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HP TCP/IP Services for OpenVMS

HP TCP/IP Services for OpenVMS
User's Guide
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A user sends the cat command to host magic . /PASSWORD invokes REXEC, which requires a password. Because the password was omitted from the command line, REXEC prompts the user for it.

Chapter 4
Establishing Network Terminal Sessions Using TELNET/TN3270

With the TELNET software in TCP/IP Services, you can log in to a remote internet system. This is called establishing a TELNET session. Your terminal appears to be attached directly to the remote system.

You can establish a TELNET session with a host that uses IBM 3270 model terminals (TN3270).

Note that you can also use RLOGIN to log in to remote internet hosts. However, RLOGIN does not have the ability to manage a 3270 session. To determine the best remote login service for your needs, see Section 1.1.2. For more information about RLOGIN, see Chapter 3.

The following table lists the TELNET/TN3270 network terminal services and the sections that explain how to use them.
Capability Section
Use either DCL or UNIX command syntax. 4.1
Establish a network terminal session with any other host that uses TCP/IP as a transport. 4.3
Log all terminal output to a file. 4.5
Toggle between the remote host and the local TELNET prompt. 4.7
Suspend TELNET/TN3270 to spawn a subprocess at the DCL prompt. 4.8
Establish multiple TELNET sessions. 4.9
Toggle between open sessions. 4.9.1
Customize the way TELNET interprets control characters, sends and receives transmissions, and displays processing on your terminal. 4.6.2
4.10
Send commands to the remote host that affect processing of commands you have entered. 4.11
Run IBM 3270 model terminal emulation (TN3270). 4.12
Record a TN3270 screen's contents. 4.12.5

To use the network terminal services, you need the following:

To use TELNET, enter the commands summarized in Table 4-1. (For complete command descriptions, see Section 4.13.)

Table 4-1 TELNET/TN3270 Commands Summary
DCL Style UNIX Style Description
Starting (at the DCL Prompt)
TELNET telnet Invokes TELNET.
TELNET remote_host telnet remote_host Invokes TELNET and establishes a connection to a remote host.
TN3270 N/A Invokes TELNET and TN3270.
TN3270 remote_host N/A Invokes TELNET, runs TN3270, and establishes a connection to a remote host.
Getting In and Out of Sessions
CONNECT open Establishes a connection between the local host and a remote host.
CREATE_SESSION N/A Establishes a pseudo device and connects it to a remote listener port.
DELETE_SESSION N/A Deletes a pseudo device created by the CREATE_SESSION command.
DISCONNECT close Terminates your current session.
Ctrl/] Ctrl/] Takes you from the remote host back to the TELNET prompt.
EXIT quit Closes open connections and exits from TELNET.
HELP help
? 		Invokes online help.
RESUME [Return] Resumes an open connection.
SPAWN z Suspends your TELNET session and takes you to the DCL prompt.
 
Customizing the TELNET Environment
DISABLE AUTOFLUSH toggle autoflush Disables the automatic flushing of output when interrupt characters are sent.
DISABLE AUTOSYNCH toggle autosynch Disables the automatic sending of interrupt characters in urgent mode.
DISABLE BINARY toggle binary Disables transmission in binary mode.
DISABLE CRLF toggle crlf Disables the sending of carriage returns as Return LF.
DISABLE CRMOD toggle crmod Disables the mapping of received carriage returns.
DISABLE DEBUG toggle netdata Disables the display of data flow information in hexadecimal.
DISABLE
LOCAL_CHARS 		toggle localchars Disables the interpretation of certain control characters by your local TELNET client and passes them to the remote TELNET server.
DISABLE
OPTIONS_VIEW 		toggle options Disables the display of option negotiations between the client and server.
ENABLE AUTOFLUSH toggle autoflush Enables the automatic flushing of output when interrupt characters are sent.
ENABLE AUTOSYNCH toggle autosynch Enables the automatic sending of interrupt characters in urgent mode.
ENABLE BINARY toggle binary Enables transmission in binary mode.
ENABLE CRLF toggle crlf Enables the sending of carriage returns as Return LF.
ENABLE CRMOD toggle crmod Enables the mapping of received carriage returns.
ENABLE DEBUG toggle netdata Enables the display of data flow information in hexadecimal.
ENABLE
LOCAL_CHARS 		toggle localchars Enables the interpretation of certain control characters by your local TELNET client and prohibits them from being passed to the remote TELNET server.
ENABLE
OPTIONS_VIEW 		toggle options Enables the display of option negotiations between the client and server.
SHOW DEVICE Displays the current devices.
SHOW PARAMETERS display Displays the current parameter settings.
SHOW SESSION Displays the current sessions.
SHOW STATUS status Displays the current status.
SET ECHO set echo Sets the echo character to the specified character.
SET ERASE set erase Sets the erase character to the specified character.
SET ESCAPE set escape Sets the escape character to the specified character.
SET
FLUSHOUTPUT 		set flushoutput Sets the flush output character to the specified character.
SET INTERRUPT set interrupt Sets the interrupt character to the specified character.
SET KILL set kill Sets the kill character to the specified character.
SET MODE mode Sets the transmission mode to character or line.
SET QUIT set quit Sets the quit character (an alternate interrupt character) to the specified character.
SET TERMINAL   Sets the terminal type to the specified model.
Sending Commands to the Remote Host
SEND AO send ao Sends the Abort Output command.
SEND AYT send ayt Sends the Are You There command, testing the path to the remote application and eliciting connection status information from the remote host.
SEND BRK send brk Sends the Break command.
SEND EC send ec Sends the Erase Character command.
SEND EL send el Sends the Erase Line command.
SEND GA send ga Sends the Go Ahead command.
SEND IP send ip Sends the Interrupt character.
SEND NOP send nop Sends the No Operation command to test whether data can be sent to the remote host, eliciting an error if the connection is not open.
SEND SYNCH send synch Sends the Synchronize character.

4.1 Typing TELNET/TN3270 Commands

Use the following rules when you enter a TELNET command line.

4.1.1 DCL and UNIX Command Formats

With the TELNET command and most of the commands entered at the TELNET prompt, you can use either DCL or UNIX syntax. For example, the following two commands produce the same results: 


$ TELNET 
TELNET> SHOW PARAMETERS 



$ TELNET 
TELNET> DISPLAY

4.1.2 Quotation Marks

Do not include quotation marks on the command line, as shown in the following examples:

The following example connects to UNIX host migain and sets a terminal type with the /TERMINAL_TYPE qualifier. No quotation marks are needed to pass a terminal type to migain in lowercase, as demonstrated with the remote host's printenv command. 


$ TELNET MIGAIN /TERMINAL_TYPE=vt300 
%TELNET-I-Trying, Trying ...11.90.208.56 
%TELNET-I-SESSION, Session 01, host migain, port 23 
-TELNET-I-Escape, Escape character is '^]' 
 
Hello from UNIX host migain 
 
login: root 
Password:... 
   .
   .
   .
migain#  printenv 
 
TERM=vt300 
HOME=/ 
SHELL=/bin/csh 
USER=root 
PATH=/bin:/usr/bin:/usr/ucb:/etc:/usr/etc:. 
LOGNAME=root 
PWD=/ 
migain#

4.2 Obtaining Online Help

You can obtain online help for the TELNET and TN3270 services by entering any of the following commands at the DCL prompt: 


$ HELP TELNET 
$ HELP TN3270 
$ HELP TCPIP_SERVICES TELNET

You can also enter the HELP command at the TELNET prompt: 


TELNET> HELP

4.3 Starting TELNET and TN3270

You can start a TELNET or TN3270 session with a remote host (also called establishing a connection and opening a connection) in one of the following ways:

The following example shows three ways to establish a connection interactively: 


$ TELNET CENTRAL /TERMINAL_TYPE=IBM-3278-2 
 
$ TELNET 
TELNET> CONNECT CENTRAL 23 VT200 
 
$ TN3270 CENTRAL /TERMINAL_TYPE=IBM-3278-3

You can invoke TELNET or TN3270 and, without connecting to a remote host first, enter certain commands that customize the sessions and display parameters or status, as shown in the following example: 


$ TELNET 
TELNET> SHOW STATUS 
%TELNET-E-NOSESSION, No active session 
Escape character: '^]' 
TELNET>SET DEVICE TERMINAL=VT300 
TELNET> OPEN GALAXY 
%TELNET-I-TRYING, Trying ... 1.20.208.10 
%TELNET-I-SESSION, Session 01, host galaxy, port 23 
-TELNET-I-ESCAPE, Escape character is ^] 
 
Compaq Tru64 UNIX (galaxy.udb.com) (ttyp5) 
 
login:

4.3.1 Establishing Kerberos-Based Secure Connections

Kerberos is a network authentication protocol designed to provide strong authentication for client/server applications by using secret-key cryptography. Kerberos uses strong cryptography so that a client can prove its identity to a server (and vice versa) across an insecure network connection. The TCP/IP TELNET service uses Kerberos to make sure the identity of any user who requests access to a remote host is authentic.

Before you can use the Kerberos TELNET client, the OpenVMS Security Client software must be configured on the OpenVMS system. For more information about installing and configuring the OpenVMS Security Client software, see the OpenVMS Alpha Version 7.3-2 Upgrade and Installation Manual.

4.3.1.1 Kerberos Principal Names

Before you use the Kerberos TELNET client, make sure the local host name is fully qualified in the local hosts database. Kerberos realms form principal names using fully-qualified domain names. For example, terse.mbs.com is a fully qualified domain name; terse is a simple host name.

HP TCP/IP Services for OpenVMS is usually configured so that the host name is entered in the hosts database as a simple host name. That is, on host TERSE, the TCP/IP management command SHOW HOST TERSE returns terse , not terse.mbs.com .

To correct a mismatch between the Kerberos realm and the TCP/IP Services configurations, follow these steps from a privileged account at a time when system usage is low:

  1. Find the host's numeric address. For example: 


    $ TCPIP 
TCPIP> SHOW HOST terse 
       
     LOCAL database 
  
Host address    Host name 
 
15.28.311.11   terse

  2. Remove the simple host name. For example: 


    TCPIP> SET NOHOST terse/CONFIRM

  3. Use the SET HOST command to associate the fully qualified domain name with the IP address, as shown in the following example: 


    TCPIP> SET host "terse.mbs.com"/ADDRESS=15.28.311.11 - 
_TCPIP> /ALIAS=("TERSE.MBS.COM", "terse", "TERSE")

    Specify the /ALIAS qualifier to ensure that applications can handle host names in uppercase and lowercase.

  4. Confirm that the first name returned is fully qualified. 


    TCPIP> SHOW HOST terse 
       
     LOCAL database 
  
Host address    Host name 
 
15.28.311.11   terse.mbs.com, TERSE.MBS.COM, terse, TERSE

4.3.1.2 Initiating an Authenticated TELNET Connection

To initiate an authenticated connection, perform the following steps:

  1. On a Kerberos-enabled system, enter a KINIT username command. Enter your password when prompted.

    Note
    Always specify the user name on the KINIT command line. Kerberos realms are usually set up with lowercase user names, but on OpenVMS, user names are stored in uppercase. When you specify the user name, it will be accepted as lowercase.
  2. To initiate an authenticated connection, enter the following command: 


    $ TELNET/AUTHENTICATE host-name

  3. To use the same ticket on a remote system, you can forward your ticket by entering the following command: 


    $ TELNET/AUTHENTICATE/FORWARD host-name

  4. To use your credentials in another realm, enter the following command: 


    $ TELNET/AUTHENTICATE/REALM=realm-name.

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