c# – 多个客户端的异步TCP服务器

2023年5月4日 189次阅读

我有一个TCP服务器,它可以异步侦听传入连接.如果只连接一个客户端,一切正常.但是,如果有两个或更多连接,则服务器不会收到第一条消息.当我调试ReceiveCallback函数时,我可以看到服务器获取消息的长度而不是数据.即如果我连接两个客户端并尝试发送第一条消息：“hello”,服务器获取：received = 5; buffer = / 0/0/0/0/0,因此不显示任何内容.在同一客户端的第二条消息中,服务器获取数据.

这就是我的服务器的样子：

        private void StartServer()
    {
        try
        {
            serverSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            serverSocket.Bind(new IPEndPoint(IPAddress.Any, 3333));
            serverSocket.Listen(100);
            serverSocket.BeginAccept(new AsyncCallback(AcceptCallback), null);   

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }


     private void AcceptCallback(IAsyncResult ar)
    {
        try
        {
            Socket clientSocket = serverSocket.EndAccept(ar); 
            clientSocketList.Add(clientSocket);
            AppendToTextBox("ClientConnected");
            clientSocket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveCallback), clientSocket);
            serverSocket.BeginAccept(new AsyncCallback(AcceptCallback), null);

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }


        private void ReceiveCallback(IAsyncResult ar)
    {
        try
        {
            int received = 0;
            Socket current = (Socket)ar.AsyncState;
            received = current.EndReceive(ar);
            byte[] data = new byte[received];

            if (received == 0)
            {
                return;
            }

            Array.Copy(buffer, data, received);
            string text = Encoding.ASCII.GetString(data);

            AppendToTextBox(text);
            buffer = null;
            Array.Resize(ref buffer, current.ReceiveBufferSize);

            current.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveCallback), current);
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }

最佳答案 请参阅
http://msdn.microsoft.com/en-us/library/dxkwh6zw.aspx的示例

您希望更改代码,以便每次调用BeginReceive时它都会分配一个新缓冲区：

        Socket clientSocket = serverSocket.EndAccept(ar); 
        clientSocketList.Add(clientSocket);
        AppendToTextBox("ClientConnected");
        var buffer = new byte[BUFFER_LENGTH];  // <---
        clientSocket.BeginReceive(buffer, 0, buffer.Length, SocketFlags.None, new AsyncCallback(ReceiveCallback), clientSocket);
        serverSocket.BeginAccept(new AsyncCallback(AcceptCallback), null);

每个客户端必须有一个缓冲区.否则,一个客户端可以覆盖另一个客户端使用的缓冲区.

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