C#.NET Socket Programming: Connecting to remote computers

I have a typical server in my end and a friend using a client to connect to my IP/Port and he consistently receives the exception: "A connection attempt failed because the connected 开发者_开发问答party did not properly respond after a period of time, or established connection failed because connected host has failed to respond {MY_IP}:{MY_PORT}"—You don't need to know my IP.

The client and server, however, work fine on the loopback address (127.0.0.1). I also do not have any firewall nor is windows firewall active.

Server:

static void Main(string[] args)
        {
            Console.Title = "Socket Server";
            Console.WriteLine("Listening for messages...");

        Socket serverSock = new Socket(
            AddressFamily.InterNetwork,
            SocketType.Stream,
            ProtocolType.Tcp);

        IPAddress serverIP = IPAddress.Any;
        IPEndPoint serverEP = new IPEndPoint(serverIP, 33367);

        SocketPermission perm = new SocketPermission(NetworkAccess.Accept, TransportType.Tcp, "98.112.235.18", 33367);
        serverSock.Bind(serverEP);
        serverSock.Listen(10);

        while (true)
        {
            Socket connection = serverSock.Accept();

            Byte[] serverBuffer = new Byte[8];
            String message = String.Empty;

            while (connection.Available > 0)
            {
                int bytes = connection.Receive(
                    serverBuffer,
                    serverBuffer.Length,
                    0);

                message += Encoding.UTF8.GetString(
                    serverBuffer,
                    0,
                    bytes);
            }

            Console.WriteLine(message);
            connection.Close();
        }
    }

Client:

static void Main(string[] args)
    {
        // Design the client a bit
        Console.Title = "Socket Client";

        Console.Write("Enter the IP of the server: ");
        IPAddress clientIP = IPAddress.Parse(Console.ReadLine());
        String message = String.Empty;

        while (true)
        {
            Console.Write("Enter the message to send: ");
            // The messsage to send
            message = Console.ReadLine();

            IPEndPoint clientEP = new IPEndPoint(clientIP, 33367);

            // Setup the socket
            Socket clientSock = new Socket(
                AddressFamily.InterNetwork,
                SocketType.Stream,
                ProtocolType.Tcp);

            // Attempt to establish a connection to the server
            Console.Write("Establishing connection to the server... ");
            try
            {
                clientSock.Connect(clientEP);

                // Send the message
                clientSock.Send(Encoding.UTF8.GetBytes(message));
                clientSock.Shutdown(SocketShutdown.Both);
                clientSock.Close();
                Console.Write("Message sent successfully.\n\n");
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }
    }

Looks like it was an error on the client side with some firewall.

while (connection.Available > 0)
        {
            int bytes = connection.Receive(
                serverBuffer,
                serverBuffer.Length,
                0);

            message += Encoding.UTF8.GetString(
                serverBuffer,
                0,
                bytes);
        }

I don't know the reason(might be timing) but the number of available connections is always 0. Therefore the server does not receive the message sent by the client. Remove the while loop and your program will function without any problem. I tried it and it worked.

you need to add permission to allow socket to connect at specific endpoint using Assert() method.. Below server code may work,

    static void Main(string[] args)
    {
        Console.Title = "Socket Server";
        Console.WriteLine("Listening for messages...");

    Socket serverSock = new Socket(
        AddressFamily.InterNetwork,
        SocketType.Stream,
        ProtocolType.Tcp);

    IPAddress serverIP = IPAddress.Any;
    IPEndPoint serverEP = new IPEndPoint(serverIP, 33367);

    SocketPermission perm = new SocketPermission(NetworkAccess.Accept, TransportType.Tcp, "98.112.235.18", 33367);
    perm.Assert();
    serverSock.Bind(serverEP);
    serverSock.Listen(10);

    while (true)
    {
        Socket connection = serverSock.Accept();

        Byte[] serverBuffer = new Byte[8];
        String message = String.Empty;

        while (connection.Available > 0)
        {
            int bytes = connection.Receive(
                serverBuffer,
                serverBuffer.Length,
                0);

            message += Encoding.UTF8.GetString(
                serverBuffer,
                0,
                bytes);
        }

        Console.WriteLine(message);
        connection.Close();
    }
}