Socket programming in ns3 with python

Question

I wrote a code in python for doing socket programming in ns3. In my code I can see the source sends a packet to the sink, but sink will not respond to receive the packet (Actually I believe "RecPkt" method is not executing, but I don't know why). Here is the part of my code related to methods for sending and receiving packets:

packetsize = 64 #bytes
pktcount = 2
pktinterval = 0.25 #seconds 


def RecPkt(socket):
    while socket.Recv():
        print "Received one packet!"

def SndPkt(socket, packetsize, pktcount, pktinterval):
    if pktcount > 0: 
        socket.Send(ns.network.Packet(packetsize)) 
        ns.core.Simulator.Schedule(pktinterval, SndPkt, socket, packetsize, pktcount-1, pktinterval)
        print "Sending one packet!"
    else:
        socket.Close() 

---

Here is the code for defining the source and the sink:

appSource = ns.network.NodeList.GetNode(1)
appSink = ns.network.NodeList.GetNode(20)

remoteAddr = appSink.GetObject(ns.internet.Ipv4.GetTypeId()).GetAddress(1,0).GetLocal()

sink = ns.network.Socket.CreateSocket(appSink, ns.core.TypeId.LookupByName("ns3::UdpSocketFactory"))
sink.Bind(ns.network.InetSocketAddress(ns.network.Ipv4Address.GetAny(), 80))
sink.SetRecvCallback(RecPkt)

source = ns.network.Socket.CreateSocket(appSource, ns.core.TypeId.LookupByName("ns3::UdpSocketFactory"))
source.Connect(ns.network.InetSocketAddress(remoteAddr, port))

---

here is the last part of the code relating to repeating sending the packet for each interval. For example if the pktcount=2 then the source will send two packets:

ns.core.Simulator.Schedule(ns.core.Seconds(30.0), SndPkt, source, packetsize, pktcount, pktinterval)

print "Run Simulation."
ns.core.Simulator.Stop(ns.core.Seconds(stopTime))
ns.core.Simulator.Run()
ns.core.Simulator.Destroy()

---

Here is the result that I am getting:

Configure Tracing.
Run Simulation.
Sending one packet!
Sending one packet!
root@far-System:

Would you please help me where is my mistake?

Thanks a lot

Answer 1

Thanks for the question! Even though there is no answer it gave me hope that NS-3 sockets might work with Python and therefore made me investigate further.

I cannot directly help you with your problem (answer to the comment by Mateus Sousa about port number might be helpful), but based on your code and some C++ examples I have created the following working example. I hope you can benefit from it and find the bug in your implementation.

import ns.applications
import ns.core
import ns.internet
import ns.network
import ns.point_to_point

nodes = ns.network.NodeContainer()
nodes.Create(2)

pointToPoint = ns.point_to_point.PointToPointHelper()
pointToPoint.SetDeviceAttribute("DataRate", ns.core.StringValue("5Mbps"))
pointToPoint.SetChannelAttribute("Delay", ns.core.StringValue("2000ms"))

devices = pointToPoint.Install(nodes)

stack = ns.internet.InternetStackHelper()
stack.Install(nodes)

address = ns.internet.Ipv4AddressHelper()
address.SetBase(ns.network.Ipv4Address("10.1.1.0"),
                ns.network.Ipv4Mask("255.255.255.0"))

interfaces = address.Assign(devices)

source = ns.network.Socket.CreateSocket(
    nodes.Get(0),
    ns.core.TypeId.LookupByName("ns3::UdpSocketFactory")
)


sink = ns.network.Socket.CreateSocket(
    nodes.Get(1),
    ns.core.TypeId.LookupByName("ns3::UdpSocketFactory")
)


def send_packet(socket):
    print("sending", ns.core.Simulator.Now())
    socket.Send(ns.network.Packet(5))


def rcv_packet(socket):
    print("received", ns.core.Simulator.Now())


sink.SetRecvCallback(rcv_packet)


sink_address = ns.network.InetSocketAddress(interfaces.GetAddress(1), 4477)
any_address = ns.network.InetSocketAddress(
    ns.network.Ipv4Address.GetAny(), 4477
)

sink.Bind(any_address)
source.Connect(sink_address)

ns.core.Simulator.Schedule(
    ns.core.Seconds(0.0), send_packet, source,
)

ns.core.Simulator.Run()
ns.core.Simulator.Destroy()