diff --git a/src/calibre/gui2/actions/device.py b/src/calibre/gui2/actions/device.py
index f8515e7059..9b406ec4bc 100644
--- a/src/calibre/gui2/actions/device.py
+++ b/src/calibre/gui2/actions/device.py
@@ -17,23 +17,15 @@ from calibre.utils.smtp import config as email_config
 
 def local_url_for_content_server():
     from calibre.srv.opts import server_config
-    from calibre.utils.network import is_ipv6_addr, get_fallback_server_addr
+    from calibre.utils.network import format_addr_for_url, get_fallback_server_addr
 
     opts = server_config()
-    interface = opts.listen_on or get_fallback_server_addr()
-
-    addr_map = {'0.0.0.0': '127.0.0.1',
-                '::':      '::1'}
-    if interface in addr_map:
-        interface = addr_map[interface]
-
+    addr = opts.listen_on or get_fallback_server_addr()
+    addr = {'0.0.0.0': '127.0.0.1', '::': '::1'}.get(addr, addr)
     protocol = 'https' if opts.ssl_certfile and opts.ssl_keyfile else 'http'
     prefix = opts.url_prefix or ''
-
     port = opts.port
-    addr = f'[{interface}]' if is_ipv6_addr(interface) else f'{interface}'
-
-    return f'{protocol}://{addr}:{port}{prefix}'
+    return f'{protocol}://{format_addr_for_url(addr)}:{port}{prefix}'
 
 
 def open_in_browser():
diff --git a/src/calibre/gui2/preferences/server.py b/src/calibre/gui2/preferences/server.py
index d3812377dc..ffbf8e77e1 100644
--- a/src/calibre/gui2/preferences/server.py
+++ b/src/calibre/gui2/preferences/server.py
@@ -1299,23 +1299,12 @@ class ConfigWidget(ConfigWidgetBase):
         self.stopping_msg.accept()
 
     def test_server(self):
-        from calibre.utils.network import is_ipv6_addr, get_fallback_server_addr
-
+        from calibre.utils.network import format_addr_for_url, get_fallback_server_addr
         prefix = self.advanced_tab.get('url_prefix') or ''
         protocol = 'https' if self.advanced_tab.has_ssl else 'http'
-        lo = self.advanced_tab.get('listen_on') or get_fallback_server_addr()
-
-        addr_map = {'0.0.0.0': '127.0.0.1',
-                    '::':      '::1'}
-        if lo in addr_map:
-            lo = addr_map[lo]
-
-        if is_ipv6_addr(lo):
-            lo = f'[{lo}]'
-
-        url = '{protocol}://{interface}:{port}{prefix}'.format(
-            protocol=protocol, interface=lo,
-            port=self.main_tab.opt_port.value(), prefix=prefix)
+        addr = self.advanced_tab.get('listen_on') or get_fallback_server_addr()
+        addr = {'0.0.0.0': '127.0.0.1', '::': '::1'}.get(addr, addr)
+        url = f'{protocol}://{format_addr_for_url(addr)}:{self.main_tab.opt_port.value()}{prefix}'
         open_url(QUrl(url))
 
     def view_server_logs(self):
diff --git a/src/calibre/srv/loop.py b/src/calibre/srv/loop.py
index 61abdb35f4..425dbeeb74 100644
--- a/src/calibre/srv/loop.py
+++ b/src/calibre/srv/loop.py
@@ -509,17 +509,14 @@ class ServerLoop:
             self.setup_socket()
 
     def serve(self):
-        from calibre.utils.network import is_ipv6_addr
+        from calibre.utils.network import format_addr_for_url
 
         self.connection_map = {}
         if not self.socket_was_preactivated:
             self.socket.listen(min(socket.SOMAXCONN, 128))
         self.bound_address = ba = self.socket.getsockname()
         if isinstance(ba, tuple):
-            if is_ipv6_addr(ba[0]):
-                addr = f'[{ba[0]}]'
-            else:
-                addr = f'{ba[0]}'
+            addr = format_addr_for_url(str(ba[0]))
             ba_str = f'{addr}:' + ':'.join(map(str, ba[1:]))
         self.pool.start()
         with TemporaryDirectory(prefix='srv-') as tdir:
diff --git a/src/calibre/srv/opts.py b/src/calibre/srv/opts.py
index f6e3fd7e27..6ccdbfa4eb 100644
--- a/src/calibre/srv/opts.py
+++ b/src/calibre/srv/opts.py
@@ -112,8 +112,8 @@ raw_options = (
     _('The interface on which to listen for connections'),
     'listen_on', None,
     _('The default is to listen on all available IPv6 and IPv4 interfaces. You can change this to, for'
-    ' example, "127.0.0.1" to only listen for connections from the local machine, or'
-    ' to "::" to listen to all incoming IPv6 and IPv4 connections.'),
+    ' example, "127.0.0.1" to only listen for IPv4 connections from the local machine, or'
+    ' to "0.0.0.0" to listen to all incoming IPv4 connections.'),
 
     _('Fallback to auto-detected interface'),
     'fallback_to_detected_interface', True,
diff --git a/src/calibre/utils/mdns.py b/src/calibre/utils/mdns.py
index f2fbe1a190..b492c0573f 100644
--- a/src/calibre/utils/mdns.py
+++ b/src/calibre/utils/mdns.py
@@ -77,9 +77,6 @@ def _get_external_ip():
 
 
 def verify_ipV4_address(ip_address):
-    if ip_address == None:
-        return None
-
     result = None
     if ip_address != '0.0.0.0' and ip_address != '::':
         # do some more sanity checks on the address
@@ -87,7 +84,7 @@ def verify_ipV4_address(ip_address):
             socket.inet_aton(ip_address)
             if len(ip_address.split('.')) == 4:
                 result = ip_address
-        except OSError:
+        except Exception:
             # Not legal ip address
             pass
     return result
diff --git a/src/calibre/utils/network.py b/src/calibre/utils/network.py
index e2d071f594..213625c950 100644
--- a/src/calibre/utils/network.py
+++ b/src/calibre/utils/network.py
@@ -113,13 +113,17 @@ def is_ipv6_addr(addr):
     import socket
     try:
         socket.inet_pton(socket.AF_INET6, addr)
-        return True
-    except OSError:
+    except Exception:
         return False
+    return True
+
+
+def format_addr_for_url(addr):
+    if is_ipv6_addr(addr):
+        addr = f'[{addr}]'
+    return addr
+
 
 def get_fallback_server_addr():
     from socket import has_dualstack_ipv6
-    if has_dualstack_ipv6():
-        return '::'
-    else:
-        return '0.0.0.0'
+    return '::' if has_dualstack_ipv6() else '0.0.0.0'