I am working my way through a book called C# Network Programming.

The example I'm working on creates a WinSoc Server and Client program. The code
is below.

When I use Telnet across my network to connect, it works fine. However,
when someone else outside the network attempts to connect, it fails.

Can someone help me understand what's going on?

using System;
using System.Net;
using System.Net.Sockets;
using System.Collections.Generic;
using System.Text;

namespace SimpleTcpSrvr
{
    class SimpleTcpSrvr
    {
        static void Main(string[] args)
        {
            // Define variables
            int recv;
            byte[] data = new byte[1024];
            IPEndPoint ipep = new IPEndPoint(IPAddress.Any, 9050);

            // Create a socket
            Socket newsock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

            // Bind the socket to the endpoint
            newsock.Bind(ipep);

            // List for up to 10 connections
            newsock.Listen(10);
            
            // Display a status message
            Console.WriteLine("Waiting for a client...");

            // Create a socket for the client
            Socket client = newsock.Accept();

            // Create an endpoint for the client
            IPEndPoint clientep = (IPEndPoint) client.RemoteEndPoint;

            // Display client connection information
            Console.WriteLine("Connected with [0] at port [1]", clientep.Address, clientep.Port);

            // Format the welcome text
            string welcome = "Welcome to my test server";

            // Convert the welcome text to a byte array
            data = Encoding.ASCII.GetBytes(welcome);

            // Send the message to the client
            client.Send(data, data.Length, SocketFlags.None);

            // Loop            
            while (true)
            {
                // Reformat the byte array
                data = new byte[1024];

                // Read in data from the client
                recv = client.Receive(data);

                // If a zero was received, then exit
                if (recv == 0)
                    break;

                // Write out the client data
                Console.WriteLine(Encoding.ASCII.GetString(data, 0, recv));

                // Echo the data back to the client
                client.Send(data, recv, SocketFlags.None);

            }

            // Display a disconnect message
            Console.WriteLine("Disconnected from [0]", clientep.Address);

            // Close the connections
            client.Close();
            newsock.Close();

        }
    }
}