Re: UDP applet

Knute Johnson <>
Wed, 18 Apr 2007 09:45:44 -0700
<ZWrVh.530981$Ju2.437435@newsfe16.lga> wrote:

thanks you seemed to have prooved that a regular applet can receive
udp datagram from its server though all that remains mysterious and my
server does not work:

- There is a firewall on my server side and the windows xp firewall
here on my desktop
- your udp applet works fine
from my desktop
- your udp applet does not work with my c# echo udp (I plugged it to
my server)- server receives packets and echo them back but they nerver
reach back the applet
-my c# echo udp works fine with a standalone java app from my local
-my applet (which does pretty much the same than knute's one) does not
work with my c# echo udp server - - server receive packets and echo
them back but they nerver reach back the applet
- if my applet is signed then it works fine with my c# echo udp server

I need this applet working without being signed !!
Any clue ??

here is new version of my c# echo udp server :

   protected void StartUDP()
        Socket soUDP = new Socket(AddressFamily.InterNetwork,
               SocketType.Dgram, ProtocolType.Udp);

            //60 sec timeout
SocketOptionName.ReceiveTimeout, 3000);

            // On doit lier la Socket ? un port d'?coute sur la
machine. On choisit ?galement de se mettre en ?coute sur toutes les
interfaces r?seaux pr?sentes (IPAddress.Any).
            soUDP.Bind(new IPEndPoint(IPAddress.Any,
            Application["log"] = Application["log"] + "isBinded<br>";
            Application["isStarted"] = true;
            Application["serverStatus"] = "UDP server isStarted at " +
DateTime.Now + "<br>";
            Application["log"] = Application["log"] + "start waiting
at " + DateTime.Now + "<br>";

            while (!((Boolean)(Application["stopRequested"])))
                //if datagram receveided is bigger than 12 exception
will be thrown on receive
                Byte[] received = new Byte[12];

                // Empty endpoint
                EndPoint remoteEP = new IPEndPoint(IPAddress.Any, 0);

                    //remoteEP will be instanciated by the method
                    // with remote sender info
                    int bytesReceived = soUDP.ReceiveFrom(received,
ref remoteEP);
                    //echoes back
                    soUDP.SendTo(received, remoteEP);

                    String dataReceived =
                    IPEndPoint ip = (IPEndPoint)remoteEP;
                    Application["log"] = Application["log"] +
"Datagram packet received from "+ ip.Address +":"+ip.Port+ "<br>";
                    Application["log"] = Application["log"] +
"Datagram packet length=" + bytesReceived + " dataReceived=" +
dataReceived + "<br>";
                    Application["log"] = Application["log"] + "Echoed
it back to " + ip.Address +":"+ip.Port+ "<br>";

                catch (Exception t)
                    // Here it is a timeout (but not a
                   // Application["log"] = Application["log"] + "" +

        catch (Exception e)
            Application["serverStatus"] = "UDP server probably stoped
on exception at " + DateTime.Now + "<br>";
            Application["isStarted"] = false;
            Application["log"] = Application["log"] + "Exception at "
+ DateTime.Now + "<br>";
            Application["log"] = Application["log"] + e.Message +

            Application["isStarted"] = false;
            Application["log"] = Application["log"] + "finally closing
            Application["serverStatus"] = "UDP server stoped at " +
DateTime.Now + "<br>";


Let's see the complete code of your applet.


Knute Johnson
email s/nospam/knute/

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