.NET Remoting example in C#

Form1.cs

/* NET Remoting Client */

using System;
using System.Collections;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Http;
using System.Runtime.Remoting.Channels.Ipc;
using System.Runtime.Remoting.Channels.Tcp;
using System.Security.Permissions;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace mpRemotingClient
{
    [SecurityPermission(SecurityAction.Demand)]
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        [Obsolete]
        private void cmdSum_Click(object sender, EventArgs e)
        {
            try 
            {
                var obj = (mpRemotingClass.RemoteOperations)Activator.GetObject(typeof(mpRemotingClass.RemoteOperations),
                               "tcp://localhost:8085/RemoteOperations");
 
                int x = Int32.Parse(txtValueOne.Text);
                int y = Int32.Parse(txtValueTwo.Text);
                txtResult.Text = (obj.sum(x, y)).ToString();
            }
            catch(Exception ex)
            {
                File.WriteAllText("mpRemotingClient.txt", ex.Message);
                MessageBox.Show(ex.Message);
            }
        }
    }
}

Program.cs

/* NET Remoting Server */

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Channels;
using System.Runtime.Remoting.Channels.Http;
using System.Runtime.Remoting.Channels.Tcp;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace mpRemotingServer
{
    class Program
    {
        [STAThread]
        static void Main(string[] args)
        {
            try
            {
                TcpServerChannel serverChannel = new TcpServerChannel(8085);
                ChannelServices.RegisterChannel(serverChannel, false);
                RemotingConfiguration.RegisterWellKnownServiceType(typeof
                               (mpRemotingClass.RemoteOperations), "RemoteOperations", WellKnownObjectMode.Singleton);

                Console.WriteLine("Listening on {0}",
                                  serverChannel.GetChannelUri());
                Console.WriteLine("Press the enter key to exit...");
                Console.ReadLine();
            }
            catch(Exception ex)
            {
                File.WriteAllText("mpRemotingServer.txt", ex.Message);
                MessageBox.Show(ex.Message);
            }
}
    }
}

RemoteOperations.cs

/* NET Remoting Object Definition */

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace mpRemotingClass
{
    public class RemoteOperations : MarshalByRefObject
    {
        public int sum(int a, int b)
        {
            return a + b;
        }
    }
}

On the server code, I have changed:

RemotingConfiguration.RegisterWellKnownServiceType(typeof (mpRemotingClass.RemoteOperations), "RemoteOperations", WellKnownObjectMode.Singleton);

// Changed to...
var remoteOperations = new mpRemotingClass.RemoteOperations(1);
RemotingServices.Marshal(remoteOperations, "RemoteOperations");

and the object definition is now:
public interface ICountingService
{
int Increment();
}

[Serializable]
public class RemoteOperations : MarshalByRefObject, ICountingService
{
    private static int _value = 0;

    public RemoteOperations(int startValue)
    {
        _value = startValue;
    }

    public int Increment()
    {
        // not threadsafe!
        _value++;
        return _value;
    }

    [System.Security.SecurityCritical]  // auto-generated
    public int sum(int a, int b)
    {
        return a + b;
    }
}

This still works fine on my test computer.