Multicastsocket , Why can't I new a instance of Multicastsocket ?

Dear Sir:

I want to create a multicast socket, and do the following:

MulticastSocket s;

try

{

s= new Multicastsocket(6789); //create line

}

catch(IOException e)

{

return;

}

but this program can't create the Socket correctly, and always trace into

Java SDK

" public StringBuffer()

{

this(16);

}

"

Who can give me some advice?

what is your multicast IP address? where is the code for your instance joining the multicast group?