Fix #242

When processing events, AttachCurrentThread is called, but matching
DetachCurrentThread was not being called

This prevented main thread from exiting

src/Events.cpp

@@ -197,6 +197,8 @@ void Events::sendToUser(zts_event_msg_t* msg)
             id = msg->peer ? msg->peer->peer_id : 0;
         }
         env->CallVoidMethod(javaCbObjRef, javaCbMethodId, id, msg->event_code);
+
+        jvm->DetachCurrentThread();
     }
 #endif   // ZTS_ENABLE_JAVA
 #ifdef ZTS_ENABLE_PINVOKE

test/ExitTest.java

@@ -0,0 +1,77 @@
+import com.zerotier.sockets.*;
+
+//
+// Test for:
+// Java process does not exit after finishing libzt work
+// https://github.com/zerotier/libzt/issues/242
+//
+// Run and ensure that process exits
+//
+public class ExitTest {
+
+    public static void main(String[] args) throws InterruptedException {
+
+        long networkId = Long.parseUnsignedLong("ebe7fbd445e76ac6", 16);
+        String storagePath = "exittest_storage";
+
+        ZeroTierNode node = new ZeroTierNode();
+        node.initFromStorage(storagePath);
+        node.initSetEventHandler(new ZeroTierEventListener() {
+            @Override
+            public void onZeroTierEvent(long l, int eventCode) {
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NODE_UP) {
+                    System.err.println("ZTS_EVENT_NODE_UP");
+                }
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NODE_ONLINE) {
+                    System.err.println("ZTS_EVENT_NODE_ONLINE");
+                }
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NODE_OFFLINE) {
+                    System.err.println("ZTS_EVENT_NODE_OFFLINE");
+                }
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NODE_DOWN) {
+                    System.err.println("ZTS_EVENT_NODE_DOWN");
+                }
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NETWORK_READY_IP4) {
+                    System.err.println("ZTS_EVENT_NETWORK_READY_IP4");
+                }
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NETWORK_READY_IP6) {
+                    System.err.println("ZTS_EVENT_NETWORK_READY_IP6");
+                }
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NETWORK_DOWN) {
+                    System.err.println("ZTS_EVENT_NETWORK_DOWN");
+                }
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NETWORK_OK) {
+                    System.err.println("ZTS_EVENT_NETWORK_OK");
+                }
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NETWORK_ACCESS_DENIED) {
+                    System.err.println("ZTS_EVENT_NETWORK_ACCESS_DENIED");
+                }
+                if (eventCode == ZeroTierNative.ZTS_EVENT_NETWORK_NOT_FOUND) {
+                    System.err.println("ZTS_EVENT_NETWORK_NOT_FOUND");
+                }
+            }
+        });
+
+        System.err.println("start");
+        node.start();
+
+        System.err.println("delay until online");
+        while (!node.isOnline()) {
+            ZeroTierNative.zts_util_delay(50);
+        }
+        System.err.println("done delaying");
+
+        System.out.println("join");
+        node.join(networkId);
+
+        System.out.println("delaying until transport ready");
+        while (! node.isNetworkTransportReady(networkId)) {
+            ZeroTierNative.zts_util_delay(50);
+        }
+
+        System.err.println("stop");
+        node.stop();
+
+        System.err.println("exiting");
+    }
+}