fix: correct listening address variable in echo example and streamline address printing

examples/echo/echo.py

@@ -47,7 +47,7 @@ async def run(port: int, destination: str, seed: int | None = None) -> None:
         secret = secrets.token_bytes(32)
 
     host = new_host(key_pair=create_new_key_pair(secret))
-    async with host.run(listen_addrs=listen_addrs), trio.open_nursery() as nursery:
+    async with host.run(listen_addr=listen_addr), trio.open_nursery() as nursery:
         # Start the peer-store cleanup task
         nursery.start_soon(host.get_peerstore().start_cleanup_task, 60)
 
@@ -59,8 +59,7 @@ async def run(port: int, destination: str, seed: int | None = None) -> None:
             # Print all listen addresses with peer ID (JS parity)
             print("Listener ready, listening on:")
             peer_id = host.get_id().to_string()
-            for addr in listen_addrs:
-                print(f"{addr}/p2p/{peer_id}")
+            print(f"{listen_addr}/p2p/{peer_id}")
 
             print(
                 "\nRun this from the same folder in another console:\n\n"

libp2p/utils/address_validation.py

@@ -62,16 +62,18 @@ def get_available_interfaces(port: int, protocol: str = "tcp") -> 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}"))
 
+    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}"))
+
     # IPv6 enumeration (optional: only include if we have at least one global or
     # loopback)
-    for ip in _safe_get_network_addrs(6):
-        # Avoid returning unusable wildcard expansions if the environment does not
-        # support IPv6
-        addrs.append(Multiaddr(f"/ip6/{ip}/{protocol}/{port}"))
     # Optionally ensure IPv6 loopback when any IPv6 present but loopback missing
     if seen_v6 and "::1" not in seen_v6:
         addrs.append(Multiaddr(f"/ip6/::1/{protocol}/{port}"))