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Hi,

  In the Marc Greis's ns Tutorial, the receivers are Agent/LossMonitor, not
Agent/Null. You can read the source file 'loss-monitor.cc' in '../ns'
directory about the implementation of Agent/LossMonitor. The variable of
'byte_' is a class member of it.

          ZXG


-----Original Message-----
������: Allan W. Yarbrough <[email protected]>
�ռ���: [email protected]; <[email protected];>;
[email protected] <[email protected]>
����: [email protected] <[email protected]>
����: 1998��12��9�� 12:10
����: Problem saving output data with ns


>All:
>
>According to the Marc Greis's ns Tutorial, the following code fragment:
>
>set null0 [new Agent/Null]
>$ns attach-agent $n3 $null0
>...
>proc record {} {
> #Redeclare the sink and file handle variables
> global null0 f0
> #get an instance of the simulator
> set ns [Simulator instance]
> #set the time after which the procedure should be called again
> set time 0.5
> #How many bytes have been received by the traffic sinks?
> set bw0 [$null0 set bytes_]
> #Get the current time
> set now [$ns now]
> #calculate the bandwidth (in MBit/s) and write it to the files
> puts $f0 "$now [expr $bw0/$time*8/1000000]"
> #Reset the bytes_values on the traffic sinks
> $null0 set bytes_ 0
> #Re-schedule the procedure
> $ns at [expr $now+$time] "record"
>}
>
>should find the number of bytes sent to the null agent $null0.  However, on
>execution, I receive the following error:
>
>ns: record: can't read "bytes_": no such variable
>    while executing
>"subst $[subst $var]"
>    (procedure "_o78" line 5)
>    (SplitObject set line 5)
>    invoked from within
>"$null0 set bytes_"
>    (procedure "record" line 9)
>    invoked from within
>"record"
>
>So basically, bytes_ is not recognized as a member of class agent.  Is
there
>another way of getting the size of agent?  I tried using size_ instead of
>bytes_, but received exactly the same error.  Is something else wrong with
my
>syntax?
>
>Cordially,
>
>Allan