Server client application running on same host machine with two different nic's ip.

Question

I am developing a server client application. In which server and client are running on same host machine. The host has two nic. Server is running on the ip of one of the nic and client has been bound to ip of the other nic. Respective codes of server and client is below.

Server Code:

namespace Server { class Program { static void Main(string[] args) { Console.WriteLine("The Server is Run And Wait .....");

        // Create Server Socket to recive
        try
        {
        IPAddress ipAddress = IPAddress.Parse("192.0.0.4");
        IPEndPoint ipLocalEndPoint = new IPEndPoint(ipAddress, 2700);
        TcpListener Ls = new TcpListener(ipLocalEndPoint);
         Ls.Start();
        while (true)
        {
            Socket soc = Ls.AcceptSocket();
            //soc.SetSocketOption(SocketOptionLevel.Socket,
            //        SocketOptionName.ReceiveTimeout,10000);
            try
            {
                Stream s = new NetworkStream(soc);
                StreamReader sr = new StreamReader(s);
                StreamWriter sw = new StreamWriter(s);
                sw.AutoFlush = true; // enable automatic flushing
                sw.WriteLine("{0} Number of employee",        ConfigurationManager.AppSettings.Count);
                while (true)
                {
                    string name = sr.ReadLine();
                    Console.WriteLine("name {0}",name);
                    sw.WriteLine("entered name {0}", name);
                    if (name == "" || name == null) break;
                    string job = ConfigurationManager.AppSettings[name];
                   if (job == null) job = "No such employee";
                    sw.WriteLine(job);
                }
                s.Close();
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            soc.Close();
        }

        }
        catch (Exception e)
        {
            Console.WriteLine(e.ToString());
           while (true)
               { }
        }

    }
}

}

Client Code

public class clnt {

public static void Main()
{
    try
    {
        IPAddress ipAddress = IPAddress.Parse("192.0.0.5");
        IPEndPoint ipLocalEndPoint = new IPEndPoint(ipAddress, 8000);
        TcpClient tcpclnt = new TcpClient(ipLocalEndPoint);
        Console.WriteLine("Connecting.....");
        tcpclnt.Connect("192.0.0.4", 2700);
        // use the ipaddress as in the server program

        Console.WriteLine("Connected");
        Console.Write("Enter the string to be transmitted : ");

        String str = Console.ReadLine();
        Stream stm = tcpclnt.GetStream();

        ASCIIEncoding asen = new ASCIIEncoding();
        byte[] ba = asen.GetBytes(str);
        Console.WriteLine("Transmitting.....");

        stm.Write(ba, 0, ba.Length);

        byte[] bb = new byte[100];
        int k = stm.Read(bb, 0, 100);

        for (int i = 0; i < k; i++)
            Console.Write(Convert.ToChar(bb[i]));

        tcpclnt.Close();
    }

    catch (SocketException e)
    {
        Console.WriteLine("Error..... " + e.ErrorCode);
    }
    while(true)
    {}
}

}

What code is doing not important. Only Connection part is point of concern.

When i am using constructor "TcpClient" without any parameter. I mean replace following three line of client IPAddress ipAddress = IPAddress.Parse("192.0.0.5"); IPEndPoint ipLocalEndPoint = new IPEndPoint(ipAddress, 8000); TcpClient tcpclnt = new TcpClient(ipLocalEndPoint); with TcpClient tcpclnt = new TcpClient(); It is working fine.

or

When client is running on different machine then also it is working fine.

Could you please be a more clear, what are you asking for ? what error you have. I don't understand what you want. — Alezis
@Alezis I am getting socket exception when client is at tcpclnt.Connect("192.0.0.4", 2700). — Indra Vikas

G DeMasters G DeMasters · Accepted Answer · 2018-02-15T19:11:00

For posterity: Using TcpClient()

allows the underlying service provider to assign the most appropriate local IP address and port number

(Source: https://msdn.microsoft.com/en-us/library/zc1d0e0f%28v=vs.110%29.aspx), which is why it works.

Assigning an endpoint by calling the TcpClient(IPEndpoint) overload forces it to a particular NIC, Address, and Port. If there is no network route from that IPEndpoint to the server's endpoint, the connection can not be made. It is generally considered bad practice to have two NICs on the same machine on the same network unless teaming is involved; the 192.0.0.4 and 192.0.0.5 is the issue, and putting the NICs on separate networks with a route between them would work with or without specifying the local endpoint on the client.

Server client application running on same host machine with two different nic's ip.

1 Answers