Socket.Connected Property

Definition

Namespace:

System.Net.Sockets

Assembly:

System.Net.Sockets.dll

Source:

Socket.cs

Gets a value that indicates whether a Socket is connected to a remote host as of the last Send or Receive operation.

public:
 property bool Connected { bool get(); };

public bool Connected { get; }

member this.Connected : bool

Public ReadOnly Property Connected As Boolean

Property Value

Boolean

true if the Socket was connected to a remote resource as of the most recent operation; otherwise, false.

Examples

The following code example connects to a remote endpoint, checks the Connected property, and checks the current state of the connection.

client->Connect( anEndPoint );
if (  !client->Connected )
{
   Console::WriteLine( "Winsock error: {0}", Convert::ToString(
      System::Runtime::InteropServices::Marshal::GetLastWin32Error() ) );
}
   
// This is how you can determine whether a socket is still connected.
bool blockingState = client->Blocking;
try
{
   array<Byte>^tmp = gcnew array<Byte>(1);
   client->Blocking = false;
   client->Send( tmp, 0, static_cast<SocketFlags>(0) );
   Console::WriteLine( L"Connected!" );
}
catch ( SocketException^ e ) 
{
   // 10035 == WSAEWOULDBLOCK
   if ( e->NativeErrorCode.Equals( 10035 ) )
   {
      Console::WriteLine( "Connected from an exception!" );
   }
   else
   {
      Console::WriteLine( "Disconnected: {0}!", e->NativeErrorCode );
   }
}
finally
{
   client->Blocking = blockingState;
}

Console::WriteLine( "Connected: {0}", client->Connected );

// .Connect throws an exception if unsuccessful
client.Connect(anEndPoint);

// This is how you can determine whether a socket is still connected.
bool blockingState = client.Blocking;
try
{
    byte [] tmp = new byte[1];

    client.Blocking = false;
    client.Send(tmp, 0, 0);
    Console.WriteLine("Connected!");
}
catch (SocketException e)
{
    // 10035 == WSAEWOULDBLOCK
    if (e.NativeErrorCode.Equals(10035))
    {
        Console.WriteLine("Still Connected, but the Send would block");
    }
    else
    {
        Console.WriteLine("Disconnected: error code {0}!", e.NativeErrorCode);
    }
}
finally
{
    client.Blocking = blockingState;
}

Console.WriteLine("Connected: {0}", client.Connected);

    ' .Connect throws an exception if unsuccessful
    client.Connect(anEndPoint)
    
    ' This is how you can determine whether a socket is still connected.
    Dim blockingState As Boolean = client.Blocking
    Try
        Dim tmp(0) As Byte
        
        client.Blocking = False
        client.Send(tmp, 0, 0)
        Console.WriteLine("Connected!")
    Catch e As SocketException
        ' 10035 == WSAEWOULDBLOCK
        If e.NativeErrorCode.Equals(10035) Then
            Console.WriteLine("Still Connected, but the Send would block")
        Else
            Console.WriteLine("Disconnected: error code {0}!", e.NativeErrorCode)
        End If
    Finally
        client.Blocking = blockingState
    End Try
    
    Console.WriteLine("Connected: {0}", client.Connected)

End Sub

Remarks

The Connected property gets the connection state of the Socket as of the last I/O operation. When it returns false, the Socket was either never connected, or is no longer connected. Connected is not thread-safe; it may return true after an operation is aborted when the Socket is disconnected from another thread.

The value of the Connected property reflects the state of the connection as of the most recent operation. If you need to determine the current state of the connection, make a nonblocking, zero-byte Send call. If the call returns successfully or throws a WAEWOULDBLOCK error code (10035), then the socket is still connected; otherwise, the socket is no longer connected.

If you call Connect on a User Datagram Protocol (UDP) socket, the Connected property always returns true; however, this action does not change the inherent connectionless nature of UDP.