A TCL tutorial

ns2.tcl

# variable and printing

set x 10
set y 25
set z [expr $x*$y]
puts $x
puts "x + y = [expr $x+$y]"

# conditional
if { $x > 9 } {
    puts "Yes"
} else {
    puts "No"
}

# while loop

while { $x <= 100 } {
puts $x
set x [expr $x + 30]
}

# for loop

for {set a 0} {$a < 5} {incr a} {
    puts $a
}

# array 

set arr(0) 5
set arr(1) 10
puts "$arr(0) $arr(1)"

# associative array

set strarr("name") "sriram"
puts $strarr("name")

# procedures that is functions

proc min {arg1 arg2} {
    if { $arg1 > $arg2 } {
        return $arg2
    }
    return $arg1
}
puts "[min 10 20]"

# global modifier ( used inside if or proc)
global x 20

# Files
# File modes: r w a r+ w+

set f [open "a.txt" w]
puts $f "Wassup"
close $

set f [open "a.txt" r]
gets $f readed
puts $readed
close $f

# Simulation Script

# Create a new simulator object
set ns [new Simulator]

# Specify a file to store all simulation results
set tr [open "out.tr" w]
$ns trace-all $tr

# Specify a file to store all animator results
set nam [open "out.nam" w]
$ns namtrace-all $nam

# Create nodes
set $n1 [new node]
set $n2 [new node]

# Create a link
# $ns duplex-link $node1 $node2 Speed Delay QueueType (usually droptail)
$ns duplex-link $n1 $n2 2Mb 4ms DropTail

# Set queue size
$ns duplex-link-op $n1 $n2 queueSize 10

# Now you need to create agents and attach to the nodes 
set tcp1 [new Agent/TCP]
set tcpsink [new Agent/TCPSink]

$ns attach-agent $n1 $tcp1
$ns attach-agent $n2 $tcpsink

$ns connect $n1 $n2

# We have to attach a application to agents to send data

set ftp [new Application/FTP]
$ftp attach-agent tcp1

# To start simulation
$ns at 1.0 "$ftp start"
$ns at 2.0 "$ftp stop"
$ns at 2.1 "Finishing simulation"
proc finish() {
    global ns tr nam
    $ns flush-all
    close $tr
    close $nam
    exec nam out.nam &
    exit
}

$ns run