Ping Class - Assinchronous ping

T

teixeira

Regular
Joined
Apr 5, 2005
Messages
94
Location
LEIRIA-PORTUGAL
Hi All,

I wanna make a class to check when my printer is connected or disconnected from the network.
This is for prevent user to send a job without the printer beeing online, and with this i wanna show some alarms.
This is using a normal socket connection, and i'm pinging the printer when i start the program and when i'm ready to send a job to it.
I use the ping class and after the event has been 'PingCompleted' raisen, i wanna make some actions, until here all well, but as the ping request is sent
assincronously i having some problems, because i wanna wait for ping status before i go ahead, see my code:

Code: 
       /// <summary>
        /// Pinga a Impressora com 32Bytes de lixo e espera o echo da mensagem para verificar se está ou n ligada
        /// </summary>
        /// <param name="ip">Ip da Impressora</param>
        public static void CheckIfPrinterAlive(string ip)
        {
            //Notifica a thread que um determinado evento ocorreu
            AutoResetEvent waiter = new AutoResetEvent(false);

            //Cria uma instancia de ping
            Ping pingSender = new Ping();

            // When the PingCompleted event is raised,
            // the PingCompletedCallback method is called.
            pingSender.PingCompleted += new PingCompletedEventHandler(PingCompletedCallback);

            // Create a buffer of 32 bytes of data to be transmitted.
            string data = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
            byte[] buffer = Encoding.ASCII.GetBytes(data);

            // Wait 12 seconds for a reply.
            int timeout = 12000;

            // Set options for transmission:
            // The data can go through 64 gateways or routers
            // before it is destroyed, and the data packet
            // cannot be fragmented.
            PingOptions options = new PingOptions(64, true);

            // Send the ping asynchronously.
            // Use the waiter as the user token.
            // When the callback completes, it can wake up this thread.
            pingSender.SendAsync(ip, timeout, buffer, options, waiter);
			
			
			//Here the code should stop until i get the ping reply
			//How can i wait here until the assinchronous ping request has completed?
        }

        private static void PingCompletedCallback(object sender, PingCompletedEventArgs e)
        {
            PingReply reply = e.Reply;

            if (reply.Status == IPStatus.Success)
            {
				printerAlive = true;
            }
            else
            {
				printerAlive = false;
            }
            // Let the main thread resume.
            ((AutoResetEvent)e.UserState).Set();
        }

TIA

Tiago Teixeira
 
The whole point of the SendAsync method is that it sends asynchronously and doesn't wait. If you need to wait just use the Send method instead.

Alternatively as you are handling the call via a callback why do you need to wait?
 
maybe you're right send just goes fine.
as i took this example from msft msdn help i make some confusion my self.
ill try like that

Thanks

Tiago Teixeira
 
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