diff --git a/client/IOCPClient.cpp b/client/IOCPClient.cpp
index 30459c6..9441798 100644
--- a/client/IOCPClient.cpp
+++ b/client/IOCPClient.cpp
@@ -373,6 +373,7 @@ bool IOCPClient::ProcessRecvData(CBuffer *m_CompressedBuffer, char *szBuffer, in
     int iReceivedLength = ReceiveData(szBuffer, len, flag);
     if (iReceivedLength <= 0) {
         int a = WSAGetLastError();
+        Mprintf("[recv] return %d, GetLastError= %d. \n", iReceivedLength, a);
         Disconnect(); //½ÓÊÕ´íÎó´¦Àí
         m_CompressedBuffer->ClearBuffer();
         if (m_exit_while_disconnect)
diff --git a/client/ScreenManager.cpp b/client/ScreenManager.cpp
index c4ac9a4..321fc56 100644
--- a/client/ScreenManager.cpp
+++ b/client/ScreenManager.cpp
@@ -262,7 +262,7 @@ VOID CScreenManager::SendBitMapInfo()
     //ÕâÀｫbmpλͼ½á¹¹·¢ËͳöÈ¥
     memcpy(szBuffer + 1, m_ScreenSpyObject->GetBIData(), ulLength - 1);
     HttpMask mask(DEFAULT_HOST, m_ClientObject->GetClientIPHeader());
-    m_ClientObject->Send2Server((char*)szBuffer, ulLength, &mask);
+    m_ClientObject->Send2Server((char*)szBuffer, ulLength, 0);
     VirtualFree(szBuffer, 0, MEM_RELEASE);
 }
 
diff --git a/common/locker.h b/common/locker.h
index 3caffcb..79f6515 100644
--- a/common/locker.h
+++ b/common/locker.h
@@ -87,6 +87,23 @@ public:
     }
 };
 
+class CAutoCLock
+{
+private:
+	CLock& m_cs;
+
+public:
+    CAutoCLock(CLock& cs) : m_cs(cs)
+	{
+        m_cs.Lock();
+	}
+
+	~CAutoCLock()
+	{
+        m_cs.Unlock();
+	}
+};
+
 // 智能计时器，计算函数的耗时
 class auto_tick
 {
diff --git a/server/2015Remote/IOCPServer.cpp b/server/2015Remote/IOCPServer.cpp
index d7e6891..aea115a 100644
--- a/server/2015Remote/IOCPServer.cpp
+++ b/server/2015Remote/IOCPServer.cpp
@@ -593,6 +593,7 @@ BOOL IOCPServer::OnClientPreSending(CONTEXT_OBJECT* ContextObject, PBYTE szBuffe
 
 BOOL IOCPServer::OnClientPostSending(CONTEXT_OBJECT* ContextObject,ULONG ulCompletedLength)
 {
+    CAutoCLock L(ContextObject->SendLock);
     try {
         DWORD ulFlags = MSG_PARTIAL;
 
@@ -609,10 +610,12 @@ BOOL IOCPServer::OnClientPostSending(CONTEXT_OBJECT* ContextObject,ULONG ulCompl
                               NULL, ulFlags,&OverlappedPlus->m_ol, NULL);
             if ( iOk == SOCKET_ERROR && WSAGetLastError() != WSA_IO_PENDING ) {
                 int a = GetLastError();
-                Mprintf("!!! OnClientPostSending ͶµÝÏûϢʧ°Ü\n");
+                Mprintf("!!! OnClientPostSending ͶµÝÏûϢʧ°Ü: %d\n", a);
                 RemoveStaleContext(ContextObject);
                 SAFE_DELETE(OverlappedPlus);
+                return FALSE;
             }
+            return TRUE;
         }
     } catch(...) {
         Mprintf("[ERROR] OnClientPostSending catch an error \n");
diff --git a/server/2015Remote/Server.h b/server/2015Remote/Server.h
index 8394ebd..954923c 100644
--- a/server/2015Remote/Server.h
+++ b/server/2015Remote/Server.h
@@ -374,6 +374,7 @@ public:
     Server*				server;						// ËùÊô·þÎñ¶Ë
     ikcpcb*				kcp = nullptr;				// ÐÂÔö£¬Ö¸ÏòKCP»á»°
     std::string			GroupName;					// ·Ö×éÃû³Æ
+    CLock               SendLock;                   // fix #214
 
     std::string GetProtocol() const override
     {
@@ -411,8 +412,10 @@ public:
     }
     BOOL Send2Client(PBYTE szBuffer, ULONG ulOriginalLength) override
     {
-        if (server)
+        if (server) {
+            CAutoCLock L(SendLock);
             return server->Send2Client(this, szBuffer, ulOriginalLength);
+        }
         return FALSE;
     }
     VOID SetClientInfo(const CString(&s)[ONLINELIST_MAX], const std::vector<std::string>& a = {})