title: Implement Simple TCP with NS3
body: <p>hi, 
  I'm new to NS3, I'm trying to modify first.cc to do TCP rather than UDP.
  I didn't get any error, but no data exchange happened as well.
  Could anyone help me on this?˜˜
  many thanks˜~
  here is the code: in the main:</p>
  
  <pre><code>    NS_LOG_INFO ("Creating Topology");
      Config::SetDefault ("ns3::OnOffApplication::PacketSize", UintegerValue (137));
  
      Config::SetDefault ("ns3::OnOffApplication::DataRate", StringValue ("14kb/s"));
    NodeContainer nodes;
    nodes.Create (2);
  //
    PointToPointHelper pointToPoint; 
    pointToPoint.SetDeviceAttribute ("DataRate", StringValue ("100Mbps"));
    pointToPoint.SetChannelAttribute ("Delay", StringValue ("20ms"));
  //
    NetDeviceContainer devices;
    devices = pointToPoint.Install (nodes);
    InternetStackHelper stack;
    stack.Install (nodes);
      Ipv4AddressHelper address;
      address.SetBase ("109.11.12.0", "255.255.255.0");//address setting
  
      Ipv4InterfaceContainer interfaces = address.Assign (devices);
  
      OnOffHelper onOffHelper ("ns3::TcpSocketFactory", Address
                         (InetSocketAddress (Ipv4Address ("255.255.255.0"), 10)));
      onOffHelper.SetAttribute ("OnTime", StringValue ("ns3::ConstantRandomVariable[Constant=1]"));
      onOffHelper.SetAttribute ("OffTime", StringValue ("ns3::ConstantRandomVariable[Constant=0]"));
  
      onOffHelper.SetAttribute ("DataRate",StringValue ("2Mbps"));
      onOffHelper.SetAttribute ("PacketSize",UintegerValue(2000));
      ApplicationContainer app = onOffHelper.Install (nodes.Get (0));
  
      // Start the application
      app.Start (Seconds (10.0));
      app.Stop (Seconds (100.0));
  
      // Create an optional packet sink to receive  packets
  
      PacketSinkHelper sink ("ns3::TcpSocketFactory",Address
                             (InetSocketAddress (Ipv4Address::GetAny (), 10)));
      app = sink.Install (nodes.Get(1));
      app.Start (Seconds (1.0));
      app.Stop (Seconds (100.0));
  
      pointToPoint.EnablePcapAll ("testtcp");
  </code></pre>