User`s manual

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and modification of protected resources. The “M” command will typically work in conjunction with
the “K” command, which allows a password to be sent to the router. Some commands, such as
those that allow modification of router configuration settings, might require entry of an
administrator password before allowing the router configuration to be modified. The “K” command
is used to send the password, but the router must be able to record that password in association
with a particular remote user. The router would save the password as the one established by the
remote address specified in the “M” command. The examples below show how this would work.
If the “M” command is not present in a control string received on a serial port, the address
assigned to the serial port itself is used as the address for all commands in that command string.
The “M” command works on an honor system. There is nothing to keep a remote device from
forging a false address. This conforms with the philosophy of providing protection mechanisms
that are not designed to be totally hack-proof, but rather, are designed under the assumption that
controlling devices will honor the system. A dedicated hacker can always hack into the system if
he chooses. Note, however, that the server in a client/server relationship can provide a great deal
of added security for the system, forcing the correct “M” command to be sent each time, and
filtering out bogus “M” commands received from clients.
When the router receives an “M” command in a command string, it echoes the same “M”
command in its response. This allows the server connected to the serial port to parse the
received response string and determine to which client it should route the response.
Normally the server will assign remote addresses to its clients. However, it should always provide
a way to send these addresses to the client, because the client needs to know its address in
order to know how to interpret some responses. By simply passing each “M” response command
received from the router back to the client, the server can let the client know what its address is.
For example, the command:
** M139 K9664 !!
establishes password 9664 as the password for remote address 139. The response to this
command string would be:
** M139 OK !!
If remote address 13 later sends the command:
** M139 Y8,27 !!
to request that output 8 be connected to input 27, the router would check to see if output 8 has
been locked. If so, the router compares the password of remote address 139 (which has
previously been set to 96643) to the password that was used to lock output 8. If they match, the
connection request succeeds, but if they don’t match, output 8 is left unchanged.
“U”: Update Request on/off
The command “U” turns on or off the automatic sending of output change reports. The command
letter must be followed by either a number 0, 1, or 2 to specify the new automatic change report
state, as follows:
0: Automatic output change reporting is turned off.
1: Automatic output change reporting is turned on. Crosspoint change commands do not
immediately report changed status, but instead, the report comes up to a few seconds after the
crosspoint change command is received.
2: Automatic output change reporting is turned on, and crosspoint change commands
immediately report changed status as part of the response to the command.
Output change reports are automatic messages sent to the host whenever an output is crosspoint
status (i.e. connected source) is changed.
For example, the command:
**U1!!
Turns on automatic output change reporting. When a crosspoint is changed, the following
message might be received:
** X5,17,3 !!<CR>
indicating that output 5 is now connected to input 17 on level 3. Alternatively, if the router has only
a single level or if all levels of the output are connected the same, it might send: