TcpState Enumeration

 

Specifies the states of a Transmission Control Protocol (TCP) connection.

Namespace:   System.Net.NetworkInformation
Assembly:  System (in System.dll)

public enum TcpState

Member nameDescription
Closed

The TCP connection is closed.

CloseWait

The local endpoint of the TCP connection is waiting for a connection termination request from the local user.

Closing

The local endpoint of the TCP connection is waiting for an acknowledgement of the connection termination request sent previously.

DeleteTcb

The transmission control buffer (TCB) for the TCP connection is being deleted.

Established

The TCP handshake is complete. The connection has been established and data can be sent.

FinWait1

The local endpoint of the TCP connection is waiting for a connection termination request from the remote endpoint or for an acknowledgement of the connection termination request sent previously.

FinWait2

The local endpoint of the TCP connection is waiting for a connection termination request from the remote endpoint.

LastAck

The local endpoint of the TCP connection is waiting for the final acknowledgement of the connection termination request sent previously.

Listen

The local endpoint of the TCP connection is listening for a connection request from any remote endpoint.

SynReceived

The local endpoint of the TCP connection has sent and received a connection request and is waiting for an acknowledgment.

SynSent

The local endpoint of the TCP connection has sent the remote endpoint a segment header with the synchronize (SYN) control bit set and is waiting for a matching connection request.

TimeWait

The local endpoint of the TCP connection is waiting for enough time to pass to ensure that the remote endpoint received the acknowledgement of its connection termination request.

Unknown

The TCP connection state is unknown.

This enumeration defines valid values for the State property. TCP is a transport layer protocol responsible for reliably sending and receiving data packets. The TCP states in this enumeration are defined in IETF RFC 793 available at http://www.ietf.org.

The following code example counts the established TCP connections.

public static void CountTcpConnections()
{
    IPGlobalProperties properties = IPGlobalProperties.GetIPGlobalProperties();
    TcpConnectionInformation[] connections = properties.GetActiveTcpConnections();
    int establishedConnections = 0;

    foreach (TcpConnectionInformation t in connections)
    {
        if (t.State == TcpState.Established)
        {
             establishedConnections++;
        }
        Console.Write("Local endpoint: {0} ",t.LocalEndPoint.Address);
        Console.WriteLine("Remote endpoint: {0} ",t.RemoteEndPoint.Address);

    }
     Console.WriteLine("There are {0} established TCP connections.",
        establishedConnections);
}

.NET Framework
Available since 2.0
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