SubstrateVM: MulticastSocket.joinGroup() fails

[belaban]

[belaban]

I'm trying to get JGroups running with IP multicast support, but the showstopper is MulticastSocket.joinGroup():

Exception in thread "main" java.lang.UnsatisfiedLinkError: java.net.PlainDatagramSocketImpl.join(Ljava/net/InetAddress;Ljava/net/NetworkInterface;)V [symbol: Java_java_net_PlainDatagramSocketImpl_join or Java_java_net_PlainDatagramSocketImpl_join__Ljava_net_InetAddress_2Ljava_net_NetworkInterface_2]
	at com.oracle.svm.jni.access.JNINativeLinkage.getOrFindEntryPoint(JNINativeLinkage.java:145)
	at com.oracle.svm.jni.JNIGeneratedMethodSupport.nativeCallAddress(JNIGeneratedMethodSupport.java:57)
	at java.net.PlainDatagramSocketImpl.join(PlainDatagramSocketImpl.java)
	at java.net.AbstractPlainDatagramSocketImpl.join(AbstractPlainDatagramSocketImpl.java:178)
	at java.net.MulticastSocket.joinGroup(MulticastSocket.java:323)
	at org.jgroups.tests.MulticastTest.testMulticastSocket(MulticastTest.java:41)
	at org.jgroups.tests.MulticastTest.main(MulticastTest.java:34)

The issue is also present in DatagramChannel.join().

To reproduce:

• Use native-compile on MulticastTest [1]
• Run with MulticastSocket: ./org.jgroups.tests.multicasttest
• Run with DatagramChannel: ./org.jgroups.tests.multicasttest -nio

The latter issue seems to be related to [3].

[1] https://github.com/belaban/JGroups/blob/master/tests/other/org/jgroups/tests/MulticastTest.java
[2] https://issues.jboss.org/browse/JGRP-2344
[3] #474

[dmlloyd]

I've been looking at this. I think I can probably produce an initial PR sometime in the next few days.

[belaban]

Thanks a bunch, David! The beers next time we meet are on me! :-)

[dmlloyd]

I've opened pull request #1404. This fixes the old I/O case, but not the NIO case yet.

[belaban]

Thanks, David!
This fixes the showstopper that's preventing UDP from running! The NIO case is not currently a showstopper for me.

[dmlloyd]

That's what I figured. NIO is a bit tricky because it's very different between Java 8 and Java 11, and I'm not sure it's worth investing a large effort to get Java 8 going. We'll see what they say about the initial PR before I try to cross that bridge.