C＃.NET套接字编程：连接到远程计算机

Question

我的终端是一台典型的服务器，一个朋友正在使用客户端连接到我的IP /端口，他始终收到以下异常消息：“连接尝试失败，因为连接的用户在一段时间后未正确响应，或者建立了连接因连接的主机未能响应{MY_IP}：{MY_PORT}“而失败-您不需要知道我的IP。

但是，客户端和服务器在环回地址（127.0.0.1）上可以正常工作。 我也没有任何防火墙，Windows防火墙也没有激活。

服务器：

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();
        }
    }

客户：

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);
            }
        }
    }

Answer 1

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

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

我不知道原因（可能是时间问题），但是可用连接数始终为0。因此，服务器未收到客户端发送的消息。 删除while循环，您的程序将正常运行。 我尝试了，它奏效了。

Answer 2

看起来这是带有某些防火墙的客户端错误。

Answer 3

您需要添加权限以允许套接字使用Assert（）方法在特定端点进行连接。以下服务器代码可能有效，

    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();
    }
}