使用异步套接字接收数据答案

【问题标题】：use asynchronus socket to receive data使用异步套接字接收数据
【发布时间】：2015-04-16 05:37:02
【问题描述】：

我使用 2 种方式通过连接到 IP 地址的套接字接收数据。

同步接收。
异步接收。

使用同步接收，我可以在不到 1 秒的时间内从服务器获得所有响应。但是使用异步接收，接收所有响应需要 30 多秒。

代码如下：

 class StateObject
{
    // Client socket.
    public Socket workSocket = null;
    // Size of receive buffer.
    public const int BufferSize = 256;
    // Receive buffer.
    public byte[] buffer = new byte[BufferSize];
    // Received data string.
    public StringBuilder sb = new StringBuilder();
}

    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, 0,
                new AsyncCallback(ReceiveCallback), state);
        }
        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);
            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.ReceiveTimeout = 500;
                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)
        {
            MessageBox.Show(e.ToString());
        }
    }

【问题讨论】：

你有什么问题？
我认为问题很明确（为什么延迟） - 我不是 100% 确定，但你能用你的代码测试 SocketFlags.Partial 标志吗？
我怎样才能像同步方法一样快地接收数据？
if (bytes Read > 0) ... else { ... receiveDone.Set(); } 看起来也很可疑——你需要一个 0 字节的读取来设置它（这很可能只有在另一端断开连接时才会发生——或者我猜是这样）
根据我的上一条评论和您的代码，您似乎可以在阅读任何内容后立即设置receiveDone（您只需要 1 个 ASCII 字符 - 1 个字节） - 那你为什么不@ 987654325@ 就在state.sb.Append(...) 之后）？

标签： c# sockets beginreceive

【解决方案1】：

您应该在将当前字符串附加到缓冲区后检查您的值，以便处理消息并删除 client.ReceiveTimeout = 500;我认为这需要时间：

        if (bytesRead > 0)
        {
            state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead));

            response = state.sb.ToString();
            if (response.IndexOf("<EOF>") != -1)
            {
                state.sb.Clear();
                receiveDone.Set();
            }
            else
            {
                client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
                    new AsyncCallback(ReceiveCallback), state);
            }
        }

这仅适用于一条消息，对于实时多条消息，我认为您应该尝试不同的方法。

【讨论】：