我正在尝试利用 MSDN 的异步客户端套接字代码示例来连接和控制一些家用设备。据我了解，示例代码的ReceiveCallback方法使用 EventWaitHandle ManualResetEvent的实例和方法receiveDone.WaitOne()来保持当前线程的处理，直到线程接收到所有套接字数据已从远程设备传输的信号. 传输完所有套接字数据后（套接字数据为空且bytesRead = 0），Waithandle 被移除，应用程序继续处理。
不幸的是，通过逐步执行代码，似乎在客户端最后一次从远程设备返回数据之后，ReceiveCallback永远不会返回查看数据队列是否为空（即 bytesRead = 0），因此永远不会在ReceiveCallback中进入“else”条件，其中ManualResetEvent的状态将被重置并且应用程序将继续处理。因此，由于它永远不会进入“else”条件，ManualResetEvent永远不会重置并且应用程序会冻结。
虽然我可以从代码中删除“receiveDone.WaitOne()”方法——允许执行而无需等待ManualResetEvent通知已收到所有数据；这会从设备返回一个通常不完整的数据字符串。
我是否错误地使用了此代码示例？有没有人以前见过这个或有任何关于如何解决这个问题的经验？
2012 年 7 月 14 日 - 更新：在进一步测试 MSDN 的异步客户端套接字示例后，很明显ReceiveCallback实际上重新轮询端口，并且只有在释放套接字时才满足“bytesRead = 0”条件（即客户端。关机（SocketShutdown.Both）；client.Close（）；）。如果我理解正确，这意味着必须关闭连接才能通过 receiveDone.WaitOne() 方法。如果连接被关闭以满足 WaitOne() Waithandle，它完全违背了应用程序的目的，因为我一直希望保持连接打开，以便应用程序可以监听设备更新，这些更新会不断发生。
2012 年 7 月 16 日 - 更新：我已写信给Microsoft 技术支持，他们回复说“我们正在研究这个问题。我们可能需要一些时间才能回复您。” 因此，目前似乎无法通过按摩此代码来解决此挑战。
如果没有异步客户端套接字示例代码作为编写异步通信程序的基础，请问是否有人可以建议一个更可靠的替换例程？ 共有三台设备，每台都有自己的 IP 地址和端口号。因此，如果可以使用一个类，为每个设备创建一个实例，那将是理想的。此外，端口必须保持打开状态才能接收设备不断发送的自发更新。最后，更新没有结束字符或定义的长度表示消息传输完成，因此例程必须不断轮询端口以获取可用数据。 任何意见或建议将不胜感激。
2012 年 7 月 18 日 - 解决方法：在花费大量时间尝试使MSDN 的异步客户端套接字代码示例正常工作后，很明显我必须寻找其他地方才能让程序持续识别设备响应。为了挽救其他人的脑损伤，我已经包含了我使用的解决方法，到目前为止似乎效果很好。如果有人有任何建议，请不要犹豫，添加到这个问题！
//
// ORIGINAL CODE ATTEMPT
//
public static Socket LutronClient;
public static String LutronResponse = String.Empty;
private const int LutronPort = 4999;
private const string LutronIP = "192.168.1.71";
private static ManualResetEvent LutronConnectDone = new ManualResetEvent(false);
private static ManualResetEvent LutronSendDone = new ManualResetEvent(false);
private static ManualResetEvent LutronReceiveDone = new ManualResetEvent(false);
private static void StartLutronClient()
{
try
{
var lutronIPAddress = IPAddress.Parse(LutronIP);
var lutronRemoteEP = new IPEndPoint(lutronIPAddress, LutronPort);
LutronClient = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
LutronClient.BeginConnect(lutronRemoteEP, LutronConnectCallback, LutronClient);
LutronConnectDone.WaitOne();
LutronSend(LutronClient, "sdl,14,100,0,S2\x0d");
LutronSendDone.WaitOne();
LutronReceive(LutronClient);
LutronReceiveDone.WaitOne(new TimeSpan(5000));
MessageBox.Show("Response received from Lutron: " + LutronResponse);
txtBoxLutron.Text = LutronResponse;
LutronClient.Shutdown(SocketShutdown.Both);
LutronClient.Close();
}
catch (Exception e) { MessageBox.Show(e.ToString()); }
}
private static void LutronConnectCallback(IAsyncResult lutronAr)
{
try
{
var lutronClient = (Socket)lutronAr.AsyncState;
lutronClient.EndConnect(lutronAr);
LutronConnectDone.Set();
}
catch (Exception e) { MessageBox.Show(e.ToString()); }
}
private static void LutronReceive(Socket lutronClient)
{
try
{
var lutronState = new LutronStateObject { LutronWorkSocket = lutronClient };
lutronClient.BeginReceive(lutronState.LutronBuffer, 0, LutronStateObject.BufferSize, 0, new AsyncCallback(LutronReceiveCallback), lutronState);
}
catch (Exception e) { MessageBox.Show(e.ToString()); }
}
private static void LutronReceiveCallback(IAsyncResult lutronAR)
{
try
{
var lutronState = (LutronStateObject)lutronAR.AsyncState;
var lutronClient = lutronState.LutronWorkSocket;
var bytesRead = lutronClient.EndReceive(lutronAR);
if (bytesRead > 0)
{
lutronState.LutronStringBuilder.AppendLine(Encoding.ASCII.GetString(lutronState.LutronBuffer, 0, bytesRead));
lutronClient.BeginReceive(lutronState.LutronBuffer, 0, LutronStateObject.BufferSize, 0, new AsyncCallback(LutronReceiveCallback), lutronState);
}
else
{
if (lutronState.LutronStringBuilder.Length > 0) { LutronResponse = lutronState.LutronStringBuilder.ToString(); }
LutronReceiveDone.Set();
}
}
catch (Exception e) { MessageBox.Show(e.ToString()); }
}
public static void LutronSend(Socket client, String data)
{
var byteData = Encoding.ASCII.GetBytes(data);
client.BeginSend(byteData, 0, byteData.Length, 0, LutronSendCallback, client);
}
private static void LutronSendCallback(IAsyncResult ar)
{
try
{
var client = (Socket)ar.AsyncState;
var bytesSent = client.EndSend(ar);
LutronSendDone.Set();
}
catch (Exception e) { MessageBox.Show(e.ToString()); }
}
public class LutronStateObject
{
public Socket LutronWorkSocket;
public const int BufferSize = 256;
public byte[] LutronBuffer = new byte[BufferSize];
public StringBuilder LutronStringBuilder = new StringBuilder();
}
}
这是我使用的解决方法：
//
// WORK-AROUND
//
using System;
using System.Windows.Forms;
namespace _GlobalCacheInterface
{
public partial class GlobalCacheDataScreen : Form
{
//Interface objects
private static GC_Interface _lutronInterface;
private const int LutronPort = 4999;
private const string LutronIP = "192.168.1.71";
delegate void ThreadSafeLutronCallback(string text);
private static GC_Interface _elanInterface;
private const int ElanPort = 4998;
private const string ElanIP = "192.168.1.70";
delegate void ThreadSafeElanCallback(string text);
private static GC_Interface _tuneSuiteInterface;
private const int TuneSuitePort = 5000;
private const string TuneSuiteIP = "192.168.1.70";
delegate void ThreadSafeTuneSuiteCallback(string text);
public GlobalCacheDataScreen()
{
InitializeComponent();
_lutronInterface = new GC_Interface(LutronIP, LutronPort);
_elanInterface = new GC_Interface(ElanIP, ElanPort);
_tuneSuiteInterface = new GC_Interface(TuneSuiteIP, TuneSuitePort);
// Create event handlers to notify application of available updated information.
_lutronInterface.DataAvailable += (s, e) => ThreadSafeTxtBoxLutron(_lutronInterface._returnString);
_elanInterface.DataAvailable += (s, e) => ThreadSafeTxtBoxElan(_elanInterface._returnString);
_tuneSuiteInterface.DataAvailable += (s, e) => ThreadSafeTxtBoxTuneSuite(_tuneSuiteInterface._returnString);
_lutronInterface.Connected += (s, e) => UpdateUI();
_elanInterface.Connected += (s, e) => UpdateUI();
_tuneSuiteInterface.Connected += (s, e) => UpdateUI();
UpdateUI();
}
private void UpdateUI()
{
_buttonConnectToLutron.Enabled = !_lutronInterface._isConnected;
_buttonConnectToElan.Enabled = !_elanInterface._isConnected;
_buttonConnectToTuneSuite.Enabled = !_tuneSuiteInterface._isConnected;
_buttonDisconnectFromLutron.Enabled = _lutronInterface._isConnected;
_buttonDisconnectFromElan.Enabled = _elanInterface._isConnected;
_buttonDisconnectFromTuneSuite.Enabled = _tuneSuiteInterface._isConnected;
string connectLutronStatus = _lutronInterface._isConnected ? "Connected" : "Not Connected";
string connectElanStatus = _elanInterface._isConnected ? "Connected" : "Not Connected";
string connectTuneSuiteStatus = _tuneSuiteInterface._isConnected ? "Connected" : "Not Connected";
_textBoxLutronConnectStatus.Text = connectLutronStatus;
_textBoxElanConnectStatus.Text = connectElanStatus;
_textBoxTuneSuiteConnectStatus.Text = connectTuneSuiteStatus;
}
private void ThreadSafeTxtBoxLutron(string message) { if (_lutronRichTextRxMessage.InvokeRequired) { var d = new ThreadSafeLutronCallback(ThreadSafeTxtBoxLutron); _lutronRichTextRxMessage.Invoke(d, new object[] { message }); } else { _lutronRichTextRxMessage.Text = message; } }
private void ThreadSafeTxtBoxElan(string message) { if (_elanRichTextRxMessage.InvokeRequired) { var d = new ThreadSafeElanCallback(ThreadSafeTxtBoxElan); _elanRichTextRxMessage.Invoke(d, new object[] { message }); } else { _elanRichTextRxMessage.Text = message; if (message.EndsWith("\r")) { MessageBoxEx.Show(message, "Message from Lutron Elan", 1000); } } }
private void ThreadSafeTxtBoxTuneSuite(string message) { if (_tuneSuiteRichTextRxMessage.InvokeRequired) { var d = new ThreadSafeTuneSuiteCallback(ThreadSafeTxtBoxTuneSuite); _tuneSuiteRichTextRxMessage.Invoke(d, new object[] { message }); } else { _tuneSuiteRichTextRxMessage.Text = message; if (message.EndsWith("\r")) { MessageBoxEx.Show(message, "Message from TuneSuite", 1000); } } }
private void _buttonConnectToLutron_Click(object sender, EventArgs e) { _lutronInterface.Connect(); }
private void _buttonDisconnectFromLutron_Click(object sender, EventArgs e) { _lutronInterface.Disconnect(); }
private void _buttonConnectToElan_Click(object sender, EventArgs e) { _elanInterface.Connect(); }
private void _buttonDisconnectFromElan_Click(object sender, EventArgs e) { _elanInterface.Disconnect(); }
private void _buttonConnectToTuneSuite_Click(object sender, EventArgs e) { _tuneSuiteInterface.Connect(); }
private void _buttonDisconnectFromTuneSuite_Click(object sender, EventArgs e) { _tuneSuiteInterface.Disconnect(); }
private void _buttonLutronSendMessage_Click(object sender, EventArgs e) { _lutronInterface.SendCommand(_lutronRichTextTxMessage.Text); }
private void _buttonElanSendMessage_Click(object sender, EventArgs e) { _elanInterface.SendCommand(_elanRichTextTxMessage.Text); }
private void _buttonTuneSuiteSendMessage_Click(object sender, EventArgs e) { _tuneSuiteInterface.SendCommand(_elanRichTextTxMessage.Text); }
private void _buttonLightOn_Click(object sender, EventArgs e) { _lutronInterface.SendCommand("sdl,14,100,0,S2"); }
private void _buttonLightOff_Click(object sender, EventArgs e) { _lutronInterface.SendCommand("sdl,14,0,0,S2"); }
private void _buttonStereoOnOff_Click(object sender, EventArgs e) { _elanInterface.SendCommand("sendir,4:3,1,40000,4,1,21,181,21,181,21,181,21,181,21,181,21,181,21,181,21,181,21,181,21,181,21,181,21,800"); }
private void _button30_Click(object sender, EventArgs e) { _tuneSuiteInterface.SendCommand("\xB8\x4D\xB5\x33\x30\x00\x30\x21\xB8"); }
private void _button31_Click(object sender, EventArgs e) { _tuneSuiteInterface.SendCommand("\xB8\x4D\xB5\x33\x31\x00\x30\x21\xB8"); }
private void _button26_Click(object sender, EventArgs e) { _tuneSuiteInterface.SendCommand("\xB8\x4D\xB5\x32\x36\x00\x30\x21\xB8"); }
}
}
和 GC_Interface 类：
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Windows.Forms;
namespace _GlobalCacheInterface
{
class GC_Interface
{
// Declare an event handler to notify when updates are available.
public event EventHandler<EventArgs> DataAvailable;
public string _returnString = "";
// Declare an event handler to notify status of connection.
public event EventHandler<EventArgs> Connected;
public bool _isConnected;
public AsyncCallback ReceiveCallback;
public Socket Client;
private string _ipAddress;
private int _port;
private bool _waitForEndCharacter;
private byte _endCharacter;
byte[] m_DataBuffer = new byte[10];
IAsyncResult m_Result;
public GC_Interface(string ipAddress, int port) { Init(ipAddress, port, false, 0); }
private void Init(string ipAddress, int port, bool waitForEndCharacter, byte endCharacter)
{
_ipAddress = ipAddress;
_port = port;
_waitForEndCharacter = waitForEndCharacter;
_endCharacter = endCharacter;
_isConnected = false;
}
public bool Connect()
{
try
{
// Create a TCP/IP socket.
Client = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
// Establish the remote endpoint for the socket.
var address = IPAddress.Parse(_ipAddress);
var remoteEP = new IPEndPoint(address, _port);
// Connect to the remote endpoint.
Client.Connect(remoteEP);
if (Client.Connected)
{
_isConnected = true;
ConnectedEventHandler();
WaitForData();
}
return true;
}
catch (SocketException se) { MessageBox.Show("\n connection failed, is the server running?\n" + se.Message ); return false; }
}
public bool SendCommand(string command)
{
try
{
// Convert the string data to byte data using ASCII encoding.
var byteData = Encoding.Default.GetBytes(command);
// Add a carraige-return to the end.
var newArray = new byte[byteData.Length + 1];
byteData.CopyTo(newArray, 0);
newArray[newArray.Length - 1] = 13;
if (Client == null) { return false; }
Client.Send(newArray);
return true;
}
catch (SocketException se) { MessageBox.Show(se.Message); return false; }
}
public void WaitForData()
{
try
{
if (ReceiveCallback == null) { ReceiveCallback = new AsyncCallback(OnDataReceived); }
var theSocPkt = new SocketPacket { thisSocket = Client };
m_Result = Client.BeginReceive(theSocPkt.DataBuffer, 0, theSocPkt.DataBuffer.Length, SocketFlags.None, ReceiveCallback, theSocPkt);
}
catch (SocketException se) { MessageBox.Show(se.Message); }
}
public class SocketPacket
{
public System.Net.Sockets.Socket thisSocket;
public byte[] DataBuffer = new byte[1];
}
public void OnDataReceived(IAsyncResult asyn)
{
try
{
SocketPacket theSockId = (SocketPacket)asyn.AsyncState;
var iRx = theSockId.thisSocket.EndReceive(asyn);
char[] Chars = new char[iRx + 1];
System.Text.Decoder d = System.Text.Encoding.UTF8.GetDecoder();
int CharLen = d.GetChars(theSockId.DataBuffer, 0, iRx, Chars, 0);
System.String szData = new System.String(Chars);
_returnString = _returnString + szData.Replace("\0", "");
// When an update is received, raise DataAvailable event
DataAvailableEventHandler();
WaitForData();
}
catch (ObjectDisposedException) { System.Diagnostics.Debugger.Log(0, "1", "\nOnDataReceived: Socket has been closed\n"); }
catch (SocketException se) { MessageBox.Show(se.Message); }
}
public bool Disconnect()
{
try
{
if (Client == null) { return false; }
Client.Close();
Client = null;
_isConnected = false;
return true;
}
catch (Exception) { return false; }
}
protected virtual void DataAvailableEventHandler()
{
var handler = DataAvailable;
if (handler != null) { handler(this, EventArgs.Empty); }
}
protected virtual void ConnectedEventHandler()
{
var handler = Connected;
if (handler != null) { handler(this, EventArgs.Empty); }
}
}
}