Merge branch 'main' into dependency-chore

examples/advanced/network_discover.py

@@ -0,0 +1,63 @@
+"""
+Advanced demonstration of Thin Waist address handling.
+
+Run:
+    python -m examples.advanced.network_discovery
+"""
+
+from __future__ import annotations
+
+from multiaddr import Multiaddr
+
+try:
+    from libp2p.utils.address_validation import (
+        expand_wildcard_address,
+        get_available_interfaces,
+        get_optimal_binding_address,
+    )
+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}")]
+
+    def expand_wildcard_address(addr: Multiaddr, port: int | None = None):
+        if port is None:
+            return [addr]
+        addr_str = str(addr).rsplit("/", 1)[0]
+        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}")
+
+
+def main() -> None:
+    port = 8080
+    interfaces = get_available_interfaces(port)
+    print(f"Discovered interfaces for port {port}:")
+    for a in interfaces:
+        print(f"  - {a}")
+
+    wildcard_v4 = Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    expanded_v4 = expand_wildcard_address(wildcard_v4)
+    print("\nExpanded IPv4 wildcard:")
+    for a in expanded_v4:
+        print(f"  - {a}")
+
+    wildcard_v6 = Multiaddr(f"/ip6/::/tcp/{port}")
+    expanded_v6 = expand_wildcard_address(wildcard_v6)
+    print("\nExpanded IPv6 wildcard:")
+    for a in expanded_v6:
+        print(f"  - {a}")
+
+    print("\nOptimal binding address heuristic result:")
+    print(f"  -> {get_optimal_binding_address(port)}")
+
+    override_port = 9000
+    overridden = expand_wildcard_address(wildcard_v4, port=override_port)
+    print(f"\nPort override expansion to {override_port}:")
+    for a in overridden:
+        print(f"  - {a}")
+
+
+if __name__ == "__main__":
+    main()

examples/echo/echo.py

@@ -1,4 +1,6 @@
 import argparse
+import random
+import secrets
 
 import multiaddr
 import trio
@@ -12,40 +14,54 @@ from libp2p.crypto.secp256k1 import (
 from libp2p.custom_types import (
     TProtocol,
 )
+from libp2p.network.stream.exceptions import (
+    StreamEOF,
+)
 from libp2p.network.stream.net_stream import (
     INetStream,
 )
 from libp2p.peer.peerinfo import (
     info_from_p2p_addr,
 )
+from libp2p.utils.address_validation import (
+    find_free_port,
+    get_available_interfaces,
+)
 
 PROTOCOL_ID = TProtocol("/echo/1.0.0")
 MAX_READ_LEN = 2**32 - 1
 
 
 async def _echo_stream_handler(stream: INetStream) -> None:
-    # Wait until EOF
-    msg = await stream.read(MAX_READ_LEN)
-    await stream.write(msg)
-    await stream.close()
+    try:
+        peer_id = stream.muxed_conn.peer_id
+        print(f"Received connection from {peer_id}")
+        # Wait until EOF
+        msg = await stream.read(MAX_READ_LEN)
+        print(f"Echoing message: {msg.decode('utf-8')}")
+        await stream.write(msg)
+    except StreamEOF:
+        print("Stream closed by remote peer.")
+    except Exception as e:
+        print(f"Error in echo handler: {e}")
+    finally:
+        await stream.close()
 
 
 async def run(port: int, destination: str, seed: int | None = None) -> None:
-    listen_addr = multiaddr.Multiaddr(f"/ip4/0.0.0.0/tcp/{port}")
+    if port <= 0:
+        port = find_free_port()
+    listen_addr = get_available_interfaces(port)
 
     if seed:
-        import random
-
         random.seed(seed)
         secret_number = random.getrandbits(32 * 8)
         secret = secret_number.to_bytes(length=32, byteorder="big")
     else:
-        import secrets
-
         secret = secrets.token_bytes(32)
 
     host = new_host(key_pair=create_new_key_pair(secret))
-    async with host.run(listen_addrs=[listen_addr]), trio.open_nursery() as nursery:
+    async with host.run(listen_addrs=listen_addr), trio.open_nursery() as nursery:
         # Start the peer-store cleanup task
         nursery.start_soon(host.get_peerstore().start_cleanup_task, 60)
 
@@ -54,10 +70,15 @@ async def run(port: int, destination: str, seed: int | None = None) -> None:
         if not destination:  # its the server
             host.set_stream_handler(PROTOCOL_ID, _echo_stream_handler)
 
+            # Print all listen addresses with peer ID (JS parity)
+            print("Listener ready, listening on:\n")
+            peer_id = host.get_id().to_string()
+            for addr in listen_addr:
+                print(f"{addr}/p2p/{peer_id}")
+
             print(
-                "Run this from the same folder in another console:\n\n"
-                f"echo-demo "
-                f"-d {host.get_addrs()[0]}\n"
+                "\nRun this from the same folder in another console:\n\n"
+                f"echo-demo -d {host.get_addrs()[0]}\n"
             )
             print("Waiting for incoming connections...")
             await trio.sleep_forever()

examples/pubsub/pubsub.py

@@ -1,6 +1,5 @@
 import argparse
 import logging
-import socket
 
 import base58
 import multiaddr
@@ -31,6 +30,9 @@ from libp2p.stream_muxer.mplex.mplex import (
 from libp2p.tools.async_service.trio_service import (
     background_trio_service,
 )
+from libp2p.utils.address_validation import (
+    find_free_port,
+)
 
 # Configure logging
 logging.basicConfig(
@@ -77,13 +79,6 @@ async def publish_loop(pubsub, topic, termination_event):
             await trio.sleep(1)  # Avoid tight loop on error
 
 
-def find_free_port():
-    """Find a free port on localhost."""
-    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
-        s.bind(("", 0))  # Bind to a free port provided by the OS
-        return s.getsockname()[1]
-
-
 async def monitor_peer_topics(pubsub, nursery, termination_event):
     """
     Monitor for new topics that peers are subscribed to and

libp2p/network/swarm.py

@@ -249,9 +249,11 @@ class Swarm(Service, INetworkService):
         # We need to wait until `self.listener_nursery` is created.
         await self.event_listener_nursery_created.wait()
 
+        success_count = 0
         for maddr in multiaddrs:
             if str(maddr) in self.listeners:
-                return True
+                success_count += 1
+                continue
 
             async def conn_handler(
                 read_write_closer: ReadWriteCloser, maddr: Multiaddr = maddr
@@ -302,13 +304,14 @@ class Swarm(Service, INetworkService):
                 # Call notifiers since event occurred
                 await self.notify_listen(maddr)
 
-                return True
+                success_count += 1
+                logger.debug("successfully started listening on: %s", maddr)
             except OSError:
                 # Failed. Continue looping.
                 logger.debug("fail to listen on: %s", maddr)
 
-        # No maddr succeeded
-        return False
+        # Return true if at least one address succeeded
+        return success_count > 0
 
     async def close(self) -> None:
         """

libp2p/utils/__init__.py

@@ -15,6 +15,13 @@ from libp2p.utils.version import (
     get_agent_version,
 )
 
+from libp2p.utils.address_validation import (
+    get_available_interfaces,
+    get_optimal_binding_address,
+    expand_wildcard_address,
+    find_free_port,
+)
+
 __all__ = [
     "decode_uvarint_from_stream",
     "encode_delim",
@@ -26,4 +33,8 @@ __all__ = [
     "decode_varint_from_bytes",
     "decode_varint_with_size",
     "read_length_prefixed_protobuf",
+    "get_available_interfaces",
+    "get_optimal_binding_address",
+    "expand_wildcard_address",
+    "find_free_port",
 ]

libp2p/utils/address_validation.py

@@ -0,0 +1,160 @@
+from __future__ import annotations
+
+import socket
+
+from multiaddr import Multiaddr
+
+try:
+    from multiaddr.utils import (  # type: ignore
+        get_network_addrs,
+        get_thin_waist_addresses,
+    )
+
+    _HAS_THIN_WAIST = True
+except ImportError:  # pragma: no cover - only executed in older environments
+    _HAS_THIN_WAIST = False
+    get_thin_waist_addresses = None  # type: ignore
+    get_network_addrs = None  # type: ignore
+
+
+def _safe_get_network_addrs(ip_version: int) -> list[str]:
+    """
+    Internal safe wrapper. Returns a list of IP addresses for the requested IP version.
+    Falls back to minimal defaults when Thin Waist helpers are missing.
+
+    :param ip_version: 4 or 6
+    """
+    if _HAS_THIN_WAIST and get_network_addrs:
+        try:
+            return get_network_addrs(ip_version) or []
+        except Exception:  # pragma: no cover - defensive
+            return []
+    # Fallback behavior (very conservative)
+    if ip_version == 4:
+        return ["127.0.0.1"]
+    if ip_version == 6:
+        return ["::1"]
+    return []
+
+
+def find_free_port() -> int:
+    """Find a free port on localhost."""
+    with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
+        s.bind(("", 0))  # Bind to a free port provided by the OS
+        return s.getsockname()[1]
+
+
+def _safe_expand(addr: Multiaddr, port: int | None = None) -> list[Multiaddr]:
+    """
+    Internal safe expansion wrapper. Returns a list of Multiaddr objects.
+    If Thin Waist isn't available, returns [addr] (identity).
+    """
+    if _HAS_THIN_WAIST and get_thin_waist_addresses:
+        try:
+            if port is not None:
+                return get_thin_waist_addresses(addr, port=port) or []
+            return get_thin_waist_addresses(addr) or []
+        except Exception:  # pragma: no cover - defensive
+            return [addr]
+    return [addr]
+
+
+def get_available_interfaces(port: int, protocol: str = "tcp") -> list[Multiaddr]:
+    """
+    Discover available network interfaces (IPv4 + IPv6 if supported) for binding.
+
+    :param port: Port number to bind to.
+    :param protocol: Transport protocol (e.g., "tcp" or "udp").
+    :return: List of Multiaddr objects representing candidate interface addresses.
+    """
+    addrs: list[Multiaddr] = []
+
+    # IPv4 enumeration
+    seen_v4: set[str] = set()
+
+    for ip in _safe_get_network_addrs(4):
+        seen_v4.add(ip)
+        addrs.append(Multiaddr(f"/ip4/{ip}/{protocol}/{port}"))
+
+    # Ensure IPv4 loopback is always included when IPv4 interfaces are discovered
+    if seen_v4 and "127.0.0.1" not in seen_v4:
+        addrs.append(Multiaddr(f"/ip4/127.0.0.1/{protocol}/{port}"))
+
+    # TODO: IPv6 support temporarily disabled due to libp2p handshake issues
+    # IPv6 connections fail during protocol negotiation (SecurityUpgradeFailure)
+    # Re-enable IPv6 support once the following issues are resolved:
+    # - libp2p security handshake over IPv6
+    # - multiselect protocol over IPv6
+    # - connection establishment over IPv6
+    #
+    # seen_v6: set[str] = set()
+    # for ip in _safe_get_network_addrs(6):
+    #     seen_v6.add(ip)
+    #     addrs.append(Multiaddr(f"/ip6/{ip}/{protocol}/{port}"))
+    #
+    # # Always include IPv6 loopback for testing purposes when IPv6 is available
+    # # This ensures IPv6 functionality can be tested even without global IPv6 addresses
+    # if "::1" not in seen_v6:
+    #     addrs.append(Multiaddr(f"/ip6/::1/{protocol}/{port}"))
+
+    # Fallback if nothing discovered
+    if not addrs:
+        addrs.append(Multiaddr(f"/ip4/0.0.0.0/{protocol}/{port}"))
+
+    return addrs
+
+
+def expand_wildcard_address(
+    addr: Multiaddr, port: int | None = None
+) -> list[Multiaddr]:
+    """
+    Expand a wildcard (e.g. /ip4/0.0.0.0/tcp/0) into all concrete interfaces.
+
+    :param addr: Multiaddr to expand.
+    :param port: Optional override for port selection.
+    :return: List of concrete Multiaddr instances.
+    """
+    expanded = _safe_expand(addr, port=port)
+    if not expanded:  # Safety fallback
+        return [addr]
+    return expanded
+
+
+def get_optimal_binding_address(port: int, protocol: str = "tcp") -> Multiaddr:
+    """
+    Choose an optimal address for an example to bind to:
+    - Prefer non-loopback IPv4
+    - Then non-loopback IPv6
+    - Fallback to loopback
+    - Fallback to wildcard
+
+    :param port: Port number.
+    :param protocol: Transport protocol.
+    :return: A single Multiaddr chosen heuristically.
+    """
+    candidates = get_available_interfaces(port, protocol)
+
+    def is_non_loopback(ma: Multiaddr) -> bool:
+        s = str(ma)
+        return not ("/ip4/127." in s or "/ip6/::1" in s)
+
+    for c in candidates:
+        if "/ip4/" in str(c) and is_non_loopback(c):
+            return c
+    for c in candidates:
+        if "/ip6/" in str(c) and is_non_loopback(c):
+            return c
+    for c in candidates:
+        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}")
+
+
+__all__ = [
+    "get_available_interfaces",
+    "get_optimal_binding_address",
+    "expand_wildcard_address",
+    "find_free_port",
+]

newsfragments/811.feature.rst

@@ -0,0 +1 @@
+ Added Thin Waist address validation utilities (with support for interface enumeration, optimal binding, and wildcard expansion).

newsfragments/811.internal.rst

@@ -0,0 +1,7 @@
+Add Thin Waist address validation utilities and integrate into echo example
+
+- Add ``libp2p/utils/address_validation.py`` with dynamic interface discovery
+- Implement ``get_available_interfaces()``, ``get_optimal_binding_address()``, and ``expand_wildcard_address()``
+- Update echo example to use dynamic address discovery instead of hardcoded wildcard
+- Add safe fallbacks for environments lacking Thin Waist support
+- Temporarily disable IPv6 support due to libp2p handshake issues (TODO: re-enable when resolved)

newsfragments/863.bugfix.rst

@@ -0,0 +1,5 @@
+Fix multi-address listening bug in swarm.listen()
+
+- Fix early return in swarm.listen() that prevented listening on all addresses
+- Add comprehensive tests for multi-address listening functionality
+- Ensure all available interfaces are properly bound and connectable

tests/core/network/test_swarm.py

@@ -16,6 +16,9 @@ from libp2p.network.exceptions import (
 from libp2p.network.swarm import (
     Swarm,
 )
+from libp2p.tools.async_service import (
+    background_trio_service,
+)
 from libp2p.tools.utils import (
     connect_swarm,
 )
@@ -184,3 +187,116 @@ def test_new_swarm_quic_multiaddr_raises():
     addr = Multiaddr("/ip4/127.0.0.1/udp/9999/quic")
     with pytest.raises(ValueError, match="QUIC not yet supported"):
         new_swarm(listen_addrs=[addr])
+
+
+@pytest.mark.trio
+async def test_swarm_listen_multiple_addresses(security_protocol):
+    """Test that swarm can listen on multiple addresses simultaneously."""
+    from libp2p.utils.address_validation import get_available_interfaces
+
+    # Get multiple addresses to listen on
+    listen_addrs = get_available_interfaces(0)  # Let OS choose ports
+
+    # Create a swarm and listen on multiple addresses
+    swarm = SwarmFactory.build(security_protocol=security_protocol)
+    async with background_trio_service(swarm):
+        # Listen on all addresses
+        success = await swarm.listen(*listen_addrs)
+        assert success, "Should successfully listen on at least one address"
+
+        # Check that we have listeners for the addresses
+        actual_listeners = list(swarm.listeners.keys())
+        assert len(actual_listeners) > 0, "Should have at least one listener"
+
+        # Verify that all successful listeners are in the listeners dict
+        successful_count = 0
+        for addr in listen_addrs:
+            addr_str = str(addr)
+            if addr_str in actual_listeners:
+                successful_count += 1
+                # This address successfully started listening
+                listener = swarm.listeners[addr_str]
+                listener_addrs = listener.get_addrs()
+                assert len(listener_addrs) > 0, (
+                    f"Listener for {addr} should have addresses"
+                )
+
+                # Check that the listener address matches the expected address
+                # (port might be different if we used port 0)
+                expected_ip = addr.value_for_protocol("ip4")
+                expected_protocol = addr.value_for_protocol("tcp")
+                if expected_ip and expected_protocol:
+                    found_matching = False
+                    for listener_addr in listener_addrs:
+                        if (
+                            listener_addr.value_for_protocol("ip4") == expected_ip
+                            and listener_addr.value_for_protocol("tcp") is not None
+                        ):
+                            found_matching = True
+                            break
+                    assert found_matching, (
+                        f"Listener for {addr} should have matching IP"
+                    )
+
+        assert successful_count == len(listen_addrs), (
+            f"All {len(listen_addrs)} addresses should be listening, "
+            f"but only {successful_count} succeeded"
+        )
+
+
+@pytest.mark.trio
+async def test_swarm_listen_multiple_addresses_connectivity(security_protocol):
+    """Test that real libp2p connections can be established to all listening addresses."""  # noqa: E501
+    from libp2p.peer.peerinfo import info_from_p2p_addr
+    from libp2p.utils.address_validation import get_available_interfaces
+
+    # Get multiple addresses to listen on
+    listen_addrs = get_available_interfaces(0)  # Let OS choose ports
+
+    # Create a swarm and listen on multiple addresses
+    swarm1 = SwarmFactory.build(security_protocol=security_protocol)
+    async with background_trio_service(swarm1):
+        # Listen on all addresses
+        success = await swarm1.listen(*listen_addrs)
+        assert success, "Should successfully listen on at least one address"
+
+        # Verify all available interfaces are listening
+        assert len(swarm1.listeners) == len(listen_addrs), (
+            f"All {len(listen_addrs)} interfaces should be listening, "
+            f"but only {len(swarm1.listeners)} are"
+        )
+
+        # Create a second swarm to test connections
+        swarm2 = SwarmFactory.build(security_protocol=security_protocol)
+        async with background_trio_service(swarm2):
+            # Test connectivity to each listening address using real libp2p connections
+            for addr_str, listener in swarm1.listeners.items():
+                listener_addrs = listener.get_addrs()
+                for listener_addr in listener_addrs:
+                    # Create a full multiaddr with peer ID for libp2p connection
+                    peer_id = swarm1.get_peer_id()
+                    full_addr = listener_addr.encapsulate(f"/p2p/{peer_id}")
+
+                    # Test real libp2p connection
+                    try:
+                        peer_info = info_from_p2p_addr(full_addr)
+
+                        # Add the peer info to swarm2's peerstore so it knows where to connect  # noqa: E501
+                        swarm2.peerstore.add_addrs(
+                            peer_info.peer_id, [listener_addr], 10000
+                        )
+
+                        await swarm2.dial_peer(peer_info.peer_id)
+
+                        # Verify connection was established
+                        assert peer_info.peer_id in swarm2.connections, (
+                            f"Connection to {full_addr} should be established"
+                        )
+                        assert swarm2.get_peer_id() in swarm1.connections, (
+                            f"Connection from {full_addr} should be established"
+                        )
+
+                    except Exception as e:
+                        pytest.fail(
+                            f"Failed to establish libp2p connection to {full_addr}: {e}"
+                        )

tests/examples/test_echo_thin_waist.py

@@ -0,0 +1,109 @@
+import contextlib
+import os
+from pathlib import Path
+import subprocess
+import sys
+import time
+
+from multiaddr import Multiaddr
+from multiaddr.protocols import P_IP4, P_IP6, P_P2P, P_TCP
+
+# pytestmark = pytest.mark.timeout(20)  # Temporarily disabled for debugging
+
+# This test is intentionally lightweight and can be marked as 'integration'.
+# It ensures the echo example runs and prints the new Thin Waist lines using
+# Trio primitives.
+
+current_file = Path(__file__)
+project_root = current_file.parent.parent.parent
+EXAMPLES_DIR: Path = project_root / "examples" / "echo"
+
+
+def test_echo_example_starts_and_prints_thin_waist(monkeypatch, tmp_path):
+    """Run echo server and validate printed multiaddr and peer id."""
+    # Run echo example as server
+    cmd = [sys.executable, "-u", str(EXAMPLES_DIR / "echo.py"), "-p", "0"]
+    env = {**os.environ, "PYTHONUNBUFFERED": "1"}
+    proc: subprocess.Popen[str] = subprocess.Popen(
+        cmd,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT,
+        text=True,
+        env=env,
+    )
+
+    if proc.stdout is None:
+        proc.terminate()
+        raise RuntimeError("Process stdout is None")
+    out_stream = proc.stdout
+
+    peer_id: str | None = None
+    printed_multiaddr: str | None = None
+    saw_waiting = False
+
+    start = time.time()
+    timeout_s = 8.0
+    try:
+        while time.time() - start < timeout_s:
+            line = out_stream.readline()
+            if not line:
+                time.sleep(0.05)
+                continue
+            s = line.strip()
+            if s.startswith("I am "):
+                peer_id = s.partition("I am ")[2]
+            if s.startswith("echo-demo -d "):
+                printed_multiaddr = s.partition("echo-demo -d ")[2]
+            if "Waiting for incoming connections..." in s:
+                saw_waiting = True
+                break
+    finally:
+        with contextlib.suppress(ProcessLookupError):
+            proc.terminate()
+        with contextlib.suppress(ProcessLookupError):
+            proc.kill()
+
+    assert peer_id, "Did not capture peer ID line"
+    assert printed_multiaddr, "Did not capture multiaddr line"
+    assert saw_waiting, "Did not capture waiting-for-connections line"
+
+    # Validate multiaddr structure using py-multiaddr protocol methods
+    ma = Multiaddr(printed_multiaddr)  # should parse without error
+
+    # Check that the multiaddr contains the p2p protocol
+    try:
+        peer_id_from_multiaddr = ma.value_for_protocol("p2p")
+        assert peer_id_from_multiaddr is not None, (
+            "Multiaddr missing p2p protocol value"
+        )
+        assert peer_id_from_multiaddr == peer_id, (
+            f"Peer ID mismatch: {peer_id_from_multiaddr} != {peer_id}"
+        )
+    except Exception as e:
+        raise AssertionError(f"Failed to extract p2p protocol value: {e}")
+
+    # Validate the multiaddr structure by checking protocols
+    protocols = ma.protocols()
+
+    # Should have at least IP, TCP, and P2P protocols
+    assert any(p.code == P_IP4 or p.code == P_IP6 for p in protocols), (
+        "Missing IP protocol"
+    )
+    assert any(p.code == P_TCP for p in protocols), "Missing TCP protocol"
+    assert any(p.code == P_P2P for p in protocols), "Missing P2P protocol"
+
+    # Extract the p2p part and validate it matches the captured peer ID
+    p2p_part = Multiaddr(f"/p2p/{peer_id}")
+    try:
+        # Decapsulate the p2p part to get the transport address
+        transport_addr = ma.decapsulate(p2p_part)
+        # Verify the decapsulated address doesn't contain p2p
+        transport_protocols = transport_addr.protocols()
+        assert not any(p.code == P_P2P for p in transport_protocols), (
+            "Decapsulation failed - still contains p2p"
+        )
+        # Verify the original multiaddr can be reconstructed
+        reconstructed = transport_addr.encapsulate(p2p_part)
+        assert str(reconstructed) == str(ma), "Reconstruction failed"
+    except Exception as e:
+        raise AssertionError(f"Multiaddr decapsulation failed: {e}")

tests/utils/test_address_validation.py

@@ -0,0 +1,56 @@
+import os
+
+import pytest
+from multiaddr import Multiaddr
+
+from libp2p.utils.address_validation import (
+    expand_wildcard_address,
+    get_available_interfaces,
+    get_optimal_binding_address,
+)
+
+
+@pytest.mark.parametrize("proto", ["tcp"])
+def test_get_available_interfaces(proto: str) -> None:
+    interfaces = get_available_interfaces(0, protocol=proto)
+    assert len(interfaces) > 0
+    for addr in interfaces:
+        assert isinstance(addr, Multiaddr)
+        assert f"/{proto}/" in str(addr)
+
+
+def test_get_optimal_binding_address() -> None:
+    addr = get_optimal_binding_address(0)
+    assert isinstance(addr, Multiaddr)
+    # At least IPv4 or IPv6 prefix present
+    s = str(addr)
+    assert ("/ip4/" in s) or ("/ip6/" in s)
+
+
+def test_expand_wildcard_address_ipv4() -> None:
+    wildcard = Multiaddr("/ip4/0.0.0.0/tcp/0")
+    expanded = expand_wildcard_address(wildcard)
+    assert len(expanded) > 0
+    for e in expanded:
+        assert isinstance(e, Multiaddr)
+        assert "/tcp/" in str(e)
+
+
+def test_expand_wildcard_address_port_override() -> None:
+    wildcard = Multiaddr("/ip4/0.0.0.0/tcp/7000")
+    overridden = expand_wildcard_address(wildcard, port=9001)
+    assert len(overridden) > 0
+    for e in overridden:
+        assert str(e).endswith("/tcp/9001")
+
+
+@pytest.mark.skipif(
+    os.environ.get("NO_IPV6") == "1",
+    reason="Environment disallows IPv6",
+)
+def test_expand_wildcard_address_ipv6() -> None:
+    wildcard = Multiaddr("/ip6/::/tcp/0")
+    expanded = expand_wildcard_address(wildcard)
+    assert len(expanded) > 0
+    for e in expanded:
+        assert "/ip6/" in str(e)