PortStore5 Manual
HW group
www.HW-group.com
33
NVT control
The following is a short overview of controlling the PortStore via the M2M NVT protocol. It is an
extract from the detailed description of NVT that is available at our website:
http://www.hw-group.com/support/nvt/index_en.html
What is NVT and RFC2217
NVT is a method of embedding control commands into a binary data stream. NVT (Network Virtual
Terminal) is also used by the Telnet protocol to transfer commands. In this way, Telnet transfers
control sequences such as CTRL-Pause, cursor positioning on the screen, changing terminal type,
and so on.
For remote control of serial ports, Cisco has defined RFC2217 that defines commands for changing
the serial port speed, querying the states of digital I/O signals, etc. Our devices implement most of
these commands. For a list, see the online description of NVT at the above-mentioned website.
We extended the standard RFC2217 commands to
include several GPIO (General Pin Input/Output)
functions listed below. These functions can control the
digital input and output pins of PortStore5. Our extension
is not standardized; however, when we implemented this
extension in 2001, no such standard was known to us.
How does it work
The commands are control sequences in the TCP/IP
data stream; the “FF” character starts the control
sequence with a defined format. If the “FF” (255 decimal)
character appears in the normal data, it must be doubled
at the transmitting side. The receiving side automatically
converts a double “FF” to a single “FF”. When both sides
support NVT, the „FF” character always prefixes a control
sequence.
Supported NVT commands
COM-PORT-OPTION - 44 (2C)
Dec
HEX
Function
0
00
CAS_SIGNATURE
1
01
CAS_SET_BAUDRATE
2
02
CAS_SET_DATASIZE
3
03
CAS_SET_PARITY
4
04
CAS_SET_STOPSIZE
5
05
CAS_SET_CONTROL
6
06
CAS_NOTIFY_LINESTATE
7
07
CAS_NOTIFY_MODEMSTATE
8
08
CAS_FLOWCONTROL_SUSPEND
9
09
CAS_FLOWCONTROL_RESUME
10
0A
CAS_SET_LINESTATE_MASK
11
0B
CAS_SET_MODEMSTATE_MASK
12
0C
CAS_PURGE_DATA
50
32
CAS_OPT_GPIO
51
33
CAS_SET_GPIO
52
34
CAS_SET_GPIOM
:
:
+100
+64
ASC_
150
96
ASC_OPT_GPIO
151
97
ASC_SET_GPIO
152
98
Not implemented, one way "answer" only
Values up to 100 Dec =
Client >> Server
Values over 100 Dec =
Server >> Client
CAS_
request for the device to perform a command
ASC_
device response, command per confirmation
Commands start with <IAC><SB> (
FF FA
) and end with
<IAC><SE> (
FF F0
).
