can't read "ns_": no such variable

Question

I am new in ns2 simulation, if this question is easy I am sorry for that.This is my tcl code and I created my scenario file with this code:

./setdest -n 250 -p 0.0 -M 10.0 -t 10 -x 1500 -y 1500 > S250

and also

ns cbrgen.tcl -type tcp -nn 250  -seed 1.0 -mc 100 > T250

but when i tried run simulation i shown this error.

can't read "ns_": no such variable
    while executing
"global $ns_"
    (file "wireless.tcl" line 24)

Can you help me about this topic? It would be much appreciated.

  # ======================================================================
# Define options
# ======================================================================
set val(chan)           Channel/WirelessChannel    ;# channel type
set val(prop)           Propagation/TwoRayGround   ;# radio-propagation model
set val(netif)          Phy/WirelessPhy            ;# network interface type
set val(mac)            Mac/802_11                 ;# MAC type
set val(ifq)            Queue/DropTail/PriQueue    ;# interface queue type
set val(ll)             LL                         ;# link layer type
set val(ant)            Antenna/OmniAntenna        ;# antenna model
set val(ifqlen)         50                         ;# max packet in ifq
set val(nn)             250                        ;# number of mobilenodes
set val(rp)             AODV                       ;# routing protocol
set val(cp)             T250        
set val(sc)             S250                

# ==================================================== =================
# Main Program
# ======================================================================

set ns    [new Simulator]
set tracefd     [open out.tr w]
set winfile  [open winFile w]
global $ns_

$ns trace-all $tracefd
set namtrace    [open out.nam w]
$ns namtrace-all-wireless $namtrace 1500 1500

set topo    [new Topography]
$topo load_flatgrid 1500 1500

create-god $val(nn)

$ns node-config -adhocRouting $val(rp) \
                 -llType $val(ll) \
                 -macType $val(mac) \
                 -ifqType $val(ifq) \
                 -ifqLen $val(ifqlen) \
                 -antType $val(ant) \
                 -propType $val(prop) \
                 -phyType $val(netif) \
                 -channelType $val(chan) \
         -topoInstance $topo \
         -agentTrace ON \
                 -routerTrace ON \
                 -macTrace OFF \
          -mvementTrace ON \

for {set i 0} {$i < $val(nn) } {incr i} {
    set node_($i) [$ns_ node]
}
puts "Loading scenario file..."
source $val(sc)

puts "Loading connection pattern..."
source $val(cp)

# Tell nodes when the simulation ends

for {set i 0} {$i < $val(nn) } {incr i} {
    $ns_ at 10.0 "$node_($i) reset";
}

$ns_ at 10.0 "stop"
$ns_ at 10.01 "puts \"NS EXITING...\" ; $ns_ halt"
proc stop {} {

    global ns_ tracefd
    $ns_ flush-trace
    close $tracefd
        exec nam out.nam &
        exit 0
}

puts "Starting Simulation..."
$ns_ run

Answer 1

Try

global ns_

instead of

global $ns_

ns_ is the name of the varible. $ns_ is the variable's value. You declare it by its name.

Answer 2

In fact, the Answer is simple, you didn't declare the variable "ns_" in the global memory space.

I explained it in detail in the following link

http://www.projectguideline.com/topic/cant-read-ns_-no-such-variable-what-causes-this-ns-2-error/