Here is the second.cc:

#include $"$ns$3/$applications$-$module.h$"$

#include $"$ns$3/$core$-$module.h$"$

#include $"$ns$3/$csma$-$module.h$"$

#include $"$ns$3/$internet$-$module.h$"$

#include $"$ns$3/$ipv$4-$global$-$routing$-$helper.h$"$

#include $"$ns$3/$network$-$module.h$"$

#include $"$ns$3/$point$-$to$-$point$-$module.h$"$

$//$ Default Network Topology

$//$

$//10\mathrm{.}1\mathrm{.}1\mathrm{.}0$

$//$ n$0--------------$ n$1$ n$2$ n$3$ n$4$

$//$ point$-$to$-$point $||||$

$//================$

$//$ LAN $10\mathrm{.}1\mathrm{.}2\mathrm{.}0$

using namespace ns$3$;

NS$\_$LOG$\_$COMPONENT$\_$DEFINE$("$SecondScriptExample$")$;

int

main$($int argc, char$*$ argv$[])$

$\{$

bool verbose $=$ true;

uint$32\_$t nCsma $=3$;

CommandLine cmd$(\_\_$FILE$\_\_)$;

cmd$.$AddValue$("$nCsma$",$ "Number of $\backslash "$extra$\backslash "$ CSMA nodes$/$devices$",$ nCsma$)$;

cmd$.$AddValue$("$verbose$",$ "Tell echo applications to log if true", verbose$)$;

cmd$.$Parse$($argc$,$ argv$)$;

if $($verbose$)$

$\{$

LogComponentEnable$("$UdpEchoClientApplication$",$ LOG$\_$LEVEL$\_$INFO$)$;

LogComponentEnable$("$UdpEchoServerApplication$",$ LOG$\_$LEVEL$\_$INFO$)$;

$\}$

nCsma $=$ nCsma $==0?1$ : nCsma;

NodeContainer p$2$pNodes;

p$2$pNodes.Create$(2)$;

NodeContainer csmaNodes;

csmaNodes.Add$($p$2$pNodes.Get$(1))$;

csmaNodes.Create$($nCsma$)$;

PointToPointHelper pointToPoint;

pointToPoint.SetDeviceAttribute$("$DataRate$",$ StringValue$("5$Mbps$"))$;

pointToPoint.SetChannelAttribute$("$Delay$",$ StringValue$("2$ms$"))$;

NetDeviceContainer p$2$pDevices;

p$2$pDevices $=$ pointToPoint.Install$($p$2$pNodes$)$;

CsmaHelper csma;

csma.SetChannelAttribute$("$DataRate$",$ StringValue$("100$Mbps$"))$;

csma.SetChannelAttribute$("$Delay$",$ TimeValue$($NanoSeconds$(6560)))$;

NetDeviceContainer csmaDevices;

csmaDevices $=$ csma.Install$($csmaNodes$)$;

InternetStackHelper stack;

stack.Install$($p$2$pNodes.Get$(0))$;

stack.Install$($csmaNodes$)$;

Ipv$4$AddressHelper address;

address.SetBase$("10\mathrm{.}1\mathrm{.}1\mathrm{.}0","255\mathrm{.}255\mathrm{.}255\mathrm{.}0")$;

Ipv$4$InterfaceContainer p$2$pInterfaces;

p$2$pInterfaces $=$ address.Assign$($p$2$pDevices$)$;

address.SetBase$("10\mathrm{.}1\mathrm{.}2\mathrm{.}0","255\mathrm{.}255\mathrm{.}255\mathrm{.}0")$;

Ipv$4$InterfaceContainer csmaInterfaces;

csmaInterfaces $=$ address.Assign$($csmaDevices$)$;

UdpEchoServerHelper echoServer$(9)$;

ApplicationContainer serverApps $=$ echoServer.Install$($csmaNodes$.$Get$($nCsma$))$;

serverApps.Start$($Seconds$(1\mathrm{.}0))$;

serverApps.Stop$($Seconds$(10\mathrm{.}0))$;

UdpEchoClientHelper echoClient$($csmaInterfaces$.$GetAddress$($nCsma$),9)$;

echoClient.SetAttribute$("$MaxPackets$",$ UintegerValue$(1))$;

echoClient.SetAttribute$("$Interval$",$ TimeValue$($Seconds$(1\mathrm{.}0)))$;

echoClient.SetAttribute$("$PacketSize$",$ UintegerValue$(1024))$;

ApplicationContainer clientApps $=$ echoClient.Install$($p$2$pNodes.Get$(0))$;

clientApps.Start$($Seconds$(2\mathrm{.}0))$;

clientApps.Stop$($Seconds$(10\mathrm{.}0))$;

Ipv$4$GlobalRoutingHelper::PopulateRoutingTables$()$;

pointToPoint.EnablePcapAll$("$second$")$;

csma.EnablePcap$("$second$",$ csmaDevices.Get$(1),$ true$)$;

Simulator::Run$()$;

Simulator::Destroy$()$;

return $0$;

$\}$