C# 如何检查TCP客户端连接是否已关闭?
我在玩弄TcpClient,试图弄清楚如何在连接断开时使Connected属性为false 我试过了C# 如何检查TCP客户端连接是否已关闭?,c#,sockets,tcpclient,networkstream,C#,Sockets,Tcpclient,Networkstream,我在玩弄TcpClient,试图弄清楚如何在连接断开时使Connected属性为false 我试过了 NetworkStream ns = client.GetStream(); ns.Write(new byte[1], 0, 0); 但它仍然不会显示TCP客户端是否已断开连接。您将如何使用TCP客户端进行此操作?据我所知/记得,除了读取或写入套接字之外,无法测试是否连接了套接字 我根本没有使用TcpClient,但是如果远程端正常关闭,Socket类将从Read调用返回0。 如果远程端没有
NetworkStream ns = client.GetStream();
ns.Write(new byte[1], 0, 0);
但它仍然不会显示TCP客户端是否已断开连接。您将如何使用TCP客户端进行此操作?据我所知/记得,除了读取或写入套接字之外,无法测试是否连接了套接字 我根本没有使用TcpClient,但是如果远程端正常关闭,Socket类将从Read调用返回0。 如果远程端没有正常关闭[我认为]会出现超时异常,无法记住类型抱歉
使用类似于“
if(socket.Connected){socket.Write(…)}”的代码创建竞争条件。您最好只调用套接字。编写并处理异常和/或断开连接。试试这个,它对我有用
private void timer1_Tick(object sender, EventArgs e)
{
if (client.Client.Poll(0, SelectMode.SelectRead))
{
if (!client.Connected) sConnected = false;
else
{
byte[] b = new byte[1];
try
{
if (client.Client.Receive(b, SocketFlags.Peek) == 0)
{
// Client disconnected
sConnected = false;
}
}
catch { sConnected = false; }
}
}
if (!sConnected)
{
//--Basically what you want to do afterwards
timer1.Stop();
client.Close();
ReConnect();
}
}
我使用定时器是因为我想定期检查连接状态
而且不在侦听代码的循环中[我觉得这会减慢发送-接收过程]我不建议您仅为测试套接字而尝试编写。也不要依赖.NET的连接属性
如果您想知道远程端点是否仍处于活动状态,可以使用TcpConnectionInformation:
TcpClient client = new TcpClient(host, port);
IPGlobalProperties ipProperties = IPGlobalProperties.GetIPGlobalProperties();
TcpConnectionInformation[] tcpConnections = ipProperties.GetActiveTcpConnections().Where(x => x.LocalEndPoint.Equals(client.Client.LocalEndPoint) && x.RemoteEndPoint.Equals(client.Client.RemoteEndPoint)).ToArray();
if (tcpConnections != null && tcpConnections.Length > 0)
{
TcpState stateOfConnection = tcpConnections.First().State;
if (stateOfConnection == TcpState.Established)
{
// Connection is OK
}
else
{
// No active tcp Connection to hostName:port
}
}
client.Close();
另请参见:
在MSDN上
在MSDN上
状态说明
netstaton
这里它是作为TcpClient上的一个扩展方法
public static TcpState GetState(this TcpClient tcpClient)
{
var foo = IPGlobalProperties.GetIPGlobalProperties()
.GetActiveTcpConnections()
.SingleOrDefault(x => x.LocalEndPoint.Equals(tcpClient.Client.LocalEndPoint));
return foo != null ? foo.State : TcpState.Unknown;
}
@uriel的答案对我来说非常有用,但我需要用C++/CLI编写它,这并不是一件小事。下面是(大致相当的)C++/CLI代码,其中添加了一些健壮性检查,以获得良好的度量
using namespace System::Net::Sockets;
using namespace System::Net::NetworkInformation;
TcpState GetTcpConnectionState(TcpClient ^ tcpClient)
{
TcpState tcpState = TcpState::Unknown;
if (tcpClient != nullptr)
{
// Get all active TCP connections
IPGlobalProperties ^ ipProperties = IPGlobalProperties::GetIPGlobalProperties();
array<TcpConnectionInformation^> ^ tcpConnections = ipProperties->GetActiveTcpConnections();
if ((tcpConnections != nullptr) && (tcpConnections->Length > 0))
{
// Get the end points of the TCP connection in question
EndPoint ^ localEndPoint = tcpClient->Client->LocalEndPoint;
EndPoint ^ remoteEndPoint = tcpClient->Client->RemoteEndPoint;
// Run through all active TCP connections to locate TCP connection in question
for (int i = 0; i < tcpConnections->Length; i++)
{
if ((tcpConnections[i]->LocalEndPoint->Equals(localEndPoint)) && (tcpConnections[i]->RemoteEndPoint->Equals(remoteEndPoint)))
{
// Found active TCP connection in question
tcpState = tcpConnections[i]->State;
break;
}
}
}
}
return tcpState;
}
bool TcpConnected(TcpClient ^ tcpClient)
{
bool bTcpConnected = false;
if (tcpClient != nullptr)
{
if (GetTcpConnectionState(tcpClient) == TcpState::Established)
{
bTcpConnected = true;
}
}
return bTcpConnected;
}
使用名称空间System::Net::Sockets;
使用名称空间System::Net::NetworkInformation;
TcpState GetTcpConnectionState(TCP客户端^TCP客户端)
{
TcpState TcpState=TcpState::未知;
if(tcpClient!=nullptr)
{
//获取所有活动的TCP连接
IPGlobalProperties ^ipProperties=IPGlobalProperties::GetIPGlobalProperties();
数组^tcpConnections=ipProperties->GetActiveTcpConnections();
如果((tcpConnections!=nullptr)&&(tcpConnections->Length>0))
{
//获取有问题的TCP连接的端点
端点^localEndPoint=tcpClient->Client->localEndPoint;
端点^remoteEndPoint=tcpClient->Client->remoteEndPoint;
//运行所有活动的TCP连接以查找有问题的TCP连接
对于(int i=0;iLength;i++)
{
if((tcpConnections[i]->LocalEndPoint->Equals(LocalEndPoint))&&(tcpConnections[i]->RemoteEndPoint->Equals(RemoteEndPoint)))
{
//发现有问题的活动TCP连接
tcpState=TCP连接[i]->状态;
打破
}
}
}
}
返回tcpState;
}
bool TCP已连接(TCP客户端^TCP客户端)
{
bool bTcpConnected=false;
if(tcpClient!=nullptr)
{
if(gettcpcConnectionState(tcpClient)=TcpState::已建立)
{
bTcpConnected=true;
}
}
返回bTcpConnected;
}
希望这会对某些人有所帮助。我已经创建了这个函数,并为我检查客户端是否仍然与服务器连接
/// <summary>
/// THIS FUNCTION WILL CHECK IF CLIENT IS STILL CONNECTED WITH SERVER.
/// </summary>
/// <returns>FALSE IF NOT CONNECTED ELSE TRUE</returns>
public bool isClientConnected()
{
IPGlobalProperties ipProperties = IPGlobalProperties.GetIPGlobalProperties();
TcpConnectionInformation[] tcpConnections = ipProperties.GetActiveTcpConnections();
foreach (TcpConnectionInformation c in tcpConnections)
{
TcpState stateOfConnection = c.State;
if (c.LocalEndPoint.Equals(ClientSocket.Client.LocalEndPoint) && c.RemoteEndPoint.Equals(ClientSocket.Client.RemoteEndPoint))
{
if (stateOfConnection == TcpState.Established)
{
return true;
}
else
{
return false;
}
}
}
return false;
}
//
///此函数将检查客户端是否仍与服务器连接。
///
///如果未连接,则为FALSE,否则为TRUE
公共bool isClientConnected()
{
IPGlobalProperties ipProperties=IPGlobalProperties.GetIPGlobalProperties();
TcpConnectionInformation[]tcpConnections=ipProperties.GetActiveTcpConnections();
foreach(TCP连接中的TCP连接信息c)
{
TcpState连接状态=c.状态;
if(c.LocalEndPoint.Equals(ClientSocket.Client.LocalEndPoint)和&c.RemoteEndPoint.Equals(ClientSocket.Client.RemoteEndPoint))
{
if(连接状态==TcpState.builded)
{
返回true;
}
其他的
{
返回false;
}
}
}
返回false;
}
在我的例子中,我向服务器发送了一些命令(在同一台计算机上的虚拟机中运行)并等待响应。但是,如果服务器在等待时意外停止,我不会收到任何通知。我尝试了其他海报提出的可能性,但都没有成功(总是说服务器仍然连接)。对我来说,唯一有效的方法是将0字节写入流:
var client = new TcpClient();
//... open the client
var stream = client.GetStream();
//... send something to the client
byte[] empty = { 0 };
//wait for response from server
while (client.Available == 0)
{
//throws a SocketException if the connection is closed by the server
stream.Write(empty, 0, 0);
Thread.Sleep(10);
}
彼得·沃恩和乌列尔的解决方案非常好。但是您还需要检查远程端点,因为您可以有多个到本地端点的开放连接
public static TcpState GetState(this TcpClient tcpClient)
{
var foo = IPGlobalProperties.GetIPGlobalProperties()
.GetActiveTcpConnections()
.SingleOrDefault(x => x.LocalEndPoint.Equals(tcpClient.Client.LocalEndPoint)
&& x.RemoteEndPoint.Equals(tcpClient.Client.RemoteEndPoint)
);
return foo != null ? foo.State : TcpState.Unknown;
}
到2019年,在跨平台异步环境中,我使用下面的代码继续检查TCP通道是否打开。例如,如果在我的Windows机器上拉了以太网电缆,或者在我的Android设备上禁用了Wifi,则会触发此检查
private async Task TestConnectionLoop()
{
byte[] buffer = new byte[1];
ArraySegment<byte> arraySegment = new ArraySegment<byte>(buffer, 0, 0);
SocketFlags flags = SocketFlags.None;
while (!_cancellationSource.Token.IsCancellationRequested)
{
try
{
await _soc.SendAsync(arraySegment, flags);
await Task.Delay(500);
}
catch (Exception e)
{
_cancellationSource.Cancel();
// Others can listen to the Cancellation Token or you
// can do other actions here
}
}
}
private异步任务TestConnectionLoop()
{
字节[]缓冲区=新字节[1];
ArraySegment ArraySegment=新的ArraySegment(缓冲区,0,0);
SocketFlags flags=SocketFlags.None;
while(!\u cancellationSource.Token.IsCancellationRequested)
{
尝试
{
wait _soc.SendAsync(arraySegment,flags);
等待任务。延迟(500);
}
捕获(例外e)
{
_cancellationSource.Cancel();
//其他人可以收听取消令牌或您
//您可以在这里执行其他操作
}
}
}
请注意,我发现System.Net.Sockets.TcpClient
的GSF.Communication
包装器非常有用,因为它有一个CurrentState
属性,指示套接字是打开/连接的还是关闭/断开的。您可以找到详细信息
GSF.Communication.TcpClient tcpClient;
void TestTcpConnectivity()
{
tcpClient = new GSF.Communication.TcpClient();
string myTCPServer = "localhost";
string myTCPport = "8080";
tcpClient.MaxConnectionAttempts = 5;
tcpClient.ConnectionAttempt += s_client_ConnectionAttempt;
tcpClient.ReceiveDataComplete += s_client_ReceiveDataComplete;
tcpClient.ConnectionException += s_client_ConnectionException;
tcpClient.ConnectionEstablished += s_client_ConnectionEstablished;
tcpClient.ConnectionTerminated += s_client_ConnectionTerminated;
tcpClient.ConnectionString = "Server=" + myTCPServer + ":" + myTCPport;
tcpClient.Initialize();
tcpClient.Connect();
Thread.Sleep(250);
if (tcpClient.CurrentState == ClientState.Connected)
{
Debug.WriteLine("Socket is connected");
// Do more stuff
}
else if (tcpClient.CurrentState == ClientState.Disconnected)
{
Debug.WriteLine(@"Socket didn't connect");
// Do other stuff or try again to connect
}
}
void s_client_ConnectionAttempt(object sender, EventArgs e)
{
Debug.WriteLine("Client is connecting to server.");
}
void s_client_ConnectionException(object sender, EventArgs e)
{
Debug.WriteLine("Client exception - {0}.", e.Argument.Message);
}
void s_client_ConnectionEstablished(object sender, EventArgs e)
{
Debug.WriteLine("Client connected to server.");
}
void s_client_ConnectionTerminated(object sender, EventArgs e)
{
Debug.WriteLine("Client disconnected from server.");
}
void s_client_ReceiveDataComplete(object sender, GSF.EventArgs<byte[], int> e)
{
Debug.WriteLine(string.Format("Received data - {0}.", tcpClient.TextEncoding.GetString(e.Argument1, 0, e.Argument2)));
}