C#如何防止插座或连接关闭?
我正在使用C#编写的应用程序,通过IP连接到我们的一些设备。应用程序与设备连接良好,我们可以发送配置所需的命令。我遇到的问题是,在断开连接后,在大约40秒到一分钟内没有发送任何命令。我想知道我能做些什么使插座保持至少几分钟的活动状态。需要一些关于实施心跳的指导,任何帮助都将不胜感激 下面是我们正在使用的代码C#如何防止插座或连接关闭?,c#,C#,我正在使用C#编写的应用程序,通过IP连接到我们的一些设备。应用程序与设备连接良好,我们可以发送配置所需的命令。我遇到的问题是,在断开连接后,在大约40秒到一分钟内没有发送任何命令。我想知道我能做些什么使插座保持至少几分钟的活动状态。需要一些关于实施心跳的指导,任何帮助都将不胜感激 下面是我们正在使用的代码 using System; using System.Net; using System.Net.Sockets; using System.Threading; u
using System;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Text;
using System.Globalization;
// State object for receiving data from remote device.
public 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();
}
public class AsynchronousClient
{
// The port number for the remote device.
//private const int port = 1000;
// ManualResetEvent instances signal completion.
private static ManualResetEvent connectDone =
new ManualResetEvent(false);
private static ManualResetEvent sendDone =
new ManualResetEvent(false);
private static ManualResetEvent receiveDone =
new ManualResetEvent(false);
// The response from the remote device.
private static String response = String.Empty;
static Socket client;
internal static Boolean StartClient(string ip_address, int port)
{
// Connect to a remote device.
Boolean bRtnValue = false;
try
{
// Establish the remote endpoint for the socket.
// The name of the
// remote device is "host.contoso.com".
//IPHostEntry ipHostInfo = Dns.Resolve("host.contoso.com");
IPAddress ipAddress = IPAddress.Parse(ip_address);
IPEndPoint remoteEP = new IPEndPoint(ipAddress, port);
// Create a TCP/IP socket.
client = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
// Connect to the remote endpoint.
client.BeginConnect(remoteEP,
new AsyncCallback(ConnectCallback), client);
connectDone.WaitOne();
// Send test data to the remote device.
string msg = ((char)2) + "S" + (char)13;
Send(client, msg);
//sendDone.WaitOne();
// Receive the response from the remote device.
Receive(client);
//receiveDone.WaitOne();
// Write the response to the console.
Console.WriteLine("Response received : {0}", response);
bRtnValue = true;
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
//return value
return bRtnValue;
}
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, 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.Clear();
state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead));
Console.WriteLine(DateTime.Now.ToLongTimeString() + ": " + state.sb.ToString());
//54A111503000000000017D8857E3
//IDSSSSSSSSSSSSSSSSTTTTCCCCKK 017D
if (state.sb.ToString(0, 2) == "54")
{
string hexString = state.sb.ToString(18, 4);
int num = Int32.Parse(hexString, NumberStyles.HexNumber);
double degreesF = ((double)num / 16.0) * 9.0 / 5.0 + 32.0;
string f = degreesF.ToString("#.#");
Console.WriteLine(" " + f);
}
// Get the rest of the data.
client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(ReceiveCallback), state);
}
else
{
Console.WriteLine("data");
// 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());
}
}
private static void Send(Socket client, String data)
{
// Convert the string data to byte data using ASCII encoding.
byte[] byteData = Encoding.ASCII.GetBytes(data);
// Begin sending the data to the remote device.
client.BeginSend(byteData, 0, byteData.Length, 0,
new AsyncCallback(SendCallback), client);
}
private static void SendCallback(IAsyncResult ar)
{
try
{
// Retrieve the socket from the state object.
Socket client = (Socket)ar.AsyncState;
// Complete sending the data to the remote device.
int bytesSent = client.EndSend(ar);
Console.WriteLine("Sent {0} bytes to server.", bytesSent);
// Signal that all bytes have been sent.
sendDone.Set();
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
internal void StartListening(string ip_address, int port)
{
StartClient(ip_address, port);
}
其原因是所谓的超时,据我所知,当连接的另一端中止、断开连接或以其他方式完全停止传输数据时,每个网络协议都要处理的一个重要特性。毕竟,没有办法发送一个数据包,上面写着“我的猫刚刚把我的路由器撞坏了,中断了连接。”
您需要做的是,如评论中所述,通过网络定期发送no op(即不执行任何操作)命令,以防止超时。这类数据包被称为“心跳”或“保持激活”信号,发送频率应远高于实际超时,以防丢失或延迟到达。这最好通过启动一个辅助线程来实现,该线程在连接标记为打开时只发送心跳。您需要实现一个计时器,在没有数据要发送时模拟心跳,即在发送最后一个数据包后,启动一个计时器几秒钟。如果在取消之前有数据要发送,请发送数据并重新启动计时器。如果计时器超时,您将发送一个虚拟数据包,并在相同的超时时间后重新启动计时器。如果设备支持,您不能定期发送任何类似ping(无操作)的命令以保持连接吗?或者,查看套接字保持活动选项。在任何情况下,这都不包括连接重置或网络关闭的情况,此时您必须重新连接。代码??????听起来您连接的服务器正在断开连接。。。在不了解其行为规则的情况下,很难告诉您任何事情,但是如果它在一定的空闲时间后断开连接,则会发送Ping消息……仅供参考:像这样的工具值得学习。它可以非常方便地确定谁决定终止连接,等等。