P200 [7] and 7800 [8] VIP (Visual Information Projection) terminals
differ mainly from NVT terminals [1] in that they work in block mode
and have the capability to manage an associated printer. Generally in
a DSA (Distributed Systems Architecture) network they are managed
through the VIP transmission line procedure (character oriented).
That is the reason why they are generically referred as VIP
terminals.
This document specifies the options to be modified successfully, to
pass from the NVT terminal emulation supported on a Telnet
connection, to a VIP terminal emulation. It defines also the format
of the messages exchanged between the server and the client when the
TNVIP protocol is successfully negotiated.
Dujonc Informational [Page 2]
RFC 1921 TNVIP Protocol March 1996
VIP terminal family includes a broad range of different terminal
types. They work in block mode with an ASCII or 8 binary bits set of
characters.
The Bull terminals in the DSA network environment use the services of
a Terminal Manager (TM) [2]. It is generally installed in a
communication processor (as a Datanet or Mainway system) where it
assures the connection with the BULL host application generally
through a DSA session.
The Terminal Manager is in charge to present the terminal station and
to manage the session connection to the host computer. It offers
generally a possibility of dialog with the terminal to allow the user
to modify the connection parameters, to manage the session
(connection request, abort, etc ..). The set of commands and
responses used is called "TM Local Dialog".
The mandatory telnet parameters to be negotiated successfully between
the "TNVIP server" and the "TNVIP client" are :
- the Terminal-Type option [3] to define a VIP terminal model and
if necessary a Mailbox name to request a specific access point in
the "TNVIP server",
- the End Of Record option [4] to delimit the TNVIP message at the
Telnet level. As the End Of Record (EOR) code indicates the end of
an effective data unit, Telnet should attempt to send the data up
to and including the EOR code together to promote communication
efficiency.
Others Telnet parameters, can be optionally negotiated as :
- the Binary Transmission option [5], when the terminal emulation
uses a 8 binary bits set of characters,
- the Suppress Go Ahead option [6], when no synchronisation of the
data transmission from the "TNVIP client" with the DSA session
turn or the ISO session token is needed.
When the two parties (the "TNVIP server" and the "TNVIP client") have
negotiated successfully a TNVIP terminal type and the EOR telnet
option, that means they agree to respect the TNVIP protocol (the
TNVIP message format and the exchange rules).
Dujonc Informational [Page 3]
RFC 1921 TNVIP Protocol March 1996
IAC DO TERMINAL-TYPE
Sender (the "TNVIP server" party) is willing to receive terminal
type information in a subsequent sub-negotiation.
IAC WILL TERMINAL-TYPE
Sender (the terminal "TNVIP client" party) is willing to send
terminal-type information in a subsequent sub-negotiation.
IAC SB TERMINAL-TYPE SEND IAC SE
Sender (the "TNVIP server" party) requests the receiver to
transmit his next terminal-type, and switch emulation modes (if
more than one terminal type is supported).
IAC SB TERMINAL-TYPE IS tnvip-terminal-model@MB-name IAC SE
Sender (the terminal "TNVIP client" party) is stating the name of
his current (or only) terminal-type. Optionally, a mailbox name
can be added to request a particular access point in the "TNVIP
server". By default, the "TNVIP server" uses a generic access
point.
The TNVIP terminal type string given at the Telnet negotiation is
formatted as follows :
<TNVIP-terminal-model> [ <@ character> <Mailbox-name> ]
The @ character is used as separator between the VIP-terminal-model
and the Mailbox-name.
Dujonc Informational [Page 4]
RFC 1921 TNVIP Protocol March 1996
The valid TNVIP terminal models are the following ASCII character
strings. (The table gives for each terminal model string the
hexadecimal number indicating the associated DSA model number defined
in the DSA terminal presentation protocols ).
P200 family 7800 family
-------------------------------- --------------------------------
! TNVIP model ! DSA code ! ! TNVIP model ! DSA code !
-------------------------------- --------------------------------
! VIP7700 ! 33 ! ! VIP7804 ! 3E !
! VIP7760 ! 3A ! ! VIP7804V ! 4A !
! DKU7005 ! 3D ! ! VIP7814 ! 47 !
! DKU7007D ! 40 ! ! HDS7 ! 4D !
! DKU7105 ! 41 ! ! VIP8800 ! 4F !
! DKU7107D ! 42 ! --------------------------------
! DKU7211 ! 45 !
! DKU7211D ! 4E !
--------------------------------
The D character at the end of the string indicates that the terminal
supports the Remote Forms function [9]. It is the capability to store
forms in the terminal allowing the host application to display a form
stored in the terminal sending a short length command without sending
all the data of the form. This function is usually supported by the
terminal concentrators.
The mailbox name allows the "TNVIP client" to request a specialized
access point referenced by this name in the "TNVIP server". It is an
ASCII character string. Its presence in the Telnet terminal type
string is optional. When not present, a generic (default) access can
be provided by the "TNVIP server".
When the "TNVIP server" is a gateway to DSA hosts, the mailbox name
defines the DSA session access point of the terminal in the server.
Its length is limited to 12 characters. Lower case characters are
allowed but are processed as upper case. This string is generally
used to identify a specific terminal station (having a printer for
example) or to use a particular declaration of this terminal in the
"TNVIP server".
Dujonc Informational [Page 5]
RFC 1921 TNVIP Protocol March 1996
VIP device communications are block oriented. That is, each partner
buffers data until an entire "message" has been built, at which point
the data are sent to the other side. The end of a message is
understood to be the last byte transmitted. The Telnet EOR command is
used to delimit these natural blocks of TNVIP data within the Telnet
data stream. An <EOR> is sent at the end of each TNVIP message, in
both directions.
IAC WILL END-OF-RECORD
The sender of this command requests permission to begin
transmission of the Telnet END-OF-RECORD (EOR) code when
transmitting data characters, or the sender of this command
confirms it will now begin transmission of EORs with transmitted
data characters.
IAC DO END-OF-RECORD
The sender of this command requests that the sender of data starts
transmitting the EOR code when transmitting data, or the sender of
this command confirms that the sender of data is expected to
transmit EORs.
According to the character set used by the emulation, the "TNVIP
client" and the "TNVIP server" can be led to negotiate the Telnet
binary transmission option.
If either side wishes to transmit the decimal value 255 and have it
interpreted as data, it must "double" this byte. In other words, a
single occurrence of decimal 255 will be interpreted by the other
side as an IAC, while two successive bytes containing decimal 255
will be treated as one data byte with a value of decimal 255.
IAC DO TRANSMIT-BINARY
Sender requests that sender of the data starts transmitting or
confirms that the sender of data is expected to transmit
characters that are to be interpreted as 8 bits of binary data by
the receiver.
IAC WILL TRANSMIT-BINARY
Sender requests permission to begin transmitting, or confirms it
will now begin transmitting binary data.
Dujonc Informational [Page 6]
RFC 1921 TNVIP Protocol March 1996
IAC WON'T TRANSMIT-BINARY
If the connection is already being operated in binary transmission
mode, the sender of this command demands to begin transmitting
data characters which are to be interpreted as standard NVT ASCII
characters by the receiver of the data. If the connection is not
already being operated in binary transmission mode, the sender of
this command refuses to begin transmitting characters which are to
be interpreted as binary characters by the receiver of the data
(i.e., the sender of the data requests to continue transmitting
characters in its present mode).
IAC DON'T TRANSMIT-BINARY
If the connection is already being operated in binary transmission
mode, the sender of this command requests that the sender of the
data start transmitting characters which are to be interpreted as
standard NVT ASCII characters by the receiver of the data
(i.e.,the party sending this command). If the connection is not
already being operated in binary transmission mode, the sender of
this command requests that the sender of data continue
transmitting characters which are to be interpreted in the present
mode.
The "TNVIP client" can use the receiving of the Telnet GoAhead
command as the signal allowing the terminal operator to transmit
data. That can allow the synchronisation between the data transmitted
from the terminal and the DSA "turn".
When the Suppress Go Ahead option is not negotiated, the "TNVIP
server" must send the Telnet Go Ahead command (GA) when its input
message queue (from the "TNVIP client") is empty and the DSA turn is
at the terminal side, to invite the terminal to transmit some data.
To suppress this mechanism, the "TNVIP client" can request the no
sending of the Telnet GoAhead commands by the "TNVIP server",
negotiating the Suppress GO Ahead option of the Telnet Protocol.
In this case, the terminal transmission to the "TNVIP server" is
synchronised on the transport credit.
Note: The Telnet GA command never need to be sent by the "TNVIP
client" even if the telnet Suppress Go Ahead has not been
negotiated.
Dujonc Informational [Page 7]
RFC 1921 TNVIP Protocol March 1996
IAC DO SUPPRESS-GO-AHEAD
The sender of this command (the "TNVIP client" party) requests that
the sender of data starts suppressing GA when transmitting data.
IAC WILL SUPPRESS-GO-AHEAD
The sender of this command (the "TNVIP server" party) confirms it
will now begin suppressing transmission of GAs with transmitted
data characters.
IAC DON'T SUPPRESSS-GO-AHEAD
The sender of this command (the "TNVIP client" party) requests
that the receiver of the command start transmitting GAs when
transmitting data.
IAC WON'T SUPPRESS-GO-AHEAD
The sender of this command (the "TNVIP server" party) confirms it
will now begin transmitting the GA character when transmitting
data characters.
The TNVIP protocol allows the following functions :
- Support of a VIP terminal emulation addressing the screen and its
associated printer .
- Selection of the terminal type model at the connection time.
- Specific or generic access to the "TNVIP server" by referencing or
not a Mailbox name.
- TNVIP protocol independent of the terminal data presentation
protocol (7800 or P200).
- Support of the DSA End To End Acknowledgement.
- Support of the DSA Terminal Manager local attention.
- Support of the DSA turn to the terminal side.
- Support of the DSA secret read.
- Control of the hard copy.
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RFC 1921 TNVIP Protocol March 1996
The "TNVIP client" acts as the interface adapter between the TNVIP
connection and an application program. The "TNVIP client" is mainly
defined to support a VIP terminal emulation program but can be used
by other else program using the TNVIP protocol.
A VIP terminal emulation manages:
- a screen buffer,
- a printer buffer if it supports the associated printer,
- the interface with the communication line
and runs using the following rules:
When the VIP terminal emulation exchanges a message on the
communication line, it is in the BUSY state until the end of the
message exchange. That means when the VIP terminal is sending a
message it can't receive and when it is receiving a message it can't
send.
Note: If a VIP terminal works in the half duplex mode, as the TNVIP
protocol uses a Telnet connection it allows a full duplex
mode processing.
The VIP terminal has the capability to switch between these two
states. The LOCAL state is generally used to process local terminal
tests or to modify the configuration. In this state, the data coming
from the line are ignored.
The LOCAL state allows the "TNVIP client" to request to the server
the screen and printer data flows to be suspended.
The ONLINE state indication allows the "TNVIP server" to resume the
screen and printer flows.
For these reasons the TNVIP protocol differentiates the screen and
printer flows from the screen copy printing flow and defines to
report the two states to the "TNVIP server".
Dujonc Informational [Page 9]
RFC 1921 TNVIP Protocol March 1996
When a VIP terminal emulation receives a data message from the line,
according to the address given in the header message,it sends data to
the screen buffer or to the printer buffer.
A message received at the screen or printer address is deleted and
ignored if the terminal emulation is in the LOCAL state and a BUSY
status is returned.
The printer buffer is busy when the terminal is transmitting the data
from the printer buffer to the printer device. A data message for the
printer is deleted and ignored if the terminal is in the printing
state and a BUSY status is returned.
When a BUSY state is encountered, the "TNVIP client" according to the
type of message received (request or indication) reports or not the
BUSY acknowledgement to the "TNVIP server".
Its function is to act as a gateway between the VIP terminal and the
VIP application. Generally the application is a remote DSA
application.
It manages the screen and printer devices of the VIP terminal
station.
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RFC 1921 TNVIP Protocol March 1996
In the following example figure, the "TNVIP server" is a DSA server
and manages three VIP terminal units TU1, TU2 and TU3.
Generic access
--------------
!----> LD 1S ----> DV 1S (screen) ---->!
MB 1 --> SN 1 TU 1
!----> LD 1P ----> DV 1P (printer) ---->!
Specific accesses
-----------------
!----> LD 2S ----> DV 2S (screen) ---->TU 2
MB 2 --> SN 2
!----> LD 2P ----> !
!
!----> LD 3P ----> DV 3S (printer) ---->!
MB 3 --> SN 3 TU 3
!----> LD 3S ----> DV 3P (screen) ---->!
Each Terminal Unit (TU object) is declared as containing one or two
devices (DV objects). The Terminal Manager maps this physical
representation to a logical representation where the station (SN
object) is the logical representation of a terminal unit, and the
logical device (LD) object a logical representation of the real
device.
- TU1 will be chosen by default on generic request (without mailbox
name) or by the MB1 name addressing on specific request. It can
manage the associated printer device.
- MB2 will be addressed to access the TU2 terminal unit. TU2 is
defined in a specific way because it will be presented to the host
application as a station composed of a screen (the TU2 one's) and
a printer (the TU3 one's).
- MB3 will be addressed to access TU3 terminal unit. TU3 is also
defined in a specific way because the printer device is shared by
several logical stations (SN2 and SN3) and must be well
identified.
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RFC 1921 TNVIP Protocol March 1996
Each TNVIP message is delimited by the Telnet EOR command.
Therefore, a TNVIP message has the following format:
<TNVIP Header> <parameters> <IAC EOR>
The TNVIP header is mandatory and have a fixed length of two bytes.
Some TNVIP messages need no parameter. In this case, the TNVIP
message has the following construction:
<TNVIP Header> <IAC EOR>
It is strongly recommended that Telnet commands (other than IAC IAC)
should be sent between TNVIP messages, with no TNVIP header and no
trailing IAC EOR. If a TNVIP data message containing any other IAC-
command sequence (other than IAC IAC) is received, it is
implementation dependent when the IAC-command sequence will be
processed, but it must be processed. The receiver may process it
immediately, which in effect causes it to be processed as if it had
been received before the current TNVIP message, or the processing may
be deferred until after the current TNVIP message has been processed.
It is because of this ambiguity that the presence of Telnet commands
within a TNVIP message is not recommended; neither "TNVIP client"s
nor "TNVIP server"s should send such data.
The TNVIP header contains 2 bytes. The first one indicates the
address <ADR> and the second the command <CDE>.
The <ADR> address field is mandatory and is defined on one byte.
The TNVIP protocol defines 3 addresses:
- ADR = SCREEN = 96 (0x60) for the screen commands flow,
- ADR = PRINTER = 104 (0x68) for the printer commands flow,
- ADR = SCPM = 105 (0x69) for the screen copy printing commands
flow.
A request message with an unknown or unsupported address will be
discarded by the receiver which replies with a NOT-AVAILABLE response
message.
Dujonc Informational [Page 12]
RFC 1921 TNVIP Protocol March 1996
The <CDE> command field is mandatory and defined on one byte.
The command byte <CDE> is structured as follows:
<Command-Type><Message-Type>
- The Command-Type fills the six most significant bits of the <CDE>
byte. The most significant bit is always 0.
Its value is ranged from 0 to 31 included. It defines the command
associated to the message for the flow identified by the address
field.
- The Message-Type fills the two less significant bits of the <CDE>
byte.
0 = Indication message. No response message is expected. An
indication message with an undefined command type or with an
unknown address is deleted and ignored.
1 = Request message. The sender of a request message is waiting
for a response message having the same address value. When a
request message is sent for a given address, it is not allowed to
send another request to the same address before the receiving
response. If an end point receives a request before having sent
the response of the previous request, it deletes the second
request but have to send back a PROTOCOL-VIOLATION response after
the response of the first request. A request message with a not
defined address is replied to by a NOT-AVAILABLE response message.
A request message with an unknown or unsupported command <CDE> for
this address will be deleted by the receiver and replied to by an
UNKNOWN-COMMAND response message.
2 = Response message. This message is the response to the current
request message. The receiver of this message is allowed to send
another request message on the flow defined by the ADR field.
3 = Response and request message. This message is a positive
response to the current request message sent by the receiver, but
is also a request message.
Dujonc Informational [Page 13]
RFC 1921 TNVIP Protocol March 1996
The following table gives the <CDE> commands list with their
hexadecimal values
Command Indication Request Response Resp/Req
--------------------------------------------------------
DATA 00 01
PASSW 04 05
ACK 0A
ERROR 0E
BUSY 12
ABORTED 16
PURGED 1A
NOT-AVAILABLE 1E
PROTOCOL-VIOLATION 22
UNKNOWN-COMMAND 26
PURGE 28
LOCAL-STATE 2D
ONLINE-STATE 30
STATE-REQ 35
READY 3A
STANDBY 3E
COPY-REQ 41
LOCAL-COPY 47
These messages are defined to transport in the parameter field of the
TNVIP message, the data in the terminal presentation negotiated by
the "Terminal Type" telnet command.
The parameter has the following format:
<FC1> <FC2> <STX> < screen data>
- The FC1, FC2 bytes are the functions codes of the VIP procedure
transmission [9]. Their values are comprised between 32 (0x20)
included and 127 (0x7F) included.
Dujonc Informational [Page 14]
RFC 1921 TNVIP Protocol March 1996
- The STX byte is defined by the value 2 and acts as the introducer
of the screen data.
A screen data message can be sent in a request or in an indication
message. The command values are defined as follows:
<CDE> = DATA indication = 0
<CDE> = DATA request = 1
<CDE> = PASSWORD indication = 4
<CDE> = PASSWORD request = 5
Generally, the "TNVIP server" only sends indication messages to the
screen. The request message is used mainly for the printer device.
But a DSA/TNVIP gateway server should use the screen data request
message when it processes a DSA end to end acknowledgement request
from the DSA application and synchronizes the response message
receipt with the DSA end to end acknowledgement.
The password request and the password indication message are defined,
to be used by the programs in the "TNVIP client" machine which don't
emulate terminal. In this way, they have the indication that a secret
read (password acquisition) is requested by the "TNVIP server". When
the program is a terminal emulation this information is not necessary
because the data contains the terminal presentation command to
request this secret read.
Before to switch in the local state, the "TNVIP client" sends a
LOCAL-STATE request message to the "TNVIP server". This last one
sends back an acknowledgement message and suspends the screen and
printer data flow until it receives a LINE-STATE indication message.
Note: In the local state, only the messages from the "TNVIP server"
to the screen or printer devices are deleted. The messages
from the "TNVIP client" screen device or the messages
associated to others addresses are allowed.
The following command values are defined as:
<CDE> = LOCAL-STATE request = 45 (0x2D). It is sent by the "TNVIP
client". There is no parameter field.
Dujonc Informational [Page 15]
RFC 1921 TNVIP Protocol March 1996
<CDE> = ONLINE-STATE indication = 48 (0x30). It is sent by the
"TNVIP client" to indicate the "TNVIP server" is allowed to resume
the screen data flow. There is no parameter field.
These messages are indications used to respond to the screen data
request previously received.
The command values are defined as follows:
<CDE> = ACK response indication = 10 (0x0A). The screen data
previously received has been well processed or the LOCAL STATE is
acknowledged by the "TNVIP server". There is no parameter field.
<CDE> = ERR response indication = 14 (0x0E). The screen data
previously received has not been correctly processed. There is no
parameter field.
<CDE> = BUSY response indication = 18 (0x12). The screen data
previously received has been deleted because the terminal is in the
local state. There is no parameter field.
<CDE> = ABORTED response indication = 22 (0x16). The receipt of the
screen data request has been aborted by a reset terminal command.
There is no parameter field.
<CDE> = PURGED response indication = 26 (0x1A). The processing of
the screen data request has been aborted by a purge indication
message. There is no parameter field.
<CDE> = NOT-AVAILABLE response indication = 30 (0x1E). The screen
device is not supported. Normally this command has never to be
generated because the screen device should always be present. There
is no parameter field.
<CDE> = PROTOCOL-VIOLATION response indication = 34 (0x22). The
screen request received has been deleted because an other screen
request is already in process. That means several screen request
messages have been sent without waiting for the response. It is a
consequence of the non-compliance of the protocol. There is no
parameter field.
<CDE> = UNKNOWN-COMMAND response indication = 38 (0x26). The screen
request received has been deleted because the <CDE> field value is
unknown. It is a consequence of the non-compliance of the protocol.
There is no parameter field.
Dujonc Informational [Page 16]
RFC 1921 TNVIP Protocol March 1996
The page overflow processing is not supported through the TNVIP
protocol to avoid the retransmission of the message. That leads the
"TNVIP client" side to process it locally. When a data message
induces a page overflow, the terminal emulation alerts the user
possibly requesting (in manual mode) an "enter" action before
clearing the screen and reprocessing the data received.
Note: When the "TNVIP client" is processing a page overflow , the
terminal emulation should be in the BUSY state and should
stop getting message from the line ("TNVIP server") until the
page overflow processing is complete.
This message is used to purge the current screen request message.
When the side which receive the message has not already acknowledged
the screen request, it tries to abort the processing of the request
and returns a screen purged response message. If it has already
replied, it ignores and deletes the message.
The following command value is defined as:
<CDE> = PURGE indication = 40 (0x28). There is no parameter field.
All the following messages contain the PRINTER value 104 (0x68) in
the ADR field. The support of this address is optional. If the "TNVIP
server" doesn't address this device, no message with this address
will be exchanged. If the "TNVIP client" receives a request message
with this address and does not support the printer, it replies with a
printer NOT-AVAILABLE response message.
These messages are defined to transport the printer data in the
parameter field of the TNVIP message. These messages are only sent
from the "TNVIP server" to the "TNVIP client".
The parameter has the following format:
<FC1> <FC2> <STX> <printer data>
- The FC1, FC2 bytes are the function codes of the VIP procedure
transmission. Their values are ranged from 32 (0x20) to 127
(0x7F) included.
Dujonc Informational [Page 17]
RFC 1921 TNVIP Protocol March 1996
- The STX byte is defined by the value 2 and acts as the introducer
of the printer data.
To manage correctly the printer device, the protocol only defines
request message. Whereas the "TNVIP server" is ensured than the
"TNVIP client" processes a screen data message only when the previous
one have been processed. When it receives a printer data message, the
"TNVIP client" transfers it in the printer buffer. The terminal is
busy only during this transfer. So, if the "TNVIP client" receives
another printer data it deletes them because the previous printing
(transfer between the printer buffer and the printer) is not ended.
The printer data structure depends on the terminal presentation
family (P200 or 7800). The two presentations define two modes of
printing. The first one needs the printer data are in the
presentation of the screen (7800 or P200 commands) and data are
converted by the terminal in the printer presentation (TTY, SDP,
copy. The second mode allows to give the printer data in the real
presentation of the printer. For this reason it is called
"transparent print".
In the P200 terminal presentation, transparent print data are
introduced by the sequence of the two ASCII characters ESC Z (0x1B
0x5A ). P200 formatted print are introduced by the sequence of two
ASCII characters ESC X (0x1B 0x58) or ESC Y (0x1B 0x59).
In the 7800 terminal presentation, transparent print data are
introduced by the command PTD (Print Transparent Data). 7800
formatted print are introduced by the command PHD (Print Host Data).
<CDE> = DATA request = 1 (0x01).
These messages are used to report the printing end status of the
printer data request previously received.
The following command values are defined as:
<CDE> = ACK response indication = 10 (0x0A). The printer data
previously received have been well processed.
<CDE> = ERR response indication = 14 (0x0E). The printer data
previously received have not been correctly processed (invalid
command, buffer overflow , printer off...)
<CDE> = BUSY response indication = 18 (0x12). The printer data
received have been deleted because the previous printing request is
Dujonc Informational [Page 18]
RFC 1921 TNVIP Protocol March 1996
not ended. Several printer data request messages have been sent
without waiting for the response.
<CDE> = ABORTED response indication = 22 (0x14). The printing has
been aborted by the terminal operator.
<CDE> = PURGED response indication = 26 (0x18). The printing request
has been aborted by a printer data purge indication message.
<CDE> = NOT-AVAILABLE response indication = 30 (0x1E). The printer
device is not supported.
<CDE> = PROTOCOL-VIOLATION response indication = 34 (0x22). The
printer request received has been deleted because an other printer
request is already in process. That means several printer request
messages have been sent without waiting for the response. It is a
consequence of the non-compliance of the protocol. There is no
parameter field.
<CDE> = UNKNOWN-COMMAND response indication = 38 (0x26). The
printer request received has been deleted because of an unknown
<CDE> field value. It is a consequence of the non-compliance of the
protocol. There is no parameter field.
For all the above commands, the parameter field may contain
specific terminal status if one was requested in the printer data
received (response to PDENQ 7800 terminal presentation command).
When emulating a 7800 terminal [8], the "TNVIP client" takes charge
of adding to the printer data the printer differed status request
(PDENQ 7800 command) to synchronize the printing end with the sending
of the printer acknowledgement response.
Some DSA applications are written to manage the 7800 printer status,
so they send themselves the printer status request at the beginning
of the printer data. That is the reason why when the "TNVIP client"
receives this command at the beginning of the printer data, it must
send back the 7800 status response in the parameter field of the
printer data response message.
The 7800 terminal presentation defines also immediate printer status
request and response (PENQ which allows to get an immediate response
indicating the current printer status). These commands have to be
exchanged in the TNVIP screen data flow.
Dujonc Informational [Page 19]
RFC 1921 TNVIP Protocol March 1996
This message is sent by the "TNVIP server" to know the printer state
of the "TNVIP client" without sending printer data.
The following command value is defined as:
<CDE> = STATE-REQ request = 53 (0x35). There is no parameter field.
These messages are sent by the "TNVIP client" in order to report the
printer state to the "TNVIP server".
The following command values are defined as:
<CDE> = READY response indication = 58 (0x3A). The printer state is
ready to print. There is no parameter field.
<CDE> = STANDBY response indication = 62 (0x3E). The printer device
is in standby and is temporarily unavailable. There is no parameter
field.
<CDE> = PURGED response indication = 26 (0x1A). The printer state
request has been aborted by a printer state purge indication
message. There is no parameter field.
<CDE> = NOT-AVAILABLE response indication = 30 (0x1E). The printer
device is not supported. There is no parameter field.
<CDE> = PROTOCOL-VIOLATION response indication = 34 (0x22). The
printer state request received has been deleted because an other
printer request is already in process. That means several printer
request messages have been sent without waiting for the response. It
is a consequence of the non-compliance of the protocol. There is no
parameter field.
<CDE> = UNKNOWN-COMMAND response indication = 38 (0x26). The printer
state request received has been deleted because the <CDE> field
value is unknown. It is a consequence of the non-compliance of the
protocol. There is no parameter field.
This message is used by the "TNVIP server" to purge the current
printer request message. When the "TNVIP client" receives this
message, if it has not already acknowledged the printer data, it
aborts the printing and returns a printer data purge acknowledgement
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RFC 1921 TNVIP Protocol March 1996
response message. If it has already replied, it ignores and deletes
the message.
The printer purge command value is defined as:
<CDE> = PURGE indication = 40 (0x28). There is no parameter field.
As the printer device can be used by the "TNVIP server", if the
terminal user wishes a screen copy printing, the "TNVIP" client has
to synchronize the user request with the "TNVIP server" printing .
The TNVIP protocol defines that the "TNVIP client" has to inform the
"TNVIP server" when it wants to print a screen copy and waits for its
authorization before beginning
The following command values are defined as:
<CDE> = COPY-REQ request = 65 (0x41). It is used from the "TNVIP
client" to the "TNVIP server" to request a screen copy printing.
<CDE> = LOCAL-COPY response and request = 71 (0x47). It is sent by
the "TNVIP server" to acknowledge the COPY-REQ message indicating
the screen copy can be done locally. It is also a request message
because it is equivalent to a screen copy data request message and
the "TNVIP server" is waiting for a screen copy response message
from the "TNVIP client" but on the SCPM flow. There is no parameter
field.
They are defined in order to transport in the parameter of the
message the screen copy data in the terminal presentation. It is used
by the "TNVIP client" when it wants to send the screen copy data
directly to the DSA application (a VIP terminal using a VIP
transmission procedure indicates this special request by the STA byte
=PRT=0x1A).
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RFC 1921 TNVIP Protocol March 1996
The parameter field has the following format:
<FC1> <FC2> <STX> <screen-copy-data>
- The FC1, FC2 bytes are the functions codes of the VIP procedure
transmission. Their values are ranged from 32 (0x20) to 127
(0x7F) included.
- The STX byte is defined by the value 2 and acts as the introducer
of the screen data.
Screen copy data message can be sent in a request or indication
message.
The command values are defined as follows:
<CDE> = DATA indication = 0
<CDE> = DATA request = 1
These messages are sent by the "TNVIP client" (local copy) to report
the end of printing status of the screen copy.
The ACK response is also used by the "TNVIP server" to acknowledge a
screen copy data request sent to the host application.
The ERR message is also used by the server to refuse a COPY-REQ
message.
The following command values are defined as:
<CDE> = ACK response indication = 10 (0x0A). The "TNVIP client"
reports the screen copy has been well printed or the "TNVIP server"
acknowledges the screen copy data request. There is no parameter
field.
<CDE> = ERR response indication = 14 (0x0E). The screen copy has not
been correctly printed (invalid command, buffer overflow ...) or has
been refused by the "TNVIP server". It can optionally contain a
reason code value defined on one byte.
- 1 : The printer is busy, retry later.
<CDE> = BUSY response indication = 18 (0x12). The screen copy has
not been correctly printed because the printer device is already
printing. There is no parameter field.
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<CDE> = ABORTED response indication =22 (0x16). The screen copy has
been aborted by the terminal operator. There is no parameter field.
<CDE> = PURGED response indication = 26 (0x1A). The screen copy
request message has been aborted by a purge indication message.
There is no parameter field.
<CDE> = NOT-AVAILABLE response indication = 30 (0x1E). The screen
copy has not been correctly printed because the printer device is
not supported. There is no parameter field.
<CDE> = PROTOCOL-VIOLATION response indication = 34 (0x22). The
screen copy request received has been deleted because an other
screen copy request is already in process. That means several screen
copy request messages have been sent without waiting for the
response. It is a consequence of the non-compliance of the protocol.
There is no parameter field.
<CDE> = UNKNOWN-COMMAND response indication = 38 (0x26). The screen
copy request received has been deleted because the <CDE> field value
is unknown. It is a consequence of the non-compliance of the
protocol. There is no parameter field.
This message is used to purge the current screen copy request
message. When the "TNVIP server" or the "TNVIP client" receives this
message, if it has not already acknowledged the request message, it
returns a screen copy purge acknowledgement message. If it has
already replied, it ignores and deletes the message.
The following command value is defined as:
<CDE> = PURGE indication = 40 (0x28).There is no parameter field.
The TM attention is the signal used to activate the local dialog of
the DSA Terminal Manager.
The Telnet Abort Output (AO) command [1] is the mechanism used to
implement the TM attention key support in TNVIP.
IAC AO (0xFF 0xF5)
In order to implement the TM attention key support, "TNVIP clients"
should provide a key (or combination of keys) that is identified as
mapping to the TM attention key. When the user presses this key(s),
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RFC 1921 TNVIP Protocol March 1996
the "TNVIP client" should transmit a Telnet AO command to the "TNVIP
server".
Upon receipt of the AO command, a "TNVIP server" that implements the
DSA Terminal Manager should enter in what will be loosely termed "TM
Local Dialog", suspending the eventual DSA host connection, else it
should simply ignore it.
Generally, there is no break key on the real VIP terminal. The break
signal is transmitted to the host application through a TM local
dialog command ($*$BRK for example)
On "TNVIP client" emulating VIP terminal, it is often possible to map
the break signal on a special key combination or by other way (using
mouse ...).
The Telnet Break (BRK) command [1] is used to map the Break signal of
the TNVIP.
IAC BRK (0xFF 0xF3)
The Telnet Interrupt Process (IP) command [1] can be used to map the
logout command of the TM Local Dialog ($*$LO for example) if it is
implemented on the "TNVIP server".
IAC IP (0xFF 0xF4)
Data request (allowed in the two ways)
SCREEN DATA-REQ <FC1> <FC2> STX [<screen-data>] IAC EOR
60 01 <FC1> <FC2> 02 [<screen-data>] FF EF
- Allowed responses to the screen Data request.
SCREEN ACK IAC EOR
60 0A FF EF
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RFC 1921 TNVIP Protocol March 1996
SCREEN ERROR IAC EOR
60 0E FF EF
SCREEN BUSY IAC EOR
60 12 FF EF
SCREEN ABORTED IAC EOR
60 16 FF EF
SCREEN PURGED IAC EOR
60 1A FF EF
Password request (only from the "TNVIP server" to the "TNVIP client")
SCREEN PASSW-REQ <FC1> <FC2> STX [<screen-data>] IAC EOR
60 05 <FC1> <FC2> 02 [<screen-data>] FF EF
- Allowed responses to the password request.
SCREEN ACK IAC EOR
60 0A FF EF
SCREEN ERROR IAC EOR
60 0E FF EF
SCREEN BUSY IAC EOR
60 12 FF EF
SCREEN ABORTED IAC EOR
60 16 FF EF
SCREEN PURGED IAC EOR
60 1A FF EF
Local state request (only from the "TNVIP client" to the "TNVIP
server").
SCREEN LOCAL-ST IAC EOR
60 2D FF EF
- Allowed responses to the Local state request.
SCREEN ACK IAC EOR
60 0A FF EF
SCREEN PURGED IAC EOR
60 1A FF EF
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Responses to request violating the TNVIP protocol (allowed in the two
ways)
SCREEN NOT-AVAIL IAC EOR
60 0E FF EF
SCREEN PROT-VIOL IAC EOR
60 22 FF EF
SCREEN UNKN-CDE IAC EOR
60 26 FF EF
Indications (allowed in the two ways)
SCREEN DATA-IND <FC1> <FC2> STX [<screen-data>] IAC EOR
60 00 <FC1> <FC2> 02 [<screen-data>] FF EF
SCREEN PURGE IAC EOR
60 28 FF EF
Password indication (only from the "TNVIP server" to the "TNVIP
client").
SCREEN PASSW-IND <FC1> <FC2> STX [<screen-data>] IAC EOR
60 04 <FC1> <FC2> 02 [<screen-data>] FF EF
On line state indication (only from the "TNVIP client" to the "TNVIP
server").
SCREEN ONLINE-ST IAC EOR
60 30 FF EF
Data request (only from the "TNVIP server" to the "TNVIP client")
PRINTER DATA-REQ <FC1> <FC2> STX [<printer-data>] IAC EOR
68 01 <FC1> <FC2> 02 [<printer-data>] FF EF
- Allowed responses to the printer data request.
PRINTER ACK [<status>] IAC EOR
68 0A [<status>] FF EF
PRINTER ERROR [<status>] IAC EOR
68 0E [<status>] FF EF
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RFC 1921 TNVIP Protocol March 1996
PRINTER BUSY [<status>] IAC EOR
68 12 [<status>] FF EF
PRINTER ABORTED [<status>] IAC EOR
68 16 [<status>] FF EF
PRINTER PURGED [<status>] IAC EOR
68 1A [<status>] FF EF
PRINTER NOT-AVAIL [<status>] IAC EOR
68 1E [<status>] FF EF
State request (only from the "TNVIP server" to the "TNVIP client")
PRINTER STATE-REQ IAC EOR
68 35 FF EF
- Allowed responses to the state request.
PRINTER READY IAC EOR
68 3A FF EF
PRINTER STANDBY IAC EOR
68 3E FF EF
PRINTER PURGED IAC EOR
68 1A FF EF
PRINTER NOT-AVAIL IAC EOR
68 1E FF EF
Responses to request violating the TNVIP protocol (allowed in the two
ways)
PRINTER PROT-VIOL IAC EOR
68 22 FF EF
PRINTER UNKN-CDE IAC EOR
68 26 FF EF
Indication (only from the "TNVIP server" to the "TNVIP client")
PRINTER PURGE IAC EOR
68 28 FF EF
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RFC 1921 TNVIP Protocol March 1996
Copy request (only from the "TNVIP client" to the "TNVIP server")
SCPM COPY-REQ IAC EOR
69 41 FF EF
- Allowed responses to the copy request (from the "TNVIP server" to
the "TNVIP client")
SCPM ERROR <reason> IAC EOR
69 0E <reason> FF EF
SCPM PURGED IAC EOR
69 1A FF EF
SCPM NOT-AVAIL IAC EOR
69 1E FF EF
SCPM LOCAL-COPY-RQ IAC EOR
69 47 FF EF
Local copy request (only from the "TNVIP server" to the "TNVIP
client" )
SCPM LOCAL-COPY-RQ IAC EOR
69 47 FF EF
- Allowed responses to the local copy request (from the "TNVIP
client" to the "TNVIP server").
SCPM ACK IAC EOR
69 0A FF EF
SCPM ERROR IAC EOR
69 0E FF EF
SCPM BUSY IAC EOR
69 12 FF EF
SCPM ABORTED IAC EOR
69 16 FF EF
SCPM PURGED IAC EOR
69 1A FF EF
SCPM NOT-AVAIL IAC EOR
69 1E FF EF
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RFC 1921 TNVIP Protocol March 1996
Data request. (only from the "TNVIP client" to the "TNVIP server")
SCPM DATA-REQ <FC1> <FC2> STX [<screen-data>] IAC EOR
69 01 <FC1> <FC2> 02 [<screen-data>] FF EF
- Allowed responses to the data request
SCPM ACK IAC EOR
69 0A FF EF
SCPM PURGED IAC EOR
69 1A FF EF
SCPM NOT-AVAIL IAC EOR
69 1E FF EF
Responses to request violating the TNVIP protocol (allowed in the two
ways)
SCPM PROT-VIOL IAC EOR
69 22 FF EF
SCPM UNKN-CDE IAC EOR
69 26 FF EF
Indications (allowed in the two ways)
SCPM DATA-IND <FC1> <FC2> STX [<screen-data>] IAC EOR
69 00 <FC1> <FC2> 02 [<screen-data>] FF EF
SCPM PURGE IAC EOR
69 28 FF EF
Security issues are not addressed in this document. It is
anticipated that once authentication mechanisms have become well
established, use of them can be made by TNVIP. One of the important
uses of authentication would be to answer the question of whether or
not a given user should be allowed to "use" a specific terminal.
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