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This chapter describes how to connect a client terminal or microcomputer running terminal-emulation software such as Telnet, rlogin, TN3270, and Local Area Transport (LAT) through one of our server products to a host across a LAN or WAN. Specifically, this chapter contains the following sections:
Digital Equipment Corporation's (Digital's) Local Area Transport (LAT) protocol is most often used to connect servers to Digital hosts. LAT is a Digital-proprietary protocol, and your server uses LAT technology licensed from Digital. You can perform the following LAT connection tasks:
These tasks are described in the following sections.
To connect to a LAT host, enter the lat EXEC command at the system prompt. The lat command has the following syntax:
lat name [node nodename | port portname | /debug]| name | Your LAT-learned service name. |
| node nodename | (Optional) Specifies a connection to a particular LAT node that offers a service. If you do not include the node option, the node with the highest rating offering the service is used. Use the EXEC command show lat nodes to display information about all known LAT nodes. |
| port portname | (Optional) Specifies a destination LAT port name. This keyword is ignored in most timesharing systems, but is used by servers offering reverse LAT services. Reverse LAT involves connecting to one server from another. In this case, the target server runs the host portion of the protocol. Enter the port name in the format of the remote system in place of the portname argument. |
| /debug | (Optional) A switch that, when enabled, prints parameter changes and other special messages on the screen. |
You can quit the connection by entering Ctrl-C, or complete the connection by entering the password for a given service.
If your preferred transport is set to lat, you can use the connect command in place of the lat command. Refer to the Access and Communication Server Configuration Guide for more information about configuring a preferred transport type. When your preferred transport is set to none or to another protocol, you must use the lat command to connect to a LAT host.
The following example establishes a LAT connection from the server named cs to host eng2:
cs> lat eng2
Trying ENG2...Open
ENG2 - VAX/VMS V5.2
Username: JSmith
Password:
Welcome to VAX/VMS version V5.2 on node ENG2
Last interactive login on Friday, 1-APR-1994 19:46
The system informs you of its progress by displaying the messages "Trying <system>..." and then "Open." If the connection attempt is not successful, you receive a failure message.
The following example establishes a LAT connection from the server named cs to our-modems and specifies port 24, which is a special modem:
cs> lat our-modems port 24
The following example establishes a LAT connection from the server named cs to our-modems and specifies a node named eng:
cs> lat our-modems node eng
The following example uses the LAT session debugging capability:
cs> lat Eng2 /debug
Trying ENG2...Open
ENG2 - VAX/VMS V5.2
Username: JSmith
Password:
Welcome to VAX/VMS version V5.2 on node ENG2
Last interactive login on Tuesday, 5-APR-1994 19:02
[Set Flow out off, Flow in on, Format 8:none, Speed 9600/9600]
[Set Flow out off, Flow in on, Format 8:none, Speed 9600/9600]
$ set ter/speed=2400
[Set Flow out off, Flow in on, Format 8:none, Speed 2400/2400]
A variety of LAT events are reported, including all requests by the remote system to set local line parameters. The messages within brackets ([ ]) above are the messages produced by the remote system setting line characteristics to operating system defaults.
You can temporarily define the list of services to which you or another user can connect. You do this by defining the group code lists used for connections from specific lines.
You limit the connection choices for an individual line by defining the group code lists for an outgoing connection. When a user initiates a connection with a LAT host, the user's line must share a common group number with the remote LAT host before a connection can be made.
The group code range entered must be a subset of the line's configured group code range. Use the following command:
terminal lat out-group {groupname | number | range}| groupname | Name of the group that has access to the system through the specified line. |
| number | Number of the group that has access to the system through the specified line. |
| range | The range of group numbers. Separate the beginning and end of the range with a hyphen. |
The group code range entered in this command must fall within the group code range already configured for the line.
cs> terminal lat out-group 4, 6-189
You can have several concurrent LAT sessions open and switch back and forth between them.
To open a subsequent session, first enter the escape sequence (Ctrl-^ X) to quit the current session. Then open a new session.
To list the available LAT services, issue the following command:
show lat servicesFor sample output to this command, and for information about switching between LAT sessions, refer to the chapter "Monitoring and Managing Connections" later in this publication.
Your server supports a subset of Digital commands, including the following:
| Task | Command |
|---|---|
| List EXEC commands. | help |
| Close the active session. | logout |
You can issue any of the following commands to terminate an active LAT session:
exitTwo Transmission Control Protocol/Internet Protocols (TCP/IP), Telnet and rlogin, are available for making connections to a host.
Telnet, a virtual terminal protocol that is part of the TCP/IP protocol suite, allows for connections to hosts. Telnet is the more widely used protocol.
The rlogin protocol is a remote login service developed for the BSD UNIX system. It provides better control and output suppression than Telnet, but can only be used when the host (typically, a UNIX system) supports rlogin. Our implementation of rlogin does not subscribe to the trusted host model. That is, a user cannot automatically log on to a UNIX system from the server, but must provide a user ID and a password for each connection.
This implementation of Telnet and rlogin provides these connection capabilities:
These tasks are described in the following sections.
To log on to a host that supports Telnet, enter one of the following commands:
connect host [port] [keyword] telnet host [port] [keyword]| host | A host name or an Internet address. |
| port | (Optional) A decimal TCP port number; the default is the Telnet server port (decimal 23) on the host. |
| keyword | (Optional) One of the options listed in Table 3-1. |
| Option | Description |
|---|---|
| /route path | Specifies loose source routing. The path argument is a list of host names or Internet addresses that specify network nodes, ending with the final destination. |
| /line | Enables Telnet line mode. In this mode, the server sends no data to the host until you press Return. You can edit the line using the standard server command editing characters. The /line keyword is a local switch; the remote server is not notified of the mode change. |
| /debug | Enables Telnet debugging mode. |
| /stream | Turns on stream processing, which enables a raw TCP stream with no Telnet control sequences. A stream connection does not process Telnet options, and can be appropriate for connections to ports running UUCP and other non-Telnet protocols. |
With the Cisco implementation of TCP/IP, you are not required to enter the connect or telnet commands to establish a Telnet connection. You can just enter the learned host name--as long as the host name is different from a command word for the server.
To display a list of the available hosts, enter the following command:
show hostsTo display the status of all TCP connections, enter the following command:
show tcpThe server assigns a logical name to each connection and several commands use these names to identify connections. The logical name is the same as the host name, unless that name is already in use, or you change the connection name with the EXEC command name-connection. If the name is already in use, the server assigns a null name to the connection.
The following example routes packets from the source system to kl.sri.com, then to 10.1.0.11, and finally to mathom:
cs> connect mathom /route:kl.sri.com 10.1.0.11 mathom
The following example connects to a host with logical name mathom:
cs> mathom
The Telnet software supports special Telnet commands in the form of Telnet sequences that map generic terminal control functions to operating system-specific functions.
To issue a special Telnet command, enter the escape sequence and then a command character. The default escape sequence is Ctrl-^ (press and hold the Control and Shift keys while pressing the 6 key). You can enter the command character as you hold down Ctrl or with Ctrl released; you can type either uppercase or lowercase letters.
Table 3-2 lists the special Telnet commands.
| Task | Escape Sequence |
|---|---|
| Break | Ctrl-^ B |
| Interrupt Process (IP) | Ctrl-^ C |
| Erase Character (EC) | Ctrl-^ H |
| Abort Output (AO) | Ctrl-^ O |
| Are You There? (AYT) | Ctrl-^ T |
| Erase Line (EL) | Ctrl-^ U |
At any time during an active Telnet session, you can list the Telnet commands by entering the escape sequence followed by a question mark at the system prompt:
Ctrl-^ ?A sample of this list follows.
cs> ^^?
[Special telnet escape help]
^^B sends telnet BREAK
^^C sends telnet IP
^^H sends telnet EC
^^O sends telnet AO
^^T sends telnet AYT
^^U sends telnet EL
You can have several concurrent rlogin connections open and switch back and forth between them.
To open a new connection, exit out of the current connection by typing the escape sequence
(Ctrl-^ X), to return to the system command prompt, then open a new connection.
To log on to a UNIX host using rlogin, enter the following command:
rlogin host [debug]| host | Specifies the host name or Internet address. |
| debug | (Optional) Enables debugging output from the rlogin protocol. |
The following example makes an rlogin connection to a host at address 108.33.21.2 and enables the message mode for debugging:
cs> rlogin 108.33.21.2 debug
You can have several concurrent sessions open and switch back and forth between them. The number of sessions that can be open is defined by the session-limit command, which is described in the publications Access and Communication Servers Configuration Guide and Access and Communication Servers Command Reference.
You can switch between sessions by escaping one session and resuming a previously opened session, as follows:
Step 1 Escape out the current session by pressing Ctrl-^ X and return to the EXEC prompt.
Step 2 List the open sessions using the where command. All open sessions associated with the current terminal line are displayed.
Step 3 Type the resume command and the session number to make the connection.
You can also resume the previous session by pressing the Return key.
The where command has no additional syntax. The resume command has the following syntax when used on the server:
resume [connection] [keyword]| connection | (Optional) The name or number of the connection; the default is the most recent connection. |
| keyword | (Optional) One of the options listed in Table 3-3. |
| Option | Description |
|---|---|
| /debug | Prints parameter changes and messages. On a server, this option displays informational messages whenever the remote host changes an X.3 parameter or sends an X.29 control packet. |
| /echo | Performs local echo. |
| /line | Enables line-mode editing. |
| /nodebug | Cancels printing of parameter changes and messages. |
| /noecho | Disables local echo. |
| /noline | Disables line mode and enables character-at-a-time mode, which is the default. |
| /nostream | Disables stream processing. |
| /set parameter:value | Sets X.3 connection options. Refer to the "X.3 PAD Connections" section in the "Terminal or Telecommuting Service Connections Using Protocol Translation" chapter for a list of these connection options. |
| /stream | Enables stream processing. |
The Ctrl-^-X, where, and resume commands are available with all supported connection protocols.
The following example shows how to escape out of a connection to the host Swift and to resume connection 2:
Swift% ^^X resume 2
You can omit the command name and simply type the connection number to resume that connection. The following example illustrates how to resume connection 3:
cs> 3
You can issue any of the following commands to terminate an active Telnet or rlogin session:
exitYou use TN3270 terminal emulation to connect to an IBM host . Your system administrator must configure a default terminal emulation file that permits the terminal to communicate correctly with the host. Refer to the publications Access and Communication Servers Configuration Guide and Access and Communication Servers Command Reference to specify alternate terminal emulations. Your administrator can also specify custom terminal emulations.
Unlike Telnet and LAT connections, you must enter the command tn3270 to make a connection to an IBM 3278 host. To begin a TN3270 session, enter the following command:
tn3270 hostname| hostname | Name of a specific host on a network that can be reached by the server. The default terminal emulation mode allows access using a VT100 emulation. |
The following example establishes a terminal session with an IBM host named "finance:"
cs> tn3270 finance
To terminate an active TN3270 session, you can issue any of the following commands:
exit
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