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Socket.Connected Property

.NET Framework 4

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

Namespace:  System.Net.Sockets
Assembly:  System (in System.dll)
C#
C++
F#
VB
Copy 
public bool Connected { get; }

Property Value

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

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.

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.

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

C#
C++
VB
Copy 

// .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);

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
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Example does not work
I am in agreement with the last poster.  The example code as it *does not work*.  A zero length packet transmission does not result in the Connected state being updated.
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Example does not work
I have test the example method but it doesn't work.
In my case I  have a TCP Client and a TCP Server.
If i shutdown the TCP SERVER (closing the application while the client is still connected) that piece of code still returns TRUE as my client is still Connected.
Why?
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