Add more information to NotConnectedException

smack-core/src/main/java/org/jivesoftware/smack/SmackException.java

@@ -166,6 +166,11 @@ public class SmackException extends Exception {
         public NotConnectedException() {
             super("Client is not, or no longer, connected");
         }
+
+        public NotConnectedException(XMPPConnection connection, String details) {
+            super("The connection " + connection.toString() + " is no longer connected. "
+                            + details);
+        }
     }
 
     public static class IllegalStateChangeException extends SmackException {

smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java

@@ -1210,9 +1210,14 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
         }
 
         protected void throwNotConnectedExceptionIfDoneAndResumptionNotPossible() throws NotConnectedException {
-            if (done() && !isSmResumptionPossible()) {
+            final boolean done = done();
+            if (done) {
+                final boolean smResumptionPossbile = isSmResumptionPossible();
                 // Don't throw a NotConnectedException is there is an resumable stream available
-                throw new NotConnectedException();
+                if (!smResumptionPossbile) {
+                    throw new NotConnectedException(XMPPTCPConnection.this, "done=" + done
+                                    + " smResumptionPossible=" + smResumptionPossbile);
+                }
             }
         }