diff --git a/include/Vutils.h b/include/Vutils.h
index 8f144b6..c91a89a 100644
--- a/include/Vutils.h
+++ b/include/Vutils.h
@@ -1271,6 +1271,13 @@ class Socket : public LastError
   typedef int flags_t;
   typedef int shutdowns_t;
 
+  enum class side_type : uint
+  {
+    SERVER,
+    CLIENT,
+    UNDEFINED,
+  };
+
   struct Handle
   {
     SOCKET s;
@@ -1305,6 +1312,7 @@ class Socket : public LastError
   bool  operator!=(const Socket& right);
   const Socket& operator=(const Socket& right);
 
+  side_type vuapi side() const;
   const SOCKET& vuapi handle() const;
   const address_family_t vuapi af() const;
   const type_t vuapi type() const;
@@ -1357,6 +1365,7 @@ class Socket : public LastError
   std::string vuapi get_host_address(const std::string& name) const;
 
 private:
+  side_type m_side;
   type_t m_type;
   WSADATA m_wsa_data;
   address_family_t m_af;
@@ -1382,12 +1391,6 @@ class AsyncSocket : public LastError
     UNDEFINED,
   };
 
-  enum class side_type : uint
-  {
-    SERVER,
-    CLIENT,
-  };
-
   AsyncSocket(
     const vu::Socket::address_family_t af = AF_INET,
     const vu::Socket::type_t type = SOCK_STREAM,
@@ -1396,8 +1399,7 @@ class AsyncSocket : public LastError
   );
   virtual ~AsyncSocket();
 
-  side_type vuapi side() const;
-
+  Socket::side_type vuapi side() const;
   bool vuapi available() const;
   bool vuapi running() const;
 
@@ -1453,9 +1455,7 @@ class AsyncSocket : public LastError
   HANDLE m_thread;
   std::atomic<bool> m_running;
 
-  side_type  m_side;
   vu::Socket m_socket;
-
   DWORD  m_n_events;
   SOCKET m_connections[WSA_MAXIMUM_WAIT_EVENTS];
   WSAEVENT m_events[WSA_MAXIMUM_WAIT_EVENTS];
diff --git a/src/details/asyncsocket.cpp b/src/details/asyncsocket.cpp
index d6b2afd..c8704f8 100644
--- a/src/details/asyncsocket.cpp
+++ b/src/details/asyncsocket.cpp
@@ -21,8 +21,6 @@ AsyncSocket::AsyncSocket(
   const vu::Socket::Options* options
 ) : m_socket(af, type, proto, options), m_thread(INVALID_HANDLE_VALUE), LastError()
 {
-  UNREFERENCED_PARAMETER(m_side);
-
   this->initialze();
 
   for (uint i = 0; i < function::UNDEFINED; i++)
@@ -45,9 +43,10 @@ void vuapi AsyncSocket::initialze()
   m_running = false;
 }
 
-AsyncSocket::side_type vuapi AsyncSocket::side() const
+
+Socket::side_type vuapi AsyncSocket::side() const
 {
-  return m_side;
+  return m_socket.side();
 }
 
 bool vuapi AsyncSocket::available() const
@@ -68,13 +67,7 @@ VUResult vuapi AsyncSocket::bind(const Endpoint& endpoint)
 VUResult vuapi AsyncSocket::bind(const std::string& address, const ushort port)
 {
   auto result = m_socket.bind(address, port);
-  if (result == VU_OK)
-  {
-    m_side = side_type::SERVER;
-  }
-
   this->set_last_error_code(m_socket.get_last_error_code());
-
   return result;
 }
 
@@ -144,7 +137,6 @@ VUResult vuapi AsyncSocket::connect(const Endpoint& endpoint)
   if (result == VU_OK)
   {
     m_last_error_code = ERROR_SUCCESS;
-    m_side = side_type::CLIENT;
     m_connections[m_n_events] = m_socket.handle();
     m_events[m_n_events] = event;
     m_n_events++;
@@ -177,7 +169,7 @@ void vuapi AsyncSocket::get_connections(std::set<SOCKET>& connections)
       continue;
     }
 
-    if (m_side == side_type::SERVER && socket == m_socket.handle()) // ignore server socket handle
+    if (m_socket.side() == Socket::side_type::SERVER && socket == m_socket.handle()) // ignore server socket handle
     {
       continue;
     }
diff --git a/src/details/socket.cpp b/src/details/socket.cpp
index 8b196e7..5e602c2 100644
--- a/src/details/socket.cpp
+++ b/src/details/socket.cpp
@@ -104,7 +104,8 @@ Socket::Socket(
   const type_t type,
   const protocol_t proto,
   const Options* options
-) : LastError(), m_af(af), m_type(type), m_proto(proto), m_attached(false)
+) : LastError(), m_af(af), m_type(type), m_proto(proto)
+  , m_attached(false), m_side(Socket::side_type::UNDEFINED)
 {
   ZeroMemory(&m_wsa_data, sizeof(m_wsa_data));
   if (WSAStartup(MAKEWORD(2, 2), &m_wsa_data) == INVALID_SOCKET)
@@ -141,11 +142,14 @@ Socket::~Socket()
     return; // ignore if the connection is attached from outside
   }
 
-  if (::closesocket(m_socket) == INVALID_SOCKET)
+  if (this->available())
   {
-    assert("close socket failed.");
-    m_last_error_code = GetLastError();
-    m_socket = INVALID_SOCKET;
+    if (::closesocket(m_socket) == INVALID_SOCKET)
+    {
+      assert("close socket failed.");
+      m_last_error_code = GetLastError();
+      m_socket = INVALID_SOCKET;
+    }
   }
 
   if (WSACleanup() == INVALID_SOCKET)
@@ -183,6 +187,11 @@ const vu::Socket& Socket::operator=(const Socket& right)
   return *this;
 }
 
+Socket::side_type vuapi Socket::side() const
+{
+  return m_side;
+}
+
 bool vuapi Socket::valid(const SOCKET& socket) const
 {
   return !(socket == 0 || socket == INVALID_SOCKET);
@@ -330,6 +339,8 @@ VUResult vuapi Socket::bind(const std::string& address, const ushort port)
     return 3;
   }
 
+  m_side = side_type::SERVER;
+
   return VU_OK;
 }
 
@@ -393,13 +404,16 @@ VUResult vuapi Socket::connect(const Endpoint& endpoint)
   m_sai.sin_addr.S_un.S_addr = inet_addr(ip.c_str());
   m_sai.sin_port = htons(endpoint.m_port);
 
+  VUResult result = VU_OK;
+
   if (::connect(m_socket, (const struct sockaddr*)&m_sai, sizeof(m_sai)) == SOCKET_ERROR)
   {
-    m_last_error_code = GetLastError();
-    return m_last_error_code == WSAEWOULDBLOCK ? VU_OK : 2;
+    result = GetLastError() == WSAEWOULDBLOCK ? VU_OK : 2; // ignore 'A non-blocking socket operation could not be completed immediately.'
   }
 
-  return VU_OK;
+  m_side = side_type::CLIENT;
+
+  return result;
 }
 
 IResult vuapi Socket::send(const char* ptr_data, int size, const flags_t flags)