NPE if binding JGroups to an IP without interface ------------------------------------------------- Key: JGRP-2527 URL: https://issues.redhat.com/browse/JGRP-2527 Project: JGroups Issue Type: Bug Affects Versions: 4.2.9 Reporter: Pedro Ruivo Assignee: Bela Ban Priority: Minor Fix For: 4.2.12, 5.1.5 If you bind JGroups to 127.0.2.1 (or any IP without an interface, like 127.0.0.0/8 - loopback IP addresses (refers to self) RFC 5735), JGroups fails with an NPE: {noformat} Caused by: java.lang.NullPointerException at org.jgroups.protocols.UDP.dumpSocketInfo(UDP.java:558) at org.jgroups.protocols.UDP.createSockets(UDP.java:422) at org.jgroups.protocols.UDP.start(UDP.java:292) at org.jgroups.stack.ProtocolStack.startStack(ProtocolStack.java:868) at org.jgroups.JChannel.startStack(JChannel.java:980) at org.jgroups.JChannel._preConnect(JChannel.java:844) at org.jgroups.JChannel.connect(JChannel.java:349) at org.jgroups.JChannel.connect(JChannel.java:343) {noformat} The exception comes from this line: [https://github.com/belaban/JGroups/blob/4.x/src/org/jgroups/protocols/UDP...] {{NetworkInterface.getByInetAddress(bind_addr)}} returns {{null}} since the IP does not have an interface. It would be nice to have a null check here to prevent the NPE. This is useful for local testing when `port_range=0`. It allows having a dedicated IP for each JGroups instance. Workaround: The workaround requires you to create a virtual interface {noformat} sudo ifconfig lo:0 127.0.2.1 up {noformat}