Sending and receiving UDP packets between two programs on the same computer

Question

Is it possible to get two separate programs to communicate on the same computer (one-way only) over UDP through localhost/127... by sharing the same port #?

We\'re

Answer 1

Here is the full code from the answers by Tarnay Kálmán and sipwiz:

The server code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

namespace UdpBroadcastTest
{
    class Program
    {
        static void Main(string[] args)
        {

            Console.WriteLine("Sender");
            // This constructor arbitrarily assigns the local port number.

            UdpClient udpClient = new UdpClient();
            udpClient.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
            udpClient.Connect("localhost", 11000);
            try
            {
                string message = String.Empty;
                do
                {
                    message = Console.ReadLine();
                    // Sends a message to the host to which you have connected.
                    Byte[] sendBytes = Encoding.ASCII.GetBytes(message);

                    udpClient.Send(sendBytes, sendBytes.Length);
                } while (message != String.Empty);

                udpClient.Close();
            }
            catch (Exception e)
            {
                Console.WriteLine(e.ToString());
            }

            Console.WriteLine("Press Any Key to Continue");
            Console.ReadKey();
        }
    }
}

The client code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading.Tasks;

namespace UdpReciever
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Receiver");
            // This constructor arbitrarily assigns the local port number.
            UdpClient udpClient = new UdpClient();
            udpClient.Client.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseAddress, true);
            udpClient.Client.Bind(new IPEndPoint(IPAddress.Any, 11000));
            try
            {
                //IPEndPoint object will allow us to read datagrams sent from any source.
                IPEndPoint RemoteIpEndPoint = new IPEndPoint(IPAddress.Any, 0);

                string message = String.Empty;
                do
                {

                    // Blocks until a message returns on this socket from a remote host.
                    Byte[] receiveBytes = udpClient.Receive(ref RemoteIpEndPoint);
                    message = Encoding.ASCII.GetString(receiveBytes);

                    // Uses the IPEndPoint object to determine which of these two hosts responded.
                    Console.WriteLine("This is the message you received: " +
                                                 message);
                    //Console.WriteLine("This message was sent from " +
                    //                            RemoteIpEndPoint.Address.ToString() +
                    //                            " on their port number " +
                    //                            RemoteIpEndPoint.Port.ToString());
                }
                while (message != "exit");
                udpClient.Close();
                //udpClientB.Close();

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

            Console.WriteLine("Press Any Key to Continue");
            Console.ReadKey();
        }
    }
}