套接字编程c# /客户端-服务器通信

Question

我试图在.NET中制作两个通过网络进行通信的程序(在控制台应用程序中)(代码是从下面的视频中找到的，我只是试着在修改代码之前使代码正常工作)。原谅我，我不是一个有经验的程序员。

我有一个服务器和一个客户端，当我在我的计算机上(本地)运行这两个服务器时，它们都能很好地工作。我可以将多个客户端连接到服务器，发送请求并获得响应。当我在一台计算机上运行服务器，在另一台计算机上运行客户机时，我试图通过互联网连接，我面临着这个问题。

我可以连接到服务器，但通信不工作，没有数据交换时，试图请求时间为例。我认为问题主要来自网络本身，而不是代码。

以下是服务器的代码：

class Program
{
    private static Socket _serverSocket;
    private static readonly List<Socket> _clientSockets = new List<Socket>();
    private const int _BUFFER_SIZE = 2048;
    private const int _PORT = 50114;
    private static readonly byte[] _buffer = new byte[_BUFFER_SIZE];

    static void Main()
    {
        Console.Title = "Server";
        SetupServer();
        Console.ReadLine(); // When we press enter close everything
        CloseAllSockets();
    }



    private static void SetupServer()
    {
      //  IPAddress addip = GetBroadcastAddress();
        Console.WriteLine("Setting up server...");
        _serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        _serverSocket.Bind(new IPEndPoint(IPAddress.Any , _PORT));
        _serverSocket.Listen(5);
        _serverSocket.BeginAccept(AcceptCallback, null);
        Console.WriteLine("Server setup complete");
    }

    /// <summary>
    /// Close all connected client (we do not need to shutdown the server socket as its connections
    /// are already closed with the clients)
    /// </summary>
    private static void CloseAllSockets()
    {
        foreach (Socket socket in _clientSockets)
        {
            socket.Shutdown(SocketShutdown.Both);
            socket.Close();
        }

        _serverSocket.Close();
    }

    private static void AcceptCallback(IAsyncResult AR)
    {
        Socket socket;

        try
        {
            socket = _serverSocket.EndAccept(AR);
        }
        catch (ObjectDisposedException) // I cannot seem to avoid this (on exit when properly closing sockets)
        {
            return;
        }

       _clientSockets.Add(socket);
       socket.BeginReceive(_buffer, 0, _BUFFER_SIZE, SocketFlags.None, ReceiveCallback, socket);
       Console.WriteLine("Client connected, waiting for request...");
       _serverSocket.BeginAccept(AcceptCallback, null);
    }

    private static void ReceiveCallback(IAsyncResult AR)
    {
        Socket current = (Socket)AR.AsyncState;
        int received;

        try
        {
            received = current.EndReceive(AR);
        }
        catch (SocketException)
        {
            Console.WriteLine("Client forcefully disconnected");
            current.Close(); // Dont shutdown because the socket may be disposed and its disconnected anyway
            _clientSockets.Remove(current);
            return;
        }

        byte[] recBuf = new byte[received];
        Array.Copy(_buffer, recBuf, received);
        string text = Encoding.ASCII.GetString(recBuf);
        Console.WriteLine("Received Text: " + text);

        if (text.ToLower() == "get time") // Client requested time
        {
            Console.WriteLine("Text is a get time request");
            byte[] data = Encoding.ASCII.GetBytes(DateTime.Now.ToLongTimeString());
            current.Send(data);
            Console.WriteLine("Time sent to client");
        }
        else if (text.ToLower() == "exit") // Client wants to exit gracefully
        {
            // Always Shutdown before closing
            current.Shutdown(SocketShutdown.Both);
            current.Close();
            _clientSockets.Remove(current);
            Console.WriteLine("Client disconnected");
            return;
        }
        else
        {
            Console.WriteLine("Text is an invalid request");
            byte[] data = Encoding.ASCII.GetBytes("Invalid request");
            current.Send(data);
            Console.WriteLine("Warning Sent");
        }

        current.BeginReceive(_buffer, 0, _BUFFER_SIZE, SocketFlags.None, ReceiveCallback, current);
    }
}

这里是客户端代码：

class Program
{
    private static readonly Socket _clientSocket = new Socket
        (AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

    private const int _PORT = 50114;

    static void Main()
    {
        Console.Title = "Client";
        ConnectToServer();
        RequestLoop();
        Exit();
    }

    private static void ConnectToServer()
    {
        int attempts = 0;

        while (!_clientSocket.Connected)
        {
            try
            {
                attempts++;
                Console.WriteLine("Connection attempt " + attempts);
                _clientSocket.Connect("IpAddr", _PORT);
            }
            catch (SocketException) 
            {
                Console.Clear();
            }
        }

        Console.Clear();
        Console.WriteLine("Connected");
    }

    private static void RequestLoop()
    {
        Console.WriteLine(@"<Type ""exit"" to properly disconnect client>");

        while (true)
        {
            SendRequest();
            ReceiveResponse();
        }
    }

    /// <summary>
    /// Close socket and exit app
    /// </summary>
    private static void Exit()
    {
        SendString("exit"); // Tell the server we re exiting
        _clientSocket.Shutdown(SocketShutdown.Both);
        _clientSocket.Close();
        Environment.Exit(0);
    }

    private static void SendRequest()
    {
        Console.Write("Send a request: ");
        string request = Console.ReadLine();
        SendString(request);

        if (request.ToLower() == "exit")
        {
            Exit();
        }
    }

    /// <summary>
    /// Sends a string to the server with ASCII encoding
    /// </summary>
    private static void SendString(string text)
    {
        byte[] buffer = Encoding.ASCII.GetBytes(text);
        _clientSocket.Send(buffer, 0, buffer.Length, SocketFlags.None);
    }

    private static void ReceiveResponse()
    {
        var buffer = new byte[2048];
        int received = _clientSocket.Receive(buffer, SocketFlags.None);
        if (received == 0) return;
        var data = new byte[received];
        Array.Copy(buffer, data, received);
        string text = Encoding.ASCII.GetString(data);
        Console.WriteLine(text);
    }
}
 static void Main()
    {
        Console.Title = "Client";
        ConnectToServer();
        RequestLoop();
        Exit();
    }

    private static void ConnectToServer()
    {
        int attempts = 0;

        while (!_clientSocket.Connected)
        {
            try
            {
                attempts++;
                Console.WriteLine("Connection attempt " + attempts);
                _clientSocket.Connect("IpAddr", _PORT);
            }
            catch (SocketException) 
            {
                Console.Clear();
            }
        }

        Console.Clear();
        Console.WriteLine("Connected");
    }

"IpAddr“是路由器的公共IP的占位符。

这是我当前代码所基于的视频：https://www.youtube.com/watch?v=xgLRe7QV6QI

我直接从其中提取了代码(您可以在描述中链接的站点上找到这两个代码文件)。

我运行服务器，它正在等待连接。然后运行试图连接到服务器的客户端。我连接并在服务器上显示成功的连接。然后，客户端发送一个类似于“获取时间”的请求，服务器应该捕获它并作出响应：

 byte[] data = Encoding.ASCII.GetBytes(DateTime.Now.ToLongTimeString());
 current.Send(data);

回到网络端：

下面是我尝试过的所有事情的清单，这是问题的主要原因，在寻找了大约一整天的解决方案之后：

• 我已经为路由器提供了一个静态的公共IP (因此公共IP永远不会改变)。尽管如此，我还是在noip.com上创建了一个动态dns。
• 我给服务器运行的计算机提供了一个静态租约，因此它始终具有相同的本地ip。
• 我在windows防火墙中创建了规则，以确保我使用的端口是打开的。我在两台电脑上都做了这件事，试图沟通。
• 我转发了路由器上的端口，使其指向服务器运行的计算机的本地ip。(我尝试了很多不同的港口，没有机会)
• 我尝试激活路由器上的"DMZ“，但很可能不是一个解决方案
• 我尝试创建一个ASP.NET网站，其中页面返回一个字符串，用IIS7.5发布它并设置它。在本地主机上工作，但使用“xx.xx:PORT/default/index”这样的公共ip，我会得到一个错误。然而，它在错误中显示了网站名称。此外，当使用计算机的本地IP时，它也不能工作(类似于192.168.1.180)。

谢谢你的帮助。

Answer 1

我学到了消息框架，谢谢CodeCaster。

对于那些对此感到好奇的人，我发现了一个有趣的链接：http://blog.stephencleary.com/2009/04/message-framing.html

但在尝试更改代码之前，我在AWS vps上运行服务器，它立即工作，问题可能是从我的isp或我的路由器开始的。我只是想知道它如何工作，而不处理消息框架。