我正在尝试使用TcpClient,并试图找出如何在连接断开时使Connected属性显示为false。
我尝试过:
NetworkStream ns = client.GetStream();
ns.Write(new byte[1], 0, 0);
但是它仍然无法显示TcpClient是否已断开连接。如何使用TcpClient解决这个问题?
我正在尝试使用TcpClient,并试图找出如何在连接断开时使Connected属性显示为false。
我尝试过:
NetworkStream ns = client.GetStream();
ns.Write(new byte[1], 0, 0);
但是它仍然无法显示TcpClient是否已断开连接。如何使用TcpClient解决这个问题?
我不建议你为了测试socket而进行尝试写操作。也不要依赖于.NET的Connected属性。
如果你想知道远程终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();
相关链接:
MSDN上的TcpConnectionInformation
MSDN上的IPGlobalProperties
TcpState状态说明
Wikipedia上的Netstat
这是在TcpClient上的扩展方法。
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;
}
Peter Wone和uriel的解决方案非常好。但您还需要检查远程终点,因为您可以在本地终点上拥有多个打开的连接。
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;
}
我创建了这个函数并且它可以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;
}
@uriel的答案对我非常有帮助,但我需要用C++/CLI编写它,这并不是完全容易的。这是(大致等效的)C++/CLI代码,并为了保险起见添加了一些鲁棒性检查。
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;
}
希望这能对某些人有所帮助。
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();
IPEndPoint.Equals()
来搜索检索到的TCP连接列表,以查找与所使用的TCP客户端TcpClient.Client
的端点相同的连接。// Creation of TCP client:
m_tcpClient = new TcpClient ();
m_tcpClient.Connect ("100.111.1.251", 54321);
// Query of the local and remote IP endpoints in Visual Studio Immediate Window:
?m_tcpClient.Client.LocalEndPoint
{[::ffff:100.111.1.254]:55412}
Address: {::ffff:100.111.1.254}
AddressFamily: InterNetworkV6
Port: 55412
?m_tcpClient.Client.RemoteEndPoint
{[::ffff:100.111.1.251]:54321}
Address: {::ffff:100.111.1.251}
AddressFamily: InterNetworkV6
Port: 54321
// Query of the addresses of the local and remote IP endpoints in Visual Studio Immediate Window:
?((IPEndPoint)m_tcpClient.Client.LocalEndPoint).Address
{::ffff:100.111.1.254}
Address: '((IPEndPoint)m_tcpClient.Client.LocalEndPoint).Address.Address' threw an exception of type 'System.Net.Sockets.SocketException'
AddressFamily: InterNetworkV6
IsIPv4MappedToIPv6: true
IsIPv6LinkLocal: false
IsIPv6Multicast: false
IsIPv6SiteLocal: false
IsIPv6Teredo: false
ScopeId: 0
?((IPEndPoint)m_tcpClient.Client.RemoteEndPoint).Address
{::ffff:100.111.1.251}
Address: '((IPEndPoint)m_tcpClient.Client.RemoteEndPoint).Address.Address' threw an exception of type 'System.Net.Sockets.SocketException'
AddressFamily: InterNetworkV6
IsIPv4MappedToIPv6: true
IsIPv6LinkLocal: false
IsIPv6Multicast: false
IsIPv6SiteLocal: false
IsIPv6Teredo: false
ScopeId: 0
IPGlobalProperties.GetActiveTcpConnections()
看起来总是返回带有IPv4地址的 IPEndPoint
对象:?IPGlobalProperties.GetIPGlobalProperties().GetActiveTcpConnections()[48].LocalEndPoint
{100.111.1.254:55412}
Address: {100.111.1.254}
AddressFamily: InterNetwork
Port: 55412
EndPoint
对象引用相同的IP端点,IPEndPoint.Equals()
可能返回false。Equals()
方法,例如:public static class EndPointHelper
{
private static readonly AddressFamily[] addressFamilies =
{
AddressFamily.InterNetwork,
AddressFamily.InterNetworkV6
};
public static bool Equals (EndPoint? endPoint1, EndPoint? endPoint2)
{
if (endPoint1 is IPEndPoint ipEndPoint1 &&
endPoint2 is IPEndPoint ipEndPoint2)
{
if (ipEndPoint1.AddressFamily != ipEndPoint2.AddressFamily &&
addressFamilies.Contains(ipEndPoint1.AddressFamily) &&
addressFamilies.Contains(ipEndPoint2.AddressFamily))
{
var ipAddress1AsV6 = ipEndPoint1.Address.MapToIPv6();
var ipAddress2AsV6 = ipEndPoint2.Address.MapToIPv6();
return ipAddress1AsV6.Equals(ipAddress2AsV6)
&& ipEndPoint1.Port.Equals(ipEndPoint2.Port);
}
}
return object.Equals (i_endPoint1, i_endPoint2);
}
}
IPGlobalProperties.GetActiveTcpConnections()
存在内存泄漏问题(请参见https://github.com/dotnet/runtime/issues/64735),这个问题在 .NET 5中将不再修复,因为已经停止支持。这个错误在 .NET 6中不存在。如果你被限制在使用 .NET 5,则必须通过在本地变量中记住连接状态来解决它(例如,使用 EnumState m_cachedState)。在每个相关操作之后设置此变量,例如,在 Connect()
之后,您必须将其设置为 EnumState.Connected
。var socket = m_tcpClient.Client;
bool state = socket.Poll (100, SelectMode.SelectRead);
int available = socket.Available;
return state && available == 0 // Condition for externally closed connection. The external close will not be recognized until all received data has been read.
? EnumState.Idle
: m_cachedState;
GSF.Communication
包装器对于 System.Net.Sockets.TcpClient
很有帮助,因为它具有 CurrentState
属性,指示套接字是打开/连接还是关闭/断开连接。您可以在此处找到有关 NuGet 包的详细信息:
https://github.com/GridProtectionAlliance/gsf
以下是如何设置一个简单的TCP套接字并测试其连接是否成功:
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)));
}
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
}
}
}
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);
}
试试这个,对我有效
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();
}
}
我使用了计时器,因为我想要在固定的时间间隔内检查连接状态,而不是在循环中使用监听代码[我感觉这会减缓发送-接收过程]
FirstOrDefault
替代SingleOrDefault
。 - mozkomor05.SingleOrDefault(x => x.LocalEndPoint.Equals(tcpClient.Client.LocalEndPoint) && x.RemoteEndPoint.Equals(tcpClient.Client.RemoteEndPoint));
- Wagner PereiraIPEndPoint.Equals()
可能会失败!连接将使用“IPv4映射的IPv6地址”,套接字的两个IP端点在TcpClient.Client
中将分别为InterNetworkV6
(IPv6),但从GetActiveTcpConnections()
检索到的端点将为InterNetwork
(IPv4)。//我无法在此处添加屏幕截图,因此我已经添加了一个答案:https://dev59.com/xHM_5IYBdhLWcg3waSb9#72701813 - Tobias Knauss