ProfitPress Mega CDROM2 …eeware (MSDOS)(1992)(Eng)/ProfitPress-MegaCDROM2.B6I/MISC/NETWORK/TEL23DOC.ZIP/CHAP.2

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2.1    NCSA Telnet


Introduction to Managing Sessions    2.1


National Center for Supercomputing Applications


June 1991







2.1    NCSA Telnet

Introduction to Managing Sessions    2.1

National Center for Supercomputing Applications

June 1991




6/30/91




Chapter 2    Introduction to Managing Sessions



Chapter Overview
Keyboard Usage
Multiple Sessions
Opening Multiple Initial Sessions
Using the Status Line
Opening Additional Sessions
Indicating the Host
Estimating Host Response Time
Using Scrollback Mode
Using the Cut and Paste Functions
Switching Between Sessions (ALT-N)
Displaying Console Messages (ALT-M)
Exiting the Present Connection (ALT-X)
Capture File Operations
Designating a Capture File
Using PRN
Using One Capture at a Time

Chapter Overview

This chapter introduces NCSA Telnet's capability for multiple
connections with one or more hosts. The chapter describes
standard VT100 key emulation, keys for some common EDT
operations, how to work with multiple sessions, and operations
with the capture file.


Keyboard Usage

When NCSA Telnet is running, the PC appears to the host as a
VT100 terminal. For keys that the PC keyboard and the VT100
keyboard have in common, NCSA Telnet transmits the keystrokes
unmodified. However, the VT100 keyboard has some keys that the
PC keyboard does not have, and also treats other PC board keys
differently. Furthermore, many VT100 keys have special
meanings when they are transferred to the host. To provide full
VT100 functionality, telnet programmers have designated some
PC keys to emulate the operation of VT100 keys.

Table 2.1 lists the PC keys to use for VT100 terminal emulation.

Table 2.1    Keys Used for
VT100 Terminal
Emulation
To Send the VT100 Code    Press PC Key(s)

RETURN    ENTER

DELETE*    BACKSPACE*

BACKSPACE*    CTRL-
    BACKSPACE*

LINE FEED    CTRL-ENTER

Keypad ENTER     Keypad ENTER
(not identical to RETURN)

Keypad . (decimal point)    Keypad .

Keypad - (hyphen)    Keypad -

Keypad , (comma)    Keypad ,

Keypad 0 to 9    Keypad 0 to 9

¡, », ¼, «    CTRL-Keypad ¡, », ¼, «

PF1 to PF4    F1 to F4

NOTE:  "Keypad" refers to the numbers and characters on the
right-hand side of your keyboard.


For Extended Keyboards:
¡, », ¼, «    Grey ¡, », ¼, «

*See Chapter 3, "More About Managing Sessions," and Chapter 7,
"Installation and Configuration," for information on how to
switch the designations of these keys.


Multiple Sessions

Opening Multiple Initial
Sessions
When you first run NCSA Telnet, you can start up multiple
sessions with a single command.

C:\> telnet machinename [machinename ...]

where machinename is the name of the machine you want to
connect to. For example, if you enter telnet yoyodyne you would
be connecting to the machine named yoyodyne.

To start up multiple sessions, enter the additional machinenames
on the same line. Even if you do not choose multiple sessions when
you first run NCSA Telnet, you can add sessions later.


Using the Status Line
Because only 24 lines are needed for VT100 terminal emulation,
line 25 on your PC screen is used to indicate the connection status
of your terminal sessions. For each host you are connected to, a
session name appears in reverse video. The name in the lower-left
corner of the screen is the current session. Beside each name is a
status box that indicates various attributes of a session:

gray    Connection is established, waiting
small box    Active connection, always in lower left corner
*    Connection pending, trying to connect to host
/ or \    Text has been written to this invisible session

Flags appear in the lower-right corner if you are either in the
Scrollback mode or have a capture file open. If you are
transferring files, the FTP status appears in the lower-right corner
as well.  Finally, a clock appears in the lower-right corner if you
enable the clock mode.


Opening Additional
Sessions
When you've initially opened a connection to a single host, you
can open a second connection, to that host or a different one, by
pressing ALT-A (A for add). NCSA Telnet responds by prompting
you for the name of a computer to which it should attempt a
connection.

Indicating the Host
NCSA Telnet can only communicate with host computers that have
IP addresses. You or the NCSA Telnet program can look up IP
addresses in several different ways.

1.    Use any name that is in the configuration file. (Your system
administrator can tell you the names listed there.)
2.    Your system administrator can configure NCSA Telnet to use
the domain-based nameserver to look up host names. Any name
that can be resolved by the domain nameserver can be used. An
example is sri-nic.arpa.

3.    Use the full IP number of the machine, in decimal, separated by
periods, such as 192.17.22.20.If the machine is on the same
Ethernet,

4.     If the machine is on the same Ethernet, enter a pound sign (#),
followed by the host number it uses on your Ethernet. The host
number the machine determined by the class of addressing and
the subnet mask (which your system administrator can
determine for you). For example, if your PC is host
192.17.22.20, you can access host 192.17.22.30 by entering
#30 for the host address.

NCSA Telnet allows you to specify which port number (on the host)
you are connecting to. When you enter the host number, enter a #
symbol right after the IP number, then enter the port number you
wish to connect to. For example, if you enter 141.142.221.17#2000,
this command connects you to the machine 141.142.221.17, port
number 2000.


Estimating the Host
Response Time
NCSA Telnet attempts to make a login connection with the named
host. Usually the connection is instanta-neous, and the host
machine prompts you for a login name immediately. However, the
connection attempt may take several seconds. Even after NCSA
Telnet completes the connection, it may take additional time (up to
two minutes) to prompt you for a login name if a remote host is
heavily loaded.

When the connection is established, the asterisk (*) in the status
box for the connection disappears or changes to a small box. If
NCSA Telnet makes the connection, but the remote host does not let
you log in, you may want to press ALT-X to end the connection.


Using Scrollback Mode
The SCROLL LOCK key performs two functions. It prevents the
screen from scrolling when new text arrives, and also puts you
into scrollback mode. In scrollback mode, both the up and down
arrow keys and PG UP and PG DN keys scroll the screen
backwards and forwards. When you press the SCROLL LOCK key
again, it ends scrollback mode and resets the working area of the
screen.

The number of lines the program saves is limited by the amount of
memory in your machine and its setting in the configuration file.
If your PC runs out of memory, or the specified number of lines
have already been stored, NCSA Telnet starts dropping the lines at
the top of the scrollback as you add new lines to the bottom.

NOTE:  No other commands work while you are using scrollback
mode.


Using the Cut and Paste
Functions
The cut and paste functions allow you to copy blocks of text from
one session to another, or within the same session. To use these
functions, follow these steps:

1.    Enter Scrollback mode via Scrl_Lock or the right mouse button.

2.    Move the cursor to the beginning position of the text you wish to
copy, and press the space bar.

3.    Move the cursor to the end of the text and press the space bar
again. This action selects the area to copy.

4.    Press ALT-C while still in scrollback mode. This action copies
the text into a buffer.

5.    Exit Scrollback mode, and switch sessions by pressing ALT-N
or ALT-B, if you desire.

6.    Position the cursor where you wish to insert the text, and press
ALT-V. This action inserts the text at the current position as if
you had typed it in.

You can use the copy and paste functions without touching the
keyboard if you have a Microsoft-compatible mouse attached and
driver loaded.

1.    Press the right mouse button to enter Scrollback mode.

2.    Scroll to the beginning of the text you wish to copy, and press the
left mouse button.

3.    Move the cursor to the end of the text, and press the left mouse
button again.

4.    Press and hold the left mouse button, press the right mouse
button, then release both buttons. This action copies the text into
the buffer.

5.    Exit Scrollback mode by pressing the right mouse button.

To paste the buffer to the screen, press and hold the right mouse
button, then press the left mouse button, then release them both. The
text should appear as if you typed it in.


Switching Between
Sessions (ALT-N)
The status line at the bottom of the screen indicates the active telnet
sessions. To rotate to the next session, press ALT-N (for next).
This action makes the next session the current one and moves its
name to the lower left corner of the screen. Any characters you now
type on the keyboard are sent to this, the current session.

To move back one session, press ALT-B (for back).


Displaying Console
Messages (ALT-Z)
In the process of connecting and communicating with other hosts
via TCP/IP, NCSA Telnet provides you with information on the
console (message) screen. To see this screen, press ALT-Z. Your
sessions are still running; however, you cannot see them. When
you have viewed the messages, press any key to return to your
session. The information on the console screen can tell you about
errors, warnings, FTP access to your PC, and network conditions
that may be of concern to network administrators.


Exiting the Present
Connection (ALT-X)
To close the current session, press ALT-X. A dialog box appears
prompting you to confirm that the connection should be closed.
Once confirmed, the connection shuts down.  The close may take
several seconds to complete.

NOTE:  You can press ALT-X to log out of a host as well as
terminate a given session, but the command bypasses normal
conventions and may cause problems for the host. The correct way
to close a connection with a host is to log out of the host using the
normal logout procedure for that host.


Capture File Operations

Text that appears on the screen can be captured and sent to a file or
the local printer. When you press ALT-C, capture is turned on.
Pressing ALT-C again toggles capture off. Any text that appears on
the screen is captured and appended to the capture file. NCSA
Telnet never erases the capture file, only appends text to it. The
default capture file is named capfile, but you can change that, as
discussed in the next session.


Designating a Capture File
You can designate a different capture file by using the Parameter
menu. When you press ALT-P the Parameter menu appears. (Most
of the Parameter menu choices are discussed in Chapter 3, "More
About Managing Sessions.") Use the arrow keys to select the
Parameter menu entry for the capture filename. Press RETURN
to clear the current entry and then enter your new filename. After
you've changed the name of the capture file, all subsequent ALT-C
commands will use the new capture file. You can also change the
name of the capture file "permanently" in the configuration file
(see Chapter 6, "Installation and Configuration.").


Using PRN
If you want to send all captured text directly to a local printer,
follow the directions above for naming new filenames. Enter prn
as the new filename. This name is the default filename for
printing in the NCSA Telnet program. PC-DOS reserves this
filename for the printer.

A common problem can occur while you are capturing files to the
printer that can cause NCSA Telnet to abort. If the printer is off-
line or out of paper when a capture begins, the message:

Error, A(bort) R(etry) or I(gnore)?

appears on the screen. For the former problem, turn the printer on
and off and then press R for retry. Do not press A at this point
because it will abort NCSA Telnet and cut off all of your network
connections.


Using One Capture at a
Time
You can capture text to a file or the printer in any session, but not
for more than one session at a time. When a capture is active for a
session in the background, you cannot invoke capture on the
current session. If you attempt to do so, you will not get the
confirmation message on line 25 and NCSA Telnet reminds you of
the error. The capture procedure will continue to capture all text for
the background session while you interact with the current
session.

If you press ALT-D, NCSA Telnet dumps the contents of the current
session screen into the capture file if one is not already open. If a
capture file is open, nothing happens when you press ALT-D.

NOTE:  If you press ALT-D, NCSA Telnet dumps only the contents
of the current session screen into the capture file. If you press ALT-
C, however, NCSA dumps everything from your current session
into the capture file.