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TcpListener.Pending Method

Determines if there are pending connection requests.

Namespace:  System.Net.Sockets
Assembly:  System (in System.dll)
public bool Pending()

Return Value

Type: System.Boolean
true if connections are pending; otherwise, false.
ExceptionCondition
InvalidOperationException

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

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.

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.


      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());

.NET Framework

Supported in: 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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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