diff --git a/src/calibre/srv/pool.py b/src/calibre/srv/pool.py
index f8bcaca019..dd0fa8978e 100644
--- a/src/calibre/srv/pool.py
+++ b/src/calibre/srv/pool.py
@@ -104,7 +104,7 @@ class PluginPool(object):
         try:
             plugin.start(self.loop)
         except Exception:
-            self.loop.log.exception('Failed to start plugin: %s', self.plugin_name(plugin))
+            self.loop.log.exception('Failed to start plugin:', self.plugin_name(plugin))
 
     def start(self):
         for w in self.workers:
@@ -116,7 +116,7 @@ class PluginPool(object):
                 try:
                     w.plugin.stop()
                 except Exception:
-                    self.loop.log.exception('Failed to stop plugin: %s', self.plugin_name(w.plugin))
+                    self.loop.log.exception('Failed to stop plugin:', self.plugin_name(w.plugin))
         for w in self.workers:
             left = wait_till - monotonic()
             if left > 0:
diff --git a/src/calibre/utils/mdns.py b/src/calibre/utils/mdns.py
index bfc579d89d..294253ae7f 100644
--- a/src/calibre/utils/mdns.py
+++ b/src/calibre/utils/mdns.py
@@ -42,6 +42,7 @@ class AllIpAddressesGetter(Thread):
 #        print 'slept'
         _all_ip_addresses = self.get_all_ips()
 
+
 _ip_address_getter_thread = None
 
 
@@ -89,6 +90,7 @@ def verify_ipV4_address(ip_address):
             pass
     return result
 
+
 _ext_ip = None
 
 
@@ -97,7 +99,7 @@ def get_external_ip():
     if _ext_ip is None:
         from calibre.utils.ip_routing import get_default_route_src_address
         try:
-            _ext_ip = get_default_route_src_address()
+            _ext_ip = get_default_route_src_address() or _get_external_ip()
         except Exception:
             _ext_ip = _get_external_ip()
     return _ext_ip
@@ -138,6 +140,8 @@ def create_service(desc, type, port, properties, add_hostname, use_ip_address=No
         local_ip = use_ip_address
     else:
         local_ip = get_external_ip()
+    if not local_ip:
+        raise ValueError('Failed to determine local IP address to advertise via BonJour')
     type = type+'.local.'
     from calibre.utils.Zeroconf import ServiceInfo
     return ServiceInfo(type, desc+'.'+type,