Problem with JoinMulticastGroup and DFÜ Modem connection

[Frank an der Heiden]

Hi folks,

I have a problem with the following example:

################################################## ####

My Receiver Class
*****************
class UdpReceiver
{
public static void Main()
{
UdpClient client = new UdpClient(10500);
client.JoinMulticastGroup(IPAddress.Parse("224.100 .0.1"));
Console.WriteLine("Waiting.....");
IPEndPoint iep = new IPEndPoint(IPAddress.Any, 0);
byte[] data = client.Receive(ref iep);
string stringData = Encoding.ASCII.GetString(data, 0,data.Length);
Console.WriteLine("received: {0}", stringData);
client.Close();
}
}

My Sender Class
******************
class UdpSender
{
public static void Main()
{
UdpClient sender = new UdpClient();
IPEndPoint iep = new
IPEndPoint(IPAddress.Parse("224.100.0.1"),10500);
byte[] data = Encoding.ASCII.GetBytes("This is a test message");
sender.Send(data, data.Length, iep);
sender.Close();
}
}

##################################################

Generally everything works fine, when sending messages from my sender
to the receiver until I have only a connection in my LAN.
When additionally connecting the server to the Internet by modem (DFÜ),
then the sender receives NO message any longer.

I really tried many diferent combinations of ip-Adresses and ports etc,
"played" with my network-settings of my LAN and DFÜ, but nothing works.

It seems that the messages of the sender are routed in the internet, but how
can
I avoid this?

I found many examples how to establish an UDP-connection between
client and server and all work .... UNTIL my modem comes up!!

It's really frustrating, because meanwhile I have no more ideas what I could
try to fix this.

Any help or hint is more than welcome

Thanx in advance

Frank

[Rich Blum]

[e-mail] (Frank an der Heiden) wrote in message news:<22**************************@posting.google. com>...

I have a problem with the following example:

My Sender Class
******************
class UdpSender
{
public static void Main()
{
UdpClient sender = new UdpClient();
IPEndPoint iep = new
IPEndPoint(IPAddress.Parse("224.100.0.1"),10500);
byte[] data = Encoding.ASCII.GetBytes("This is a test message");
sender.Send(data, data.Length, iep);
sender.Close();
}
}

##################################################

Generally everything works fine, when sending messages from my sender
to the receiver until I have only a connection in my LAN.
When additionally connecting the server to the Internet by modem (DFÜ),
then the sender receives NO message any longer.

I really tried many diferent combinations of ip-Adresses and ports etc,
"played" with my network-settings of my LAN and DFÜ, but nothing works.

It seems that the messages of the sender are routed in the internet, but how
can
I avoid this?

Frank -

When you use the default UdpClient() constructor for your sender,
it will "assign the most appropriate local IP address and port number"
by default for the outgoing packets. Unfortunately for you what it
thinks is most appropriate is not what you think is most appropriate.

To avoid this you need to specify the IP address of your LAN
connection along with a default port number as an IPEndPoint object
within your UdpClient constructor:

IPEndPoint iep = new IPEndPoint(IPAddress.Parse("localLANIP"),
9050);
UdpClient sender = new UdpClient(iep);
....

This should force the UdpClient object to bind to the LAN
interface for your multicast messages instead of the modem interface.
Hope this helps solve your problem.

Rich Blum - Author
"C# Network Programming" (Sybex)
http://www.sybex.com/sybexbooks.nsf/Booklist/4176
"Network Performance Open Source Toolkit" (Wiley)
http://www.wiley.com/WileyCDA/WileyT...471433012.html

[Frank an der Heiden]

> >

Frank -

When you use the default UdpClient() constructor for your sender,
it will "assign the most appropriate local IP address and port number"
by default for the outgoing packets. Unfortunately for you what it
thinks is most appropriate is not what you think is most appropriate.

To avoid this you need to specify the IP address of your LAN
connection along with a default port number as an IPEndPoint object
within your UdpClient constructor:

IPEndPoint iep = new IPEndPoint(IPAddress.Parse("localLANIP"),
9050);
UdpClient sender = new UdpClient(iep);
....

This should force the UdpClient object to bind to the LAN
interface for your multicast messages instead of the modem interface.
Hope this helps solve your problem.

Rich Blum - Author
"C# Network Programming" (Sybex)
http://www.sybex.com/sybexbooks.nsf/Booklist/4176
"Network Performance Open Source Toolkit" (Wiley)
http://www.wiley.com/WileyCDA/WileyT...471433012.html

Yipiiiihhhh,

Now it works fine!
It was not so easy to obtain my specific Broadcast-Address for
the sender, because the software should run in different networks,
but also this works now!!

Thank You for your prompt reply, Rich!

Good Night
Frank