Visara LINCS Features - Manual (Page 68)

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LINCS Features
707021-001
TN3270E clients per RFC 1647. The TN3270E server software feature, for LINCS with the
appropriate software expansion FAD, consists of an extension of the current TELNET feature
to allow a TELNET client attached via Ethernet or Token Ring to receive 3270 data. LINCS
acts as a TN3270E server and the terminal is the TN3270 client.
When an incoming TELNET connection is established certain TELNET options can be
negotiated to cause the connection to transition to a TN3270 type 3270 session. Subsequent
data from LINCS (TN3270 server) to the terminal (TN3270 client) is 3270 data to be processed
by a 3270 emulator running on the client. This allows the client to connect to a 3270 host
computer as a DFT type terminal without requiring an ASCII emulation/translation on the
server. The TN3270 client must be a TELNET client attached to the LINCS TELNET server
via Ethernet/Token Ring or be routed across a Frame Relay connection.
Client emulation must be consistent with the 3270 LU type configured on the host. The server
allows you to associate a specific LU with the client, but you must make sure that the client
emulator supports all functionality associated with that LU. The server passes all RU’s to the
client unmodified, including Write Structured Field (WSF) commands (including queries)
and orders containing a 12/14/16 bit address field. The only exception is that a non-extended
type client will not receive Write Structured Field commands. If the WSF is a query, the server
replies with a null query response on behalf of any non-extended type client. The following
client terminal types are supported:
IBM-3179-2 IBM-3180-2
IBM-3278-2 IBM-3278-3
IBM-3278-4 IBM-3278-5
IBM-3278-2-E IBM-3278-3-E
IBM-3278-4-E IBM-3278-5-E
IBM-3279-2 IBM-3279-3
IBM-3279-2-E IBM-3279-3-E
IBM-3279-4-E IBM-3279-5-E
LINCS assumes that the TN3270 client is capable of receiving an NVT ASCII data stream, the
default mode for an incoming TELNET connection. The server can be configured to send
NVT data to display a user prompt panel when the client connects.
When a TELNET client connects to the server, TELNET communication parameters are
negotiated to establish the client-server interface. The negotiated session parameters determine
whether or not this TELNET connection is a TN3270 type connection. Specifically, the End -
Of-Record and Transmit Binary TELNET options must be supported by the client and server,
and the client must negotiate IBM 32XX type terminal support using the Terminal Type
TELNET option. The server usually initiates negotiation of these options at connect time,
although either side may negotiate any option at any time. Note that the obsolete TELNET
Regime option will be refused by the server.
TN3270 and (Async) TELNET connections must use different TCP Ports on LINCS. If TN3270/
TN3270E client connections are configured and a client connects on a TCP port configured
for TN3270/TN3270E client connections, the server will attempt to negotiate the client as a
TN3270E client first (if configured) then as a TN3270 client if the client refuses TN3270E. To
connect the client as a TN3270 device, the TELNET options mentioned above will be negotiated.