Fix/885 update default bind address

docs/examples.circuit_relay.rst

@@ -41,7 +41,7 @@ Create a file named ``relay_node.py`` with the following content:
     logger = logging.getLogger("relay_node")
 
     async def run_relay():
-        listen_addr = multiaddr.Multiaddr("/ip4/0.0.0.0/tcp/9000")
+        listen_addr = multiaddr.Multiaddr("/ip4/127.0.0.1/tcp/9000")
         host = new_host()
 
         config = RelayConfig(
@@ -139,7 +139,7 @@ Create a file named ``destination_node.py`` with the following content:
         Run a simple destination node that accepts connections.
         This is a simplified version that doesn't use the relay functionality.
         """
-        listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/9001")
+        listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/9001")
         host = new_host()
 
         # Configure as a relay receiver (stop)
@@ -259,7 +259,7 @@ Create a file named ``source_node.py`` with the following content:
 
     async def run_source(relay_peer_id=None, destination_peer_id=None):
         # Create a libp2p host
-        listen_addr = multiaddr.Multiaddr("/ip4/0.0.0.0/tcp/9002")
+        listen_addr = multiaddr.Multiaddr("/ip4/127.0.0.1/tcp/9002")
         host = new_host()
 
         # Configure as a relay client
@@ -428,7 +428,7 @@ Running the Example
        Relay node multiaddr: /ip4/127.0.0.1/tcp/9000/p2p/QmaUigQJ9nJERa6GaZuyfaiX91QjYwoQJ46JS3k7ys7SLx
        ==================================================
 
-       Listening on: [<Multiaddr /ip4/0.0.0.0/tcp/9000/p2p/QmaUigQJ9nJERa6GaZuyfaiX91QjYwoQJ46JS3k7ys7SLx>]
+       Listening on: [<Multiaddr /ip4/127.0.0.1/tcp/9000/p2p/QmaUigQJ9nJERa6GaZuyfaiX91QjYwoQJ46JS3k7ys7SLx>]
        Protocol service started
        Relay service started successfully
        Relay limits: RelayLimits(duration=3600, data=10485760, max_circuit_conns=8, max_reservations=4)
@@ -447,7 +447,7 @@ Running the Example
        Use this ID in the source node: QmPBr38KeQG2ibyL4fxq6yJWpfoVNCqJMHBdNyn1Qe4h5s
        ==================================================
 
-       Listening on: [<Multiaddr /ip4/0.0.0.0/tcp/9001/p2p/QmPBr38KeQG2ibyL4fxq6yJWpfoVNCqJMHBdNyn1Qe4h5s>]
+       Listening on: [<Multiaddr /ip4/127.0.0.1/tcp/9001/p2p/QmPBr38KeQG2ibyL4fxq6yJWpfoVNCqJMHBdNyn1Qe4h5s>]
        Registered echo protocol handler
        Protocol service started
        Transport created
@@ -469,7 +469,7 @@ Running the Example
 
        $ python source_node.py
        Source node started with ID: QmPyM56cgmFoHTgvMgGfDWRdVRQznmxCDDDg2dJ8ygVXj3
-       Listening on: [<Multiaddr /ip4/0.0.0.0/tcp/9002/p2p/QmPyM56cgmFoHTgvMgGfDWRdVRQznmxCDDDg2dJ8ygVXj3>]
+       Listening on: [<Multiaddr /ip4/127.0.0.1/tcp/9002/p2p/QmPyM56cgmFoHTgvMgGfDWRdVRQznmxCDDDg2dJ8ygVXj3>]
        Protocol service started
        No relay peer ID provided. Please enter the relay\'s peer ID:
        Enter relay peer ID: QmaUigQJ9nJERa6GaZuyfaiX91QjYwoQJ46JS3k7ys7SLx

docs/examples.identify.rst

@@ -12,7 +12,7 @@ This example demonstrates how to use the libp2p ``identify`` protocol.
     $ identify-demo
     First host listening. Run this from another console:
 
-    identify-demo -p 8889 -d /ip4/0.0.0.0/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
+    identify-demo -p 8889 -d /ip4/127.0.0.1/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
 
     Waiting for incoming identify request...
 
@@ -21,13 +21,13 @@ folder and paste it in:
 
 .. code-block:: console
 
-    $ identify-demo -p 8889 -d /ip4/0.0.0.0/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
-    dialer (host_b) listening on /ip4/0.0.0.0/tcp/8889
+    $ identify-demo -p 8889 -d /ip4/127.0.0.1/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
+    dialer (host_b) listening on /ip4/127.0.0.1/tcp/8889
     Second host connecting to peer: QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
     Starting identify protocol...
     Identify response:
     Public Key (Base64): CAASpgIwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDC6c/oNPP9X13NDQ3Xrlp3zOj+ErXIWb/A4JGwWchiDBwMhMslEX3ct8CqI0BqUYKuwdFjowqqopOJ3cS2MlqtGaiP6Dg9bvGqSDoD37BpNaRVNcebRxtB0nam9SQy3PYLbHAmz0vR4ToSiL9OLRORnGOxCtHBuR8ZZ5vS0JEni8eQMpNa7IuXwyStnuty/QjugOZudBNgYSr8+9gH722KTjput5IRL7BrpIdd4HNXGVRm4b9BjNowvHu404x3a/ifeNblpy/FbYyFJEW0looygKF7hpRHhRbRKIDZt2BqOfT1sFkbqsHE85oY859+VMzP61YELgvGwai2r7KcjkW/AgMBAAE=
-    Listen Addresses: ['/ip4/0.0.0.0/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM']
+    Listen Addresses: ['/ip4/127.0.0.1/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM']
     Protocols: ['/ipfs/id/1.0.0', '/ipfs/ping/1.0.0']
     Observed Address: ['/ip4/127.0.0.1/tcp/38082']
     Protocol Version: ipfs/0.1.0

docs/examples.identify_push.rst

@@ -34,11 +34,11 @@ There is also a more interactive version of the example which runs as separate l
     ==== Starting Identify-Push Listener on port 8888 ====
 
     Listener host ready!
-    Listening on: /ip4/0.0.0.0/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
+    Listening on: /ip4/127.0.0.1/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
     Peer ID: QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
 
     Run dialer with command:
-    identify-push-listener-dialer-demo -d /ip4/0.0.0.0/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
+    identify-push-listener-dialer-demo -d /ip4/127.0.0.1/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
 
     Waiting for incoming connections... (Ctrl+C to exit)
 
@@ -47,12 +47,12 @@ folder and paste it in:
 
 .. code-block:: console
 
-    $ identify-push-listener-dialer-demo -d /ip4/0.0.0.0/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
+    $ identify-push-listener-dialer-demo -d /ip4/127.0.0.1/tcp/8888/p2p/QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
 
     ==== Starting Identify-Push Dialer on port 8889 ====
 
     Dialer host ready!
-    Listening on: /ip4/0.0.0.0/tcp/8889/p2p/QmZyXwVuTaBcDeRsSkJpOpWrSt
+    Listening on: /ip4/127.0.0.1/tcp/8889/p2p/QmZyXwVuTaBcDeRsSkJpOpWrSt
 
     Connecting to peer: QmUiN4R3fNrCoQugGgmmb3v35neMEjKFNrsbNGVDsRHWpM
     Successfully connected to listener!

docs/examples.pubsub.rst

@@ -15,7 +15,7 @@ This example demonstrates how to create a chat application using libp2p's PubSub
     2025-04-06 23:59:17,471 - pubsub-demo - INFO - Your selected topic is: pubsub-chat
     2025-04-06 23:59:17,472 - pubsub-demo - INFO - Using random available port: 33269
     2025-04-06 23:59:17,490 - pubsub-demo - INFO - Node started with peer ID: QmcJnocH1d1tz3Zp4MotVDjNfNFawXHw2dpB9tMYGTXJp7
-    2025-04-06 23:59:17,490 - pubsub-demo - INFO - Listening on: /ip4/0.0.0.0/tcp/33269
+    2025-04-06 23:59:17,490 - pubsub-demo - INFO - Listening on: /ip4/127.0.0.1/tcp/33269
     2025-04-06 23:59:17,490 - pubsub-demo - INFO - Initializing PubSub and GossipSub...
     2025-04-06 23:59:17,491 - pubsub-demo - INFO - Pubsub and GossipSub services started.
     2025-04-06 23:59:17,491 - pubsub-demo - INFO - Pubsub ready.
@@ -35,7 +35,7 @@ Copy the line that starts with ``pubsub-demo -d``, open a new terminal and paste
     2025-04-07 00:00:59,846 - pubsub-demo - INFO - Your selected topic is: pubsub-chat
     2025-04-07 00:00:59,846 - pubsub-demo - INFO - Using random available port: 51977
     2025-04-07 00:00:59,864 - pubsub-demo - INFO - Node started with peer ID: QmYQKCm95Ut1aXsjHmWVYqdaVbno1eKTYC8KbEVjqUaKaQ
-    2025-04-07 00:00:59,864 - pubsub-demo - INFO - Listening on: /ip4/0.0.0.0/tcp/51977
+    2025-04-07 00:00:59,864 - pubsub-demo - INFO - Listening on: /ip4/127.0.0.1/tcp/51977
     2025-04-07 00:00:59,864 - pubsub-demo - INFO - Initializing PubSub and GossipSub...
     2025-04-07 00:00:59,864 - pubsub-demo - INFO - Pubsub and GossipSub services started.
     2025-04-07 00:00:59,865 - pubsub-demo - INFO - Pubsub ready.

docs/examples.random_walk.rst

@@ -23,7 +23,7 @@ The Random Walk implementation performs the following key operations:
     2025-08-12 19:51:25,424 - random-walk-example - INFO - Mode: server, Port: 0 Demo interval: 30s
     2025-08-12 19:51:25,426 - random-walk-example - INFO - Starting server node on port 45123
     2025-08-12 19:51:25,426 - random-walk-example - INFO - Node peer ID: 16Uiu2HAm7EsNv5vvjPAehGAVfChjYjD63ZHyWogQRdzntSbAg9ef
-    2025-08-12 19:51:25,426 - random-walk-example - INFO - Node address: /ip4/0.0.0.0/tcp/45123/p2p/16Uiu2HAm7EsNv5vvjPAehGAVfChjYjD63ZHyWogQRdzntSbAg9ef
+    2025-08-12 19:51:25,426 - random-walk-example - INFO - Node address: /ip4/127.0.0.1/tcp/45123/p2p/16Uiu2HAm7EsNv5vvjPAehGAVfChjYjD63ZHyWogQRdzntSbAg9ef
     2025-08-12 19:51:25,427 - random-walk-example - INFO - Initial routing table size: 0
     2025-08-12 19:51:25,427 - random-walk-example - INFO - DHT service started in SERVER mode
     2025-08-12 19:51:25,430 - libp2p.discovery.random_walk.rt_refresh_manager - INFO - RT Refresh Manager started

examples/advanced/network_discover.py

@@ -18,7 +18,7 @@
 except ImportError:
     # Fallbacks if utilities are missing
     def get_available_interfaces(port: int, protocol: str = "tcp"):
-        return [Multiaddr(f"/ip4/0.0.0.0/{protocol}/{port}")]
+        return [Multiaddr(f"/ip4/127.0.0.1/{protocol}/{port}")]
 
     def expand_wildcard_address(addr: Multiaddr, port: int | None = None):
         if port is None:
@@ -27,7 +27,7 @@ def expand_wildcard_address(addr: Multiaddr, port: int | None = None):
         return [Multiaddr(addr_str + f"/{port}")]
 
     def get_optimal_binding_address(port: int, protocol: str = "tcp"):
-        return Multiaddr(f"/ip4/0.0.0.0/{protocol}/{port}")
+        return Multiaddr(f"/ip4/127.0.0.1/{protocol}/{port}")
 
 
 def main() -> None:

examples/bootstrap/bootstrap.py

@@ -59,7 +59,7 @@ async def run(port: int, bootstrap_addrs: list[str]) -> None:
     key_pair = create_new_key_pair(secret)
 
     # Create listen address
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Register peer discovery handler
     peerDiscovery.register_peer_discovered_handler(on_peer_discovery)

examples/chat/chat.py

@@ -40,7 +40,7 @@ async def write_data(stream: INetStream) -> None:
 
 
 async def run(port: int, destination: str) -> None:
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
     host = new_host()
     async with host.run(listen_addrs=[listen_addr]), trio.open_nursery() as nursery:
         # Start the peer-store cleanup task

examples/doc-examples/example_encryption_insecure.py

@@ -40,7 +40,7 @@ async def main():
 
     # Configure the listening address
     port = 8000
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Start the host
     async with host.run(listen_addrs=[listen_addr]):

examples/doc-examples/example_encryption_noise.py

@@ -41,7 +41,7 @@ async def main():
 
     # Configure the listening address
     port = 8000
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Start the host
     async with host.run(listen_addrs=[listen_addr]):

examples/doc-examples/example_encryption_secio.py

@@ -34,7 +34,7 @@ async def main():
 
     # Configure the listening address
     port = 8000
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Start the host
     async with host.run(listen_addrs=[listen_addr]):

examples/doc-examples/example_multiplexer.py

@@ -41,7 +41,7 @@ async def main():
 
     # Configure the listening address
     port = 8000
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Start the host
     async with host.run(listen_addrs=[listen_addr]):

examples/doc-examples/example_net_stream.py

@@ -173,7 +173,7 @@ async def run_enhanced_demo(
     """
     Run enhanced echo demo with NetStream state management.
     """
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Generate or use provided key
     if seed:

examples/doc-examples/example_peer_discovery.py

@@ -44,7 +44,7 @@ async def main():
 
     # Configure the listening address
     port = 8000
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Start the host
     async with host.run(listen_addrs=[listen_addr]):

examples/doc-examples/example_running.py

@@ -41,7 +41,7 @@ async def main():
 
     # Configure the listening address
     port = 8000
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Start the host
     async with host.run(listen_addrs=[listen_addr]):

examples/doc-examples/example_transport.py

@@ -21,7 +21,7 @@ async def main():
 
     # Configure the listening address
     port = 8000
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Start the host
     async with host.run(listen_addrs=[listen_addr]):

examples/identify/identify.py

@@ -58,7 +58,7 @@ def print_identify_response(identify_response: Identify):
 
 
 async def run(port: int, destination: str, use_varint_format: bool = True) -> None:
-    localhost_ip = "0.0.0.0"
+    localhost_ip = "127.0.0.1"
 
     if not destination:
         # Create first host (listener)
@@ -79,10 +79,9 @@ async def run(port: int, destination: str, use_varint_format: bool = True) -> No
             # Start the peer-store cleanup task
             nursery.start_soon(host_a.get_peerstore().start_cleanup_task, 60)
 
-            # Get the actual address and replace 0.0.0.0 with 127.0.0.1 for client
-            # connections
+            # Get the actual address
             server_addr = str(host_a.get_addrs()[0])
-            client_addr = server_addr.replace("/ip4/0.0.0.0/", "/ip4/127.0.0.1/")
+            client_addr = server_addr
 
             format_name = "length-prefixed" if use_varint_format else "raw protobuf"
             format_flag = "--raw-format" if not use_varint_format else ""

examples/identify_push/identify_push_listener_dialer.py

@@ -216,7 +216,7 @@ async def run_listener(
     )
 
     # Start listening
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     try:
         async with host.run([listen_addr]):
@@ -275,7 +275,7 @@ async def run_dialer(
     )
 
     # Start listening on a different port
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     async with host.run([listen_addr]):
         logger.info("Dialer host ready!")

examples/mDNS/mDNS.py

@@ -33,7 +33,7 @@ def onPeerDiscovery(peerinfo: PeerInfo):
 async def run(port: int) -> None:
     secret = secrets.token_bytes(32)
     key_pair = create_new_key_pair(secret)
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     peerDiscovery.register_peer_discovered_handler(onPeerDiscovery)
 

examples/ping/ping.py

@@ -55,7 +55,7 @@ async def send_ping(stream: INetStream) -> None:
 
 
 async def run(port: int, destination: str) -> None:
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
     host = new_host(listen_addrs=[listen_addr])
 
     async with host.run(listen_addrs=[listen_addr]), trio.open_nursery() as nursery:

examples/pubsub/pubsub.py

@@ -109,7 +109,7 @@ async def run(topic: str, destination: str | None, port: int | None) -> None:
         port = find_free_port()
         logger.info(f"Using random available port: {port}")
 
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    listen_addr = multiaddr.Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
     # Create a new libp2p host
     host = new_host(

examples/random_walk/random_walk.py

@@ -130,7 +130,7 @@ async def run_node(port: int, mode: str, demo_interval: int = 30) -> None:
         # Create host and DHT
         key_pair = create_new_key_pair(secrets.token_bytes(32))
         host = new_host(key_pair=key_pair, bootstrap=DEFAULT_BOOTSTRAP_NODES)
-        listen_addr = Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+        listen_addr = Multiaddr(f"/ip4/127.0.0.1/tcp/{port}")
 
         async with host.run(listen_addrs=[listen_addr]), trio.open_nursery() as nursery:
             # Start maintenance tasks
@@ -139,7 +139,7 @@ async def run_node(port: int, mode: str, demo_interval: int = 30) -> None:
 
             peer_id = host.get_id().pretty()
             logger.info(f"Node peer ID: {peer_id}")
-            logger.info(f"Node address: /ip4/0.0.0.0/tcp/{port}/p2p/{peer_id}")
+            logger.info(f"Node address: /ip4/127.0.0.1/tcp/{port}/p2p/{peer_id}")
 
             # Create and start DHT with Random Walk enabled
             dht = KadDHT(host, dht_mode, enable_random_walk=True)

libp2p/utils/address_validation.py

@@ -99,7 +99,7 @@ def get_available_interfaces(port: int, protocol: str = "tcp") -> list[Multiaddr
 
     # Fallback if nothing discovered
     if not addrs:
-        addrs.append(Multiaddr(f"/ip4/0.0.0.0/{protocol}/{port}"))
+        addrs.append(Multiaddr(f"/ip4/127.0.0.1/{protocol}/{port}"))
 
     return addrs
 
@@ -148,8 +148,8 @@ def is_non_loopback(ma: Multiaddr) -> bool:
         if "/ip4/127." in str(c) or "/ip6/::1" in str(c):
             return c
 
-    # As a final fallback, produce a wildcard
-    return Multiaddr(f"/ip4/0.0.0.0/{protocol}/{port}")
+    # As a final fallback, produce a loopback address
+    return Multiaddr(f"/ip4/127.0.0.1/{protocol}/{port}")
 
 
 __all__ = [

newsfragments/885.feature.rst

@@ -0,0 +1,2 @@
+Enhanced security by defaulting to loopback address (127.0.0.1) instead of wildcard binding.
+All examples and core modules now use secure default addresses to prevent unintended public exposure.