Virtual Terminal (VT) emulation troubleshooting checklist

1. Cannot access online help from VT session properties
2. Emulating the VT keyboard in Host On-Demand by remapping the NumLock key
3. VT 420 features that are not implemented
4. VT 420 keyboard limitations
5. VT 420 character set limitations
6. VT-UTF8 character set limitations

1. Cannot access online help from VT session properties

   While using the Terminal Properties > History window in VT session properties, the Help button may launch a blank online help file in a separate browser. To display the contents of the help file, close the session properties window.

2. Emulating the VT keyboard in Host On-Demand by remapping the NumLock key

   The NumLock key toggles NumLock function states when remapped. The circumvention for this is to map both the NumLock on and NumLock off keys to the same value, and then map the scrolling key values to an ALT+key sequence. You can use the Host On-Demand Administration client or the Deployment Wizard to remap the keys.

   For example, using these predefined Host Functions,

   • F1 NumLock
   • F2 Keypad /
   • F3 Keypad *
   • F4 Keypad -
   1. Map the keypad with NumLock on:
      • Keypad 0 Numpad 0
      • Keypad 1 Numpad 1
      • Keypad 2 Numpad 2
      • Keypad 3 Numpad 3
      • Keypad 4 Numpad 4
      • Keypad 5 Numpad 5
      • Keypad 6 Numpad 6
      • Keypad 7 Numpad 7
      • Keypad 8 Numpad 8
      • Keypad 9 Numpad 9
      • Keypad . Numpad .
      • Keypad Enter Numpad +
   2. Map the keypad with NumLock off:

      When you remap the following keys, a pop-up box appears. Click OK, and an additional entry appears in the table in the keyboard remap screen for the key.

      • Keypad 0 (Keypad) Ins
      • Keypad 1 (Keypad) End
      • Keypad 2 (Keypad) Down
      • Keypad 3 (Keypad) PageDown
      • Keypad 4 (Keypad) Left
      • Keypad 5 (Keypad) Clear
      • Keypad 6 (Keypad) Right
      • Keypad 7 (Keypad) Home
      • Keypad 8 (Keypad) Up
      • Keypad 9 (Keypad) PageUp
      • Keypad . (Keypad) Del
   3. Remap Editing Functions to Alt Sequences (make sure NumLock is off)
      • Insert Alt + (Keypad) Ins
      • Find Alt + (Keypad) End
      • Cursor Down Alt + (Keypad) Down Arrow
      • NextScreen Alt + (Keypad) PageDown
      • Cursor Left Alt + (Keypad) Left Arrow
      • Clear Alt + (Keypad) Clear
      • Cursor Right Alt + (Keypad) Right Arrow
      • Select Alt + (Keypad) Home
      • Cursor Up Alt + (Keypad) Up Arrow
      • PrevScreen Alt + (Keypad) PageUp
      • Remove Alt + (Keypad) Del
3. VT 420 features that are not implemented

   The following VT 420 features are not implemented:

   • Display Controls Mode
   • Keyboard Layout and Control
   • User-Preferred Supplemental Set
   • PC Term Mode
   • Terminal State Reports

   Note:  There are 2 commands for the Terminal State Reports feature, including Request Terminal State Report and Restore Terminal State.  Host On-Demand Version 9.0 supports only the Request Terminal State Report with a fixed value.  

4. VT 420 keyboard limitations

   Some local function keys cannot be enabled or disabled in Host On-Demand VT sessions, and menu keys that are mapped to menu commands are not available as local function keys. For example:

   • Ctrl+C is not available for mapping copy to clipboard
   • Ctrl+A is not available for select (Mark) item

   The following VT modifier keys are not visible to Host On-Demand VT sessions:

   • Left Shift
   • Right Shift
   • Lock
   • Left Alt Function
   • Right Alt Function
   • Left Compose Character
   • Right Compose Character

   The DECEKBD report is not supported due to technical limitations regarding the determination of the state of the keys on the keyboard.

   Due to limitations in Java keyboard handling, Host On-Demand does not map by default the numeric keypad keys so that they can differentiate between numeric mode and application mode.

5. VT 420 character set limitations

   All characters in the terminal screen must be stored as Unicode values. The following character sets contain characters that cannot be matched to a Unicode value:

   Character Set	Position
   Dec Technical Character set	31
   PC Multilingual/International - Left Side	08, 17
   PC Multilingual - Right Side	9B
   PC Spanish	A9, AA
   PC Danish/Norwegian	9B

   In some session configurations, Host On-Demand does not offer you the option of selecting a raster font for a VT Display session. This restriction occurs:

   • When some host code pages are selected, such as Chinese (Simplified), Chinese (Traditional), Japanese, and Korean. (To select a host code page, click an entry in the Host Code Page list in the Connection window of the session configuration.)
   • When Fixed Font is set to Yes in the Font window of the session configuration.

   The raster fonts are IBM3270, ARB3270 (Arabic), HEB3270 (Hebrew), and THA3270 (Thai). Non-raster fonts include Monospaced, Courier New, Letter Gothic, and others.

   When a VT Display session is configured with a non-raster font, then Host On-Demand's VT emulation is dependent on the Java Virtual Machine's available set of fonts for rendering the VT terminal screen. Each operating system and browser combination is missing some of the characters contained in a few of the new character sets. The number of non-renderable characters and their positions varies by operating system and browser, so they are not listed here.

   VT-UTF8 character set limitations

   When running in UTF-8 mode please be aware of the following limitations:

   1. When invalid UTF8 formatted data is received, the character is discarded.
   2. Ensure the host is configured for UTF-8, otherwise, unexpected results can occur.  If the default for the host machine is not UTF-8, the logon screen might display incorrectly.
   3. Since Monospaced font is the default, the vertical box draw characters will have spaces between them.