Specifications

Interfaces
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for a response from the target by using the Read-identity-poll
function. If the target has not reserved the console or a timer
expires! the process is repeated.
The target system's console server must be able to process the console
reservation from the host system and will open its console to the host
system if all the necessary conditions are met. Once the console is
reserved, the user process in the target systemI i.e.! that system's
console processorl must be periodically polling the Console Server for
console commands using the Request-poll function.
When both systems are ready to
communicatel the command system has the
responsibility both to transmit commands and poll for responses from
the target system. The target system has to respond to console
command and poll messages and maintain the console reservation timer.
When the command system has data to send! it calls the Send-console-
command functionI then waits for the response by periodically calling
the Console-response-poll function. If a failure is observed, the
command system makes any necessary corrections and reissues the Senci-
console-command. This process is repeated until all pending command
data has been sent and acknowledged. If data was returned with the
final acknowledgmentl
it is processed and another Send-console-command
call is made to "flush" the remote console response buffer. Even when
there is no data to send or being returned! the command system still
must periodically call the
Send-console-command function to keep the
reservation alive and to receive possible unsolicited "response" data
from the remote console. If the command system does not receive a
response to a Send-console-command within a specified "no response
time!'' then it calls the Console-abort function and issues a Request-
identity to try to ascertain the state of the target system and the
reasor, for its failure to respond.
At the other end, the target system's user process must periodically
call the Request-poll function. When the user process receives a
console command it must process it and acknowledge it by calling
the
Send-console-response function.
At either end! data overrun is blocked by the Console Responder or
Server returning an error status code to the user
if the previous
message has not been acknowledged. Unblocking of a data stream that
may have experienced some kind of prolonged discontinuity is achieved
by the command system detecting the error conditionI releasing and
then re-reserving the target console. This will force the target
system to reinitialize its Console Server andI hopefullyI unblock the
data stream.