diff --git a/shadowsocks/asyncdns.py b/shadowsocks/asyncdns.py
index e64895c..d958752 100644
--- a/shadowsocks/asyncdns.py
+++ b/shadowsocks/asyncdns.py
@@ -83,9 +83,11 @@ def detect_ipv6_supprot():
         s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
         try:
             s.connect(('ipv6.google.com', 0))
+            print('IPv6 support')
             return True
         except:
             pass
+    print('IPv6 not support')
     return False
 
 IPV6_CONNECTION_SUPPORT = detect_ipv6_supprot()
@@ -356,19 +358,34 @@ class DNSResolver(object):
                         answer[2] == QCLASS_IN:
                     ip = answer[0]
                     break
-            if not ip and self._hostname_status.get(hostname, STATUS_IPV4) \
-                    == STATUS_IPV6:
-                self._hostname_status[hostname] = STATUS_IPV4
-                self._send_req(hostname, QTYPE_A)
+            if IPV6_CONNECTION_SUPPORT:
+                if not ip and self._hostname_status.get(hostname, STATUS_IPV4) \
+                        == STATUS_IPV6:
+                    self._hostname_status[hostname] = STATUS_IPV4
+                    self._send_req(hostname, QTYPE_A)
+                else:
+                    if ip:
+                        self._cache[hostname] = ip
+                        self._call_callback(hostname, ip)
+                    elif self._hostname_status.get(hostname, None) == STATUS_IPV4:
+                        for question in response.questions:
+                            if question[1] == QTYPE_A:
+                                self._call_callback(hostname, None)
+                                break
             else:
-                if ip:
-                    self._cache[hostname] = ip
-                    self._call_callback(hostname, ip)
-                elif self._hostname_status.get(hostname, None) == STATUS_IPV4:
-                    for question in response.questions:
-                        if question[1] == QTYPE_A:
-                            self._call_callback(hostname, None)
-                            break
+                if not ip and self._hostname_status.get(hostname, STATUS_IPV6) \
+                        == STATUS_IPV4:
+                    self._hostname_status[hostname] = STATUS_IPV6
+                    self._send_req(hostname, QTYPE_AAAA)
+                else:
+                    if ip:
+                        self._cache[hostname] = ip
+                        self._call_callback(hostname, ip)
+                    elif self._hostname_status.get(hostname, None) == STATUS_IPV6:
+                        for question in response.questions:
+                            if question[1] == QTYPE_AAAA:
+                                self._call_callback(hostname, None)
+                                break
 
     def handle_event(self, sock, fd, event):
         if sock != self._sock:
diff --git a/shadowsocks/obfsplugin/http_simple.py b/shadowsocks/obfsplugin/http_simple.py
index efd7f2a..8144aa8 100644
--- a/shadowsocks/obfsplugin/http_simple.py
+++ b/shadowsocks/obfsplugin/http_simple.py
@@ -192,6 +192,9 @@ class http2_simple(plain.plain):
             return buf
         self.send_buffer += buf
         if not self.has_sent_header:
+            port = b''
+            if self.server_info.port != 80:
+                port = b':' + common.to_bytes(str(self.server_info.port))
             self.has_sent_header = True
             http_head = b"GET / HTTP/1.1\r\n"
             http_head += b"Host: " + (self.server_info.param or self.server_info.host) + port + b"\r\n"
diff --git a/shadowsocks/tcprelay.py b/shadowsocks/tcprelay.py
index cce6df5..e1ea954 100644
--- a/shadowsocks/tcprelay.py
+++ b/shadowsocks/tcprelay.py
@@ -523,8 +523,8 @@ class TCPRelayHandler(object):
                             try:
                                 remote_sock.connect((remote_addr, remote_port))
                             except (OSError, IOError) as e:
-                                if eventloop.errno_from_exception(e) == \
-                                        errno.EINPROGRESS:
+                                if eventloop.errno_from_exception(e) in (errno.EINPROGRESS,
+                                        errno.EWOULDBLOCK):
                                     pass # always goto here
                                 else:
                                     raise e
diff --git a/shadowsocks/udprelay.py b/shadowsocks/udprelay.py
index b4fcae3..12676f7 100644
--- a/shadowsocks/udprelay.py
+++ b/shadowsocks/udprelay.py
@@ -207,7 +207,7 @@ class RecvQueue(object):
     def set_end(self, end_id):
         if end_id > self.end_id:
             eid = self.end_id
-            while eid < pack_id:
+            while eid < end_id:
                 self.miss_queue.add(eid)
                 eid += 1
             self.end_id = end_id
@@ -623,6 +623,7 @@ class TCPRelayHandler(object):
             for pid in missing:
                 data += struct.pack(">H", pid)
             rsp_data = self._pack_post_data(CMD_SYN_STATUS, pack_id, data)
+            addr = self.get_local_address()
             self._write_to_sock(rsp_data, self._local_sock, addr)
 
     def handle_stream_sync_status(self, addr, cmd, request_id, pack_id, max_send_id, data):