In This article we see how to find IP Address of one system,This is useful for Network programming Developer. so lets see step by step
  1. Step- open VS studio 2008/2010 ----Console Application
  2. First add network related Namespace like

    Using System.Net;

    And Using System.Net,NetworkInformation;
  3. And write follow code

    {
     string hostname = Dns.GetHostName();
    Console.WriteLine(hostname);
    IPAddress[] ipaddress = Dns.GetHostAddresses(hostname);

    Console.WriteLine(ipaddress[1]);

    }

    Above code is to find IP address of one system if you want communicate between two system throw IP address in LAN then use follow code

    {
     Ping pingSender = new Ping();
    PingOptions options = new PingOptions();

    options.DontFragment = true;

    // Create a buffer of 32 bytes of data to be transmitted.
     string data = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
    byte[] buffer = Encoding.ASCII.GetBytes(data);
    int timeout = 120;
    PingReply reply = pingSender.Send(ipaddress[1], timeout, buffer, options);
    if (reply.Status == IPStatus.Success)
    {
    Console.WriteLine("Address: {0}", reply.Address.ToString());
    Console.WriteLine("RoundTrip time: {0}", reply.RoundtripTime);
    Console.WriteLine("Time to live: {0}", reply.Options.Ttl);
    Console.WriteLine("Don't fragment: {0}", reply.Options.DontFragment);
    Console.WriteLine("Buffer size: {0}", reply.Buffer.Length);
    }

    }

  4. Run this code and give command ping and checked whether communication is going or not.