test: use dynamic port allocation to avoid test conflicts

diff --git a/test/functional/feature_anchors.py b/test/functional/feature_anchors.py
index d3d24f46..e82f28f4 100755
--- a/test/functional/feature_anchors.py
+++ b/test/functional/feature_anchors.py
@@ -10,7 +10,7 @@ from test_framework.p2p import P2PInterface, P2P_SERVICES
 from test_framework.socks5 import Socks5Configuration, Socks5Server
 from test_framework.messages import CAddress, hash256
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import check_node_connections, assert_equal, p2p_port
+from test_framework.util import check_node_connections, assert_equal
 
 INBOUND_CONNECTIONS = 5
 BLOCK_RELAY_CONNECTIONS = 2
@@ -92,7 +92,9 @@ class AnchorsTest(BitcoinTestFramework):
         onion_conf = Socks5Configuration()
         onion_conf.auth = True
         onion_conf.unauth = True
-        onion_conf.addr = ('127.0.0.1', p2p_port(self.num_nodes))
+        # Use port=0 for dynamic allocation to avoid conflicts with concurrent
+        # tests or ports in TIME_WAIT state from previous test runs.
+        onion_conf.addr = ('127.0.0.1', 0)
         onion_conf.keep_alive = True
         onion_proxy = Socks5Server(onion_conf)
         onion_proxy.start()
diff --git a/test/functional/feature_proxy.py b/test/functional/feature_proxy.py
index e95d5ed4..fa4e966e 100755
--- a/test/functional/feature_proxy.py
+++ b/test/functional/feature_proxy.py
@@ -46,10 +46,7 @@ import tempfile
 
 from test_framework.socks5 import Socks5Configuration, Socks5Command, Socks5Server, AddressType
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import (
-    assert_equal,
-    p2p_port,
-)
+from test_framework.util import assert_equal
 from test_framework.netutil import test_ipv6_local, test_unix_socket
 
 # Networks returned by RPC getpeerinfo.
@@ -74,22 +71,24 @@ class ProxyTest(BitcoinTestFramework):
     def setup_nodes(self):
         self.have_ipv6 = test_ipv6_local()
         self.have_unix_sockets = test_unix_socket()
-        # Create two proxies on different ports
+        # Create two proxies on different ports.
+        # Use port=0 to let the OS assign available ports, avoiding
+        # "address already in use" errors from concurrent tests.
         # ... one unauthenticated
         self.conf1 = Socks5Configuration()
-        self.conf1.addr = ('127.0.0.1', p2p_port(self.num_nodes))
+        self.conf1.addr = ('127.0.0.1', 0)
         self.conf1.unauth = True
         self.conf1.auth = False
         # ... one supporting authenticated and unauthenticated (Tor)
         self.conf2 = Socks5Configuration()
-        self.conf2.addr = ('127.0.0.1', p2p_port(self.num_nodes + 1))
+        self.conf2.addr = ('127.0.0.1', 0)
         self.conf2.unauth = True
         self.conf2.auth = True
         if self.have_ipv6:
             # ... one on IPv6 with similar configuration
             self.conf3 = Socks5Configuration()
             self.conf3.af = socket.AF_INET6
-            self.conf3.addr = ('::1', p2p_port(self.num_nodes + 2))
+            self.conf3.addr = ('::1', 0)
             self.conf3.unauth = True
             self.conf3.auth = True
         else:
diff --git a/test/functional/test_framework/p2p.py b/test/functional/test_framework/p2p.py
index 346a7c65..986eaf1e 100755
--- a/test/functional/test_framework/p2p.py
+++ b/test/functional/test_framework/p2p.py
@@ -787,13 +787,14 @@ class NetworkThread(threading.Thread):
                 cls.protos[(addr, port)] = None
             return response
 
-        if (addr, port) not in cls.listeners:
+        if port == 0 or (addr, port) not in cls.listeners:
             # When creating a listener on a given (addr, port) we only need to
             # do it once. If we want different behaviors for different
             # connections, we can accomplish this by providing different
             # `proto` functions
 
             listener = await cls.network_event_loop.create_server(peer_protocol, addr, port)
+            port = listener.sockets[0].getsockname()[1]
             logger.debug("Listening server on %s:%d should be started" % (addr, port))
             cls.listeners[(addr, port)] = listener
 
diff --git a/test/functional/test_framework/socks5.py b/test/functional/test_framework/socks5.py
index 3fd4d5c8..711734cf 100644
--- a/test/functional/test_framework/socks5.py
+++ b/test/functional/test_framework/socks5.py
@@ -203,6 +203,9 @@ class Socks5Server():
         self.s = socket.socket(conf.af)
         self.s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
         self.s.bind(conf.addr)
+        # When port=0, the OS assigns an available port. Update conf.addr
+        # to reflect the actual bound address so callers can use it.
+        self.conf.addr = self.s.getsockname()
         self.s.listen(5)
         self.running = False
         self.thread = None