diff --git a/tests/stun_server.py b/tests/stun_server.py
index 043bace..e178c34 100644
--- a/tests/stun_server.py
+++ b/tests/stun_server.py
@@ -2,11 +2,13 @@
 """
 Minimal STUN server implementing RFC 5389 Binding Request/Response.
 
-Other STUN message types (TURN Allocate, Send/Data/Channel, etc.) are
-silently ignored.  Message integrity (HMAC-SHA1) is not implemented.
+Supports both IPv4 and IPv6.  Other STUN message types (TURN Allocate,
+Send/Data/Channel, etc.) are silently ignored.  Message integrity
+(HMAC-SHA1) is not implemented.
 """
 
 import argparse
+import select
 import socket
 import struct
 import sys
@@ -16,37 +18,62 @@ MSG_BINDING_REQUEST     = 0x0001
 MSG_BINDING_SUCCESS     = 0x0101
 ATTR_XOR_MAPPED_ADDRESS = 0x0020
 
-def run(host, port):
-    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
-    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
-    sock.bind((host, port))
-    print("STUN server listening on %s:%d" % (host, port), flush=True)
+def build_xor_mapped_address(addr, port, transaction_id):
+    xport = port ^ (STUN_MAGIC_COOKIE >> 16)
+    if ':' in addr:
+        # IPv6: XOR 16-byte address with magic_cookie || transaction_id
+        raw = socket.inet_pton(socket.AF_INET6, addr)
+        xor_key = struct.pack('!I', STUN_MAGIC_COOKIE) + transaction_id
+        xraw = bytes(a ^ b for a, b in zip(raw, xor_key))
+        attr_body = struct.pack('!BBH', 0x00, 0x02, xport) + xraw
+    else:
+        # IPv4: XOR 4-byte address with magic cookie
+        xip = struct.unpack('!I', socket.inet_aton(addr))[0] ^ STUN_MAGIC_COOKIE
+        attr_body = struct.pack('!BBH I', 0x00, 0x01, xport, xip)
+    return struct.pack('!HH', ATTR_XOR_MAPPED_ADDRESS, len(attr_body)) + attr_body
+
+def handle_packet(sock, data, addr):
+    if len(data) < 20:
+        print("Dropped runt packet (%d bytes) from %s:%d" % (len(data), addr[0], addr[1]), flush=True)
+        return
+    msg_type, _msg_len, magic = struct.unpack_from('!HHI', data)
+    if magic != STUN_MAGIC_COOKIE:
+        print("Dropped packet from %s:%d: bad magic 0x%08x" % (addr[0], addr[1], magic), flush=True)
+        return
+    if msg_type != MSG_BINDING_REQUEST:
+        print("Dropped packet from %s:%d: unexpected message type 0x%04x" % (addr[0], addr[1], msg_type), flush=True)
+        return
+    print("Binding request from %s:%d" % (addr[0], addr[1]), flush=True)
+    transaction_id = data[8:20]
+    attr = build_xor_mapped_address(addr[0], addr[1], transaction_id)
+    response = struct.pack('!HHI', MSG_BINDING_SUCCESS, len(attr), STUN_MAGIC_COOKIE) \
+               + transaction_id + attr
+    sock.sendto(response, addr)
+
+def run(host4, host6, port):
+    socks = []
+
+    if host4:
+        s4 = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        s4.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        s4.bind((host4, port))
+        print("STUN server listening on %s:%d" % (host4, port), flush=True)
+        socks.append(s4)
+
+    if host6:
+        s6 = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
+        s6.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        s6.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 1)
+        s6.bind((host6, port))
+        print("STUN server listening on [%s]:%d" % (host6, port), flush=True)
+        socks.append(s6)
 
     while True:
         try:
-            data, addr = sock.recvfrom(2048)
-            if len(data) < 20:
-                print("Dropped runt packet (%d bytes) from %s:%d" % (len(data), addr[0], addr[1]), flush=True)
-                continue
-            msg_type, _msg_len, magic = struct.unpack_from('!HHI', data)
-            if magic != STUN_MAGIC_COOKIE:
-                print("Dropped packet from %s:%d: bad magic 0x%08x" % (addr[0], addr[1], magic), flush=True)
-                continue
-            if msg_type != MSG_BINDING_REQUEST:
-                print("Dropped packet from %s:%d: unexpected message type 0x%04x" % (addr[0], addr[1], msg_type), flush=True)
-                continue
-            print("Binding request from %s:%d" % (addr[0], addr[1]), flush=True)
-            transaction_id = data[8:20]
-
-            # XOR-MAPPED-ADDRESS (IPv4)
-            xport = addr[1] ^ (STUN_MAGIC_COOKIE >> 16)
-            xip   = struct.unpack('!I', socket.inet_aton(addr[0]))[0] ^ STUN_MAGIC_COOKIE
-            attr_body = struct.pack('!BBH I', 0x00, 0x01, xport, xip)
-            attr = struct.pack('!HH', ATTR_XOR_MAPPED_ADDRESS, len(attr_body)) + attr_body
-
-            response = struct.pack('!HHI', MSG_BINDING_SUCCESS, len(attr), STUN_MAGIC_COOKIE) \
-                       + transaction_id + attr
-            sock.sendto(response, addr)
+            readable, _, _ = select.select(socks, [], [])
+            for sock in readable:
+                data, addr = sock.recvfrom(2048)
+                handle_packet(sock, data, addr)
         except KeyboardInterrupt:
             break
         except Exception as e:
@@ -56,8 +83,10 @@ if __name__ == '__main__':
     parser = argparse.ArgumentParser(
         description='Minimal STUN server (RFC 5389 Binding Request only; no message integrity)')
     parser.add_argument('--host', default='0.0.0.0',
-                        help='IP address to bind (default: 0.0.0.0)')
+                        help='IPv4 address to bind (default: 0.0.0.0)')
+    parser.add_argument('--host6', default=None,
+                        help='IPv6 address to bind (optional)')
     parser.add_argument('--port', type=int, default=3478,
                         help='UDP port to listen on (default: 3478)')
     args = parser.parse_args()
-    run(args.host, args.port)
+    run(args.host, args.host6, args.port)