sockets - Java Soket cannot send multicast packet on Raspberry Pi -


i try run code in raspberry pi. socket can receive data multicast group, however, shows following error when tries send data:

pi@raspberrypi:~ $ java  protocol java.net.multicastsocket@647e05 java.io.ioexception: cannot assign requested address     @ java.net.plaindatagramsocketimpl.send(native method)     @ java.net.datagramsocket.send(datagramsocket.java:693)     @ protocol.getsensordata(protocol.java:201)     @ protocol.main(protocol.java:305)

here code:

import java.net.*; import java.util.*;  public class protocol {      private multicastsocket socket = null;     private multicastsocket socket_switchpanel = null;     string multicast_address = "";     int port = -1;      public protocol(string nic, boolean isbyip, string multcastaddress, int port) {         this.multicast_address = multcastaddress;         this.port = port;         try {             inetaddress dstaddr = inetaddress.getbyname(multicast_address);             socket = new multicastsocket(port);             inetsocketaddress socketaddress = new inetsocketaddress(multicast_address, port);              networkinterface ni = networkinterface.getbyname(nic);             socket.setreuseaddress(true);             socket.joingroup(socketaddress, ni);             system.out.println(ni);          } catch (exception e) {             system.out.println(e);             e.printstacktrace();             if (socket != null) {                 socket.close();             }         }     }      public void close_socket() {         if (socket != null) {             socket.close();         }     }      public integer getsensordata() {          byte[] msg = new byte[]{                 (byte) 0xab, 0x04, (byte) 0x82, (byte) 0xcd, 0x00, (byte) 0x01};         try {             // ip address             inetaddress dstaddr = inetaddress.getbyname(multicast_address);              final datagrampacket out = new datagrampacket(msg, msg.length, dstaddr, port);             socket.send(out);             // receive data until timeout or stop prematurely on users' request             try {                 // process multi cast response(s)                 final byte[] inputbuffer = new byte[30];                 final datagrampacket in = new datagrampacket(inputbuffer, inputbuffer.length);                 socket.setsotimeout(500);                 socket.receive(in);                 byte[] data = in.getdata();                 return 1;              } catch (exception ste) {             }         } catch (exception e) {             e.printstacktrace();         }         return 1;     }       public static void main(string[] args) { //        tring nic, boolean isbyip, string multcastaddress, int port         protocol dc = new protocol("wlan0",                 false,                 "ff12:00:00:00:4479:00:00:00",                 50000);         int ab = dc.getsensordata();         system.out.println(ab);         return;     } }

your java may picking ip v4 instead of ip v6 (like multicast address seems point to). try starting

-djava.net.preferipv6addresses=true

usually happens java preferring v6 on v4, might have special case here. alternatively, you're using invalid multicast address (looking @ https://www.iana.org/assignments/ipv6-multicast-addresses/ipv6-multicast-addresses.xhtml#ipv6-scope doesn't appear addresses starting ff12 valid ipv6 multicast addresses).


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