your host computer may or may not accept FTP commands as
described here, so you may have to try some variations to find the
easiest method for your site. Your system administrator may be
able to help.


Using FTP Commands
For most FTPs, after FTP has been invoked and passwords have
been checked, you are prompted for individual FTP commands.
These commands are also documented in the manuals for the host
computer. Most of the FTP implementations have similar
commands because they are modeled after the Berkeley UNIX
version of FTP. Table 5.1 lists FTP commands that are common to
most implementations.

Table 5.1    Common FTP
Commands
Command        Action

ascii        Sets mode to ASCII transfer mode (default)

binary        Sets mode to binary (image) transfer mode

cd path        Sets a new default directory on PC

dir            Shows filenames in PC's default directory

get filename    Gets a file from PC and sends it to host

help            Shows online list of FTP commands

put filename    Sends a file from host to PC

pwd            Shows current PC directory name

quit            Exits FTP

remotehelp    Shows list of supported commands on FTP
                server


ASCII, Binary
The default mode for FTP transfers is ASCII format. If you are
transferring graphics or binary data files, change to binary mode
before you use the put or get commands. Do this by entering the
command binary. To reset the ASCII format after sending a
binary file, enter the command ascii. Figure 5.1 shows an FTP
transaction with an ASCII file. Figure 5.2 shows an FTP
transaction with a binary file.


Default Directory
Unless you include a full pathname with the command, NCSA
Telnet transfers the file to the default directory. As Table 5.1
indicates, you can use FTP commands to identify the current
directory (pwd), or change the current directory (cd).

The change directory command, which you type as cd, allows you
to change the default disk drive in addition to the default directory.
Just use PC standard disk notation, with forward slashes instead
of backslashes, for example:

ftp> cd D:/files

The pwd command also returns disk information. After the
previous example cd command, a pwd command returns:

D:\FILES


Transfer to the PC
Even though you seem to be initiating the transfer from the PC, the
transaction operates from the host's side. The practical effect of
this could make the commands seem intuitively "backwards." To
transfer a file from the host to your PC, you use a put command.
The form this command takes is:

put filename.ext

Figure 5.1 shows an example of a put command used with an
actual file, named temp2. The boldface type represents user
entries.


Figure 5.1    Put to the PC, ASCII
File
newton_45% ftp -n 192.17.20.124
Connected to 192.17.20.124.
220 PC Resident FTP server, ready
ftp> put temp2
200 This space intentionally left blank <  >
150 Opening connection
226 Transfer complete
262145 bytes sent in 32.61 seconds (7.8 Kbytes/s)
ftp> quit
221 Goodbye
newton_46%



Transfer to the Host
A request to send a file from the PC to the host is called a get.

get filename.ext

Figure 5.2 shows a get operation, using a binary file named
bridge.pic. Note that the file was in the directory named ibmg, so
the cd command was used. Again, the boldface type represents user
entries. If a text file were to be sent after this, the ASCII mode would
have to be reset, using the FTP ascii command.

Figure 5.2     Get from the PC,
Binary File
newton_41% ftp -n 192.17.20.124
Connected to 192.17.20.124.
220 PC Resident FTP server, ready
ftp> bin
200 Type set to I, binary transfer mode
ftp> cd /ibmg
250 Chdir okay
ftp> get bridge.pic
200 This space intentionally left blank <  >
150 Opening connection
226 Transfer complete
262144 bytes received in 9.22 seconds (28 Kbytes/s)
ftp>
ftp> quit
221 Goodbye
newton_42%



FTP Status Indicator
After you have entered a put or get command, in the lower right
hand corner of your screen you will see the filename and an
indication of the number of bytes transferred (in the case of a put)
or left to be transferred (in the case of a get). These numbers are
updated every couple of seconds to help you keep track of the
progress of the file transfer. After the command has completed, the
filename goes away and the host usually prints a confirmation
message, as seen in Figures 5.1 and 5.2.


mput, mget
On many telnet hosts, you can transfer multiple files sequentially
with one command, either mput or mget, used with wildcard
characters. (PC wildcard characters are ? for a single character
and * for multiple characters.) For instance, to transfer the
multiple files, teln.2, and teln.3, you could enter mget (or mput)á*


Bug with mget
If you transfer multiple binary files using a UNIX host, note that
there is a bug in mget as implemented on some systems (especially
4.2 BSD UNIX). When used in binary mode, mget adds a carriage
return to the filenames as they are transferred. The files
themselves are not affected. Use a UNIX utility to remove the
carriage return from the filename. In ASCII mode, there is no
problem.


File Transfer Using rcp

rcp is a Berkeley UNIX feature found in Sun UNIX and other 4.2
BSD systems. The rcp program cannot do the end of line
translation required for text files, so it is typically used for binary
files only. UNIX rcp is designed for files copied UNIX-to-UNIX,
but NCSA Telnet's rcp server supports transfer between a UNIX
system and a PC.

NOTE: NCSA Telnet's rcp server does not support the recursive
option (-r).


Setting Up rcp
To use rcp efficiently, you should be familiar with the UNIX host,
including:

Ñ    rcp command and options
Ñ    directory structures used with rcp
Ñ    the relationship between the UNIX shell and rcp wildcards

Details on these concepts are in the manuals for UNIX.

The internet (IP) number and machine name for each PC must be
in the UNIX /etc/hosts file for every machine that is
transferring files to and from your PC. If rcp does not recognize
your PC's name, have your system administrator check or add that
name in the UNIX machine's hosts file.


Using rcp
Use rcp for binary transfers to or from a UNIX system if you are
familiar with the UNIX hosts, as described earlier.

There are two advantages of using rcp rather than FTP, on binary
file transfers to or from a UNIX machine.

Ñ    rcp handles wildcards more efficiently than FTP does.
Ñ    rcp handles directories more easily than FTP does.


Avoiding Use of NCSA
Telnet's rcp Server
Do not use the rcp server to transfer text files. Text files on the PC
contain extra RETURN characters that NCSA Telnet's rcp server
does not remove when transferring to UNIX.

NOTE: Do not initiate an rcp while a file transfer is already in
process, or both transfers may fail.


Using rcp Between the PC
and UNIX
The rcp program is fully documented in the manuals for UNIX
hosts that support rcp transfers. Refer to those manuals to learn
about rcp. As a reminder, the general syntax of the rcp command is
given here. The target filename can be a directory name and
wildcards are allowed, as noted in the next section.

% rcp mypc:filename unixfile        From PC to UNIX
% rcp unixfile mypc:filename        From UNIX to PC


Example: PC to UNIX
Following is a sample command to transfer a file named image
from the PC named mypc to the current directory on the UNIX host
(indicated by a dot or period). Note that the only blank spaces are
after the command rcp, and between the filename and the target
directory name (in this case, the dot for the current directory).

% rcp mypc:image .


Example: UNIX to PC
Following is a sample command to transfer a file named mygraf
in the directory graphs from the UNIX host and put it in the
directory grafs on the PC.

% rcp /graphs/mygraf mypc:/grafs


Using Wildcards
You can use wildcard characters with the rcp command to transfer
multiple files between a PC client and a UNIX host. Wildcards that
refer to UNIX files should be in the UNIX regular expression
format. You must set wildcards that refer to PC files apart by using
backslashes or quotes. See the following examples.


Example: Backslashes Used With Wildcards
One way of using PC wildcards with the rcp server is to use the
backslash character (\) to keep the UNIX shell from interpreting
the special characters. Suppose you want to transfer all files that
have image at the beginning of the filename. Instead of the usual
PC format, image*.*, you must precede each asterisk with a
backslash. The full rcp command would look like this:

% rcp mypc:image\*.\* .

Without the backslashes, the UNIX shell would try to translate the
asterisk on the host rather than on the PC.


Example: Quotes Used With Wildcards
The second way of using PC wildcards with the rcp server is to
insert quotes around the entire argument. The command to
transfer the files beginning with image would look like this:

% rcp "mypc:image*.*" .