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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());
try {
    // Use the Pending method to poll the underlying socket instance for client connection requests.
    if (!tcpListener->Pending()) {
        Console::WriteLine(S"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(S"I am listening for connections on {0} on port number {1}", 
            IPAddress::Parse(__try_cast<IPEndPoint*>(tcpListener->LocalEndpoint)->Address->ToString()),
            __box(__try_cast<IPEndPoint*>(tcpListener->LocalEndpoint)->Port));

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

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

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0
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