TcpListener.Pending Method

Definition

Namespace:

System.Net.Sockets

Assemblies:

netstandard.dll, System.Net.Sockets.dll

Source:

TCPListener.cs

Determines if there are pending connection requests.

C#

public bool Pending();

Returns

Boolean

true if connections are pending; otherwise, false.

Exceptions

InvalidOperationException

The listener has not been started with a call to Start().

Examples

The following code example checks the Pending method. If a connection request is waiting to be accepted, then a call to the AcceptTcpClient method is made.

C#

const int portNumber = 13;

try
{
    // Use the Pending method to poll the underlying socket instance for client connection requests.
    IPAddress ipAddress = Dns.Resolve("localhost").AddressList[0];
    TcpListener tcpListener = new TcpListener(ipAddress, portNumber);
    tcpListener.Start();

    if (!tcpListener.Pending())
    {
        Console.WriteLine("Sorry, no connection requests have arrived");
    }
    else
    {
        //Accept the pending client connection and return a TcpClient object initialized for communication.
        TcpClient tcpClient = tcpListener.AcceptTcpClient();
        // Using the RemoteEndPoint property.
        Console.WriteLine("I am listening for connections on " +
            IPAddress.Parse(((IPEndPoint)tcpListener.LocalEndpoint).Address.ToString()) +
            "on port number " + ((IPEndPoint)tcpListener.LocalEndpoint).Port.ToString());

        //Close the tcpListener and tcpClient instances
        tcpClient.Close();
    }

    tcpListener.Stop();
}
catch (Exception e)
{
    Console.WriteLine(e.ToString());
}

Remarks

This non-blocking method determines if there are any pending connection requests. Because the AcceptSocket and AcceptTcpClient methods block execution until the Start method has queued an incoming connection request, the Pending method can be used to determine if connections are available before attempting to accept them.

Applies to

See also

• Start()
• AcceptSocket()
• AcceptTcpClient()