异步客户端套接字不接收数据答案

【问题标题】：Asynchronous client socket not receiving data异步客户端套接字不接收数据
【发布时间】：2015-06-14 09:03:09
【问题描述】：

我尝试使用异步套接字通信来实现我的应用程序。它完美地连接并发送了请求，但我没有从服务器（Java 服务器）收到任何数据。套接字连接是

client.BeginConnect(hostname, port,
            new AsyncCallback(ConnectCallback), client);
connectDone.WaitOne();

  private static void ConnectCallback(IAsyncResult ar) {
    try {
        // Retrieve the socket from the state object.
        Socket client = (Socket) ar.AsyncState;

        // Complete the connection.
        client.EndConnect(ar);

        Console.WriteLine("Socket connected to {0}",
            client.RemoteEndPoint.ToString());

        // Signal that the connection has been made.
        connectDone.Set();
    } catch (Exception e) {
        Console.WriteLine(e.ToString());
    }
}

private static void Receive(Socket client)
{
    try
    {
        // Create the state object.
        StateObject state = new StateObject();
        state.workSocket = client;

        // Begin receiving the data from the remote device.
        client.BeginReceive(state.buffer, 0, StateObject.BufferSize, SocketFlags.None,
            new AsyncCallback(ReceiveCallback), client);
    }
    catch (Exception e)
    {
        Console.WriteLine(e.ToString());
    }
}

private static void ReceiveCallback(IAsyncResult ar)
{
    try
    {
        // Retrieve the state object and the client socket 
        // from the asynchronous state object.
        StateObject state = (StateObject)ar.AsyncState;
        Socket client = state.workSocket;

        // Read data from the remote device.
        int bytesRead = client.EndReceive(ar);
        Console.WriteLine(response);
        if (bytesRead > 0)
        {
            // There might be more data, so store the data received so far.
            state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead));

            // Get the rest of the data.
            client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                new AsyncCallback(ReceiveCallback), state);
        }
        else
        {
            // All the data has arrived; put it in response.
            if (state.sb.Length > 1)
            {
                response = state.sb.ToString();
            }
            // Signal that all bytes have been received.
            receiveDone.Set();
        }
    }
    catch (Exception e)
    {
        Console.WriteLine(e.ToString());
    }
}

任何帮助将不胜感激。

【问题讨论】：

好吧，ConnectCallback 不见了——还有：你怎么知道你已经连接了？您是否调试过此代码（在ReceiveCallback 中设置断点？） - 您是否尝试通过telnet 连接？当然，如果您开始接收并且那里还没有数据，您可能会看到 0 字节并停止一切
已连接 = true;此属性在调试模式下可见。我在receivecallback方法中设置了断点，但它没有执行。它一直在调试，直到beginreceive之后它从调试模式结束。而且我没有尝试过 telnet。
你也可以考虑检查一下stackoverflow.com/a/1388691/1537726

标签： c# sockets

【解决方案1】：

您的代码几乎没问题，但有一个严重的错误。在您的 BeginReceive 中，您将客户端套接字实例作为状态对象。在 ReceiveCallback 函数中，您将其转换为 StateObject 而不是套接字。这将导致控制台出现异常。

不过，由于这个错误，ReceiveCallback 函数开头的断点也会触发。你试过这个吗？无论如何都应该抛出异常。

如果断点没有触发，您应该独立检查是否真的从服务器发送了某些内容。当然，正如您所说，所有这些都假设连接有效。

【讨论】：