C# 聊天程序

Question

When I use the local machine to host and connect to it works 100% but when I try it real-time(server prog sitting on actual server and client on other machine) it doesn't work. I'm getting the "No connection could be made because the target machine actively refused it". I checked that it's actively listen(and too correct port on server) -it is, disabled all firewalls including router[it also has a rule set to allow it beside trying disabling]-didn't fix.

Could this be a internal networking issue? Like it's just not liking trying to connect to a local machine? I'm clueless and no other exceptions are being thrown or anything.

Server's Code

IPAddress ip = IPAddress.Parse("127.0.0.1");
        Int32 port = 9818;
        TcpListener server = new TcpListener(ip,port);
        TcpClient client;try
        {
            server.Start();
            Console.WriteLine("Server Started..");


        }
        catch (Exception exp)
        {
            Console.WriteLine(exp.Message);

        }

        while (true)
        {
            client = server.AcceptTcpClient();

            byte[] recieveBuffer = new byte[100];
            byte[] sendBuffer = new byte[100];
            NetworkStream stream = client.GetStream();

            stream.Read(recieveBuffer, 0, recieveBuffer.Length);

            StringBuilder msg = new StringBuilder();
            foreach (byte b in recieveBuffer)
            {
                if (b.Equals(00))
                {
                    break;
                }
                else
                    msg.Append(Convert.ToChar(b).ToString());
            }

            int byteCount = Encoding.ASCII.GetByteCount(msg.ToString());
            byte[] sendData = new byte[byteCount];

            stream.Write(sendData, 0, sendData.Length);
            Console.WriteLine(msg);}//End while

And the client is..

public Int32 port = 9818;
    public TcpClient client;
    public string serverIP = "10.0.0.20";
    //public string serverIP = "localhost"; //For testings
    private void btnLogin_Click(object sender, EventArgs e)
    {
        try
        {
            client = new TcpClient(serverIP, port);

            //Clean up space
            int byteCountU = Encoding.ASCII.GetByteCount(txtUser.Text);
            int byteCountP = Encoding.ASCII.GetByteCount(txtPassword.Text);

            //Send
            byte[] sendDataU = new byte[byteCountU];
            byte[] sendDataP = new byte[byteCountP];

            //Greating should be formated on server's end to not ruin user and password sending
            sendDataU = Encoding.ASCII.GetBytes(txtUser.Text);
            sendDataP = Encoding.ASCII.GetBytes(txtPassword.Text);

            NetworkStream stream = client.GetStream();

            stream.Write(sendDataU, 0, sendDataU.Length);

            //Close
            stream.Close();
            client.Close();

And sorry, this formating interface is anonying best i could do

Answer 1

This is a networking problem, not a programming one.

As a general rule, the Network Classes do not care if the other end is on the same computer, same swtich or the Voyager 2 probe. Making a path there is a Networking Problem, not a programming one.

My best guess is for something like the Windows Firefall being a bit to agressive.

As a side note: Exception handling is a pet peeve of mine, and yours has issues. Here are two articles on the thematic that I link often:

• https://blogs.msdn.microsoft.com/ericlippert/2008/09/10/vexing-exceptions/
• https://www.codeproject.com/Articles/9538/Exception-Handling-Best-Practices-in-NET

Answer 2

You set your server to listen only on localhost (127.0.0.1). It means only local connections are allowed and resolved, so firewall will be disabled on those connections and you can ignore it most of the time. It is usefull when you debug your application OR you have interprocess communication on same machine.

To listen to incoming connections from other machines, you should have sufficient privelegies and set your server address to 0.0.0.0, which means "listen to all external connections".