diff --git a/shadowsocks/tcprelay.py b/shadowsocks/tcprelay.py
index d86c988..729aa04 100644
--- a/shadowsocks/tcprelay.py
+++ b/shadowsocks/tcprelay.py
@@ -94,8 +94,6 @@ BUF_SIZE = 32 * 1024
 
 
 class TCPRelayHandler(object):
-    support_ipv6 = None
-
     def __init__(self, server, fd_to_handlers, loop, local_sock, config,
                  dns_resolver, is_local):
         self._server = server
@@ -103,6 +101,7 @@ class TCPRelayHandler(object):
         self._loop = loop
         self._local_sock = local_sock
         self._remote_sock = None
+        self._remote_sock_v6 = None
         self._remote_udp = False
         self._config = config
         self._dns_resolver = dns_resolver
@@ -194,7 +193,7 @@ class TCPRelayHandler(object):
         if not data or not sock:
             return False
         #logging.debug("_write_to_sock %s %s %s" % (self._remote_sock, sock, self._remote_udp))
-        if self._remote_sock == sock and self._remote_udp:
+        if self._remote_udp and self._remote_sock == sock:
             try:
                 frag = common.ord(data[2])
                 if frag != 0:
@@ -211,11 +210,15 @@ class TCPRelayHandler(object):
                 if addrs:
                     af, socktype, proto, canonname, server_addr = addrs[0]
                     data = data[header_length:]
-                    sock.sendto(data, (server_addr[0], dest_port))
+                    if af == socket.AF_INET6:
+                        self._remote_sock_v6.sendto(data, (server_addr[0], dest_port))
+                    else:
+                        sock.sendto(data, (server_addr[0], dest_port))
 
             except Exception as e:
-                trace = traceback.format_exc()
-                logging.error(trace)
+                #trace = traceback.format_exc()
+                #logging.error(trace)
+                logging.error(e)
             return True
 
         uncomplete = False
@@ -362,18 +365,10 @@ class TCPRelayHandler(object):
                 return True
         return False
 
-    def _is_support_ipv6(self):
-        if TCPRelayHandler.support_ipv6 is None:
-            local = socket.gethostbyaddr(socket.gethostname())
-            TCPRelayHandler.support_ipv6 = self._has_ipv6_addr(local)
-        return TCPRelayHandler.support_ipv6
-
     def _create_remote_socket(self, ip, port):
         if self._remote_udp:
-            if self._is_support_ipv6():
-                addrs = socket.getaddrinfo("::", 0, 0, socket.SOCK_DGRAM, socket.SOL_UDP)
-            else:
-                addrs = socket.getaddrinfo("0.0.0.0", 0, 0, socket.SOCK_DGRAM, socket.SOL_UDP)
+            addrs_v6 = socket.getaddrinfo("::", 0, 0, socket.SOCK_DGRAM, socket.SOL_UDP)
+            addrs = socket.getaddrinfo("0.0.0.0", 0, 0, socket.SOCK_DGRAM, socket.SOL_UDP)
         else:
             addrs = socket.getaddrinfo(ip, port, 0, socket.SOCK_STREAM, socket.SOL_TCP)
         if len(addrs) == 0:
@@ -385,7 +380,15 @@ class TCPRelayHandler(object):
                                 common.to_str(sa[0]))
         remote_sock = socket.socket(af, socktype, proto)
         self._remote_sock = remote_sock
+
         self._fd_to_handlers[remote_sock.fileno()] = self
+
+        if self._remote_udp:
+            af, socktype, proto, canonname, sa = addrs_v6[0]
+            remote_sock_v6 = socket.socket(af, socktype, proto)
+            self._remote_sock_v6 = remote_sock_v6
+            self._fd_to_handlers[remote_sock_v6.fileno()] = self
+
         remote_sock.setblocking(False)
         if self._remote_udp:
             pass
@@ -425,6 +428,9 @@ class TCPRelayHandler(object):
                         if self._remote_udp:
                             self._loop.add(remote_sock,
                                            eventloop.POLL_IN)
+                            if self._remote_sock_v6:
+                                self._loop.add(self._remote_sock_v6,
+                                        eventloop.POLL_IN)
                         else:
                             try:
                                 remote_sock.connect((remote_addr, remote_port))
@@ -482,13 +488,16 @@ class TCPRelayHandler(object):
                 (not is_local and self._stage == STAGE_INIT):
             self._handle_stage_addr(data)
 
-    def _on_remote_read(self):
+    def _on_remote_read(self, is_remote_sock):
         # handle all remote read events
         self._update_activity()
         data = None
         try:
             if self._remote_udp:
-                data, addr = self._remote_sock.recvfrom(BUF_SIZE)
+                if is_remote_sock:
+                    data, addr = self._remote_sock.recvfrom(BUF_SIZE)
+                else:
+                    data, addr = self._remote_sock_v6.recvfrom(BUF_SIZE)
                 port = struct.pack('>H', addr[1])
                 try:
                     ip = socket.inet_aton(addr[0])
@@ -557,13 +566,13 @@ class TCPRelayHandler(object):
             logging.debug('ignore handle_event: destroyed')
             return
         # order is important
-        if sock == self._remote_sock:
+        if sock == self._remote_sock or sock == self._remote_sock_v6:
             if event & eventloop.POLL_ERR:
                 self._on_remote_error()
                 if self._stage == STAGE_DESTROYED:
                     return
             if event & (eventloop.POLL_IN | eventloop.POLL_HUP):
-                self._on_remote_read()
+                self._on_remote_read(sock == self._remote_sock)
                 if self._stage == STAGE_DESTROYED:
                     return
             if event & eventloop.POLL_OUT:
@@ -610,6 +619,12 @@ class TCPRelayHandler(object):
             del self._fd_to_handlers[self._remote_sock.fileno()]
             self._remote_sock.close()
             self._remote_sock = None
+        if self._remote_sock_v6:
+            logging.debug('destroying remote')
+            self._loop.remove(self._remote_sock_v6)
+            del self._fd_to_handlers[self._remote_sock_v6.fileno()]
+            self._remote_sock_v6.close()
+            self._remote_sock_v6 = None
         if self._local_sock:
             logging.debug('destroying local')
             self._loop.remove(self._local_sock)