Table17. 3270 Device Capabilities (continued)
Device Type Device Capabilities
3278 This display station supports extended attributes, such as blinking, reverse
image, and underlining if requested by the OS/400 DDS (data description
specifications) keywords.
Notes:
1. Extended attributes are not supported by some client implementations
of TELNET 3270 full-screen mode (TN3270).
2. DBCS terminals that negotiate a 3278-2-E terminal type are
supported.
3279 This display station supports color attributes and the extended data
stream attributes sent for a 3278 device. The color attributes are
determined (in the same manner as a 5292 Full Color Display) by
interpreting the DDS attributes as blinking, high intensity,or the DDS color
keywords.
VTxxx Full-Screen Mode
VTxxx server support allows Telnetclient users to log on and run AS/400 5250
full-screen applications even though VTxxx full-screen support is negotiated. The
Telnetclient application must be able to negotiate VTxxx terminal support. When
VTxxx full-screen mode is negotiated, the AS/400 Telnetserver is responsible for
mapping 5250 functions to VTxxx keys and vice versa.
Although the AS/400 Telnetserver supports VTxxx clients, this is not the preferred
mode to use because the AS/400 system is a block mode system, and the VTxxx
terminal is a character mode device. Most Telnetimplementations support a
TN3270 or TN5250 client that should be used when connecting to an AS/400Telnet
server.
In general, when a key on a VTxxx terminal is pressed, the hexadecimal code
associated with that key is immediately transmitted to the Telnetserver. The Telnet
server must process that keystroke and then echo that character back to the VTxxx
terminal to be displayed. This results in a large amount of overhead associated with
each keystroke. In contrast, the 5250 and 3270 block mode devices buffer all
keystrokes at the client system until an Attention Identifier (AID) key is pressed.
When an AID key is pressed, the client sends the buffered input to the server for
processing. The block mode devices result in less overhead per keystroke and
generally provide better performance than a character-mode device, such as the
VTxxx terminal.
VTxxx delivers the data between the two systems as ASCII.
Setting up for VTxxx Full-Screen Mode
Youcan use the CFGTCPTELN command to set up your VTxxx full-screen mode
session.
196 OS/400 TCP/IPConfiguration and Reference V4R4