CE_Service_Handler和ACE_Svc_Handler是類似的，不同的是使用在proactor中。
ACE_Service_Handler類從代碼的接口中直接可以看到很多相關的回調，例如
handle_write_stream ，那麼它們是什麼時候被調的呢？看下代碼：
00369 void
00370 ACE_POSIX_Asynch_Write_Stream_Result::complete (size_t bytes_transferred,
00371 int success,
00372 const void *completion_key,
00373 u_long error)
00374 {
00375 // Get all the data copied.
00376 this->bytes_transferred_ = bytes_transferred;
00377 this->success_ = success;
00378 this->completion_key_ = completion_key;
00379 this->error_ = error;
00380
00381 // <errno> is available in the aiocb.
00382 ACE_UNUSED_ARG (error);
00383
00384 // Appropriately move the pointers in the message block.
00385 this->message_block_.rd_ptr (bytes_transferred);
00386
00387 // Create the interface result class.
00388 ACE_Asynch_Write_Stream::Result result (this);
00389
00390 // Call the application handler.
00391 ACE_Handler *handler = this->handler_proxy_.get ()->handler ();
00392 if (handler != 0)
00393 handler->handle_write_stream (result);
00394 在上述的393行，而這裡的complete的調用位置是：
00556 void
00557 ACE_POSIX_Proactor::application_specific_code (ACE_POSIX_Asynch_Result *asynch_result,
00558 size_t bytes_transferred,
00559 const void */* completion_key*/,
00560 u_long error)
00561 {
00562 ACE_SEH_TRY
00563 {
00564 // Call completion hook
00565 asynch_result->complete (bytes_transferred,
00566 error ? 0 : 1,
00567 0, // No completion key.
00568 error);
00569 }
00570 ACE_SEH_FINALLY
00571 {
00572 // This is crucial to prevent memory leaks
00573 delete asynch_result;
00574 }
00575 }
00576 但是看過這個函數的調用之後，會發現無論是在windows還是posix的實作中，這個函數都再handel_events中被調用。而且這裡在ACE_Proactor中，run_event_loop都是空實作，其handle_events是在proactor_run_event_loop函數中被調用的，這點尤其需要注意。
另外的一個問題是，ACE_Asynch_Connector/Acceptor《handler》這些實際處理事件的模闆類，是如何将handler和proactor聯系起來的？
1.先看看ACE_Proactor是何時産生的。
通過堆棧檢視到，ACE_Asynch_Connector的open函數會調用其私有成員變量ACE_Asynch_Connect類型的asynch_connect_的open函數，在這個函數中會調用get_proactor接口為user擷取一個proactor，ACE_Proactor的第一個執行個體就在這裡執行個體化了，至于為什麼ACE_Proactor的執行個體會是ACE_POSIX_AIOCB_Proactor，和這裡的ACE_REGISTER_FRAMEWORK_COMPONENT顯然脫不了幹系。
00360 ACE_Proactor *
00361 ACE_Proactor::instance (size_t /* threads */)
00362 {
00363 ACE_TRACE ("ACE_Proactor::instance");
00364
00365 if (ACE_Proactor::proactor_ == 0)
00366 {
00367 // Perform Double-Checked Locking Optimization.
00368 ACE_MT (ACE_GUARD_RETURN (ACE_Recursive_Thread_Mutex, ace_mon,
00369 *ACE_Static_Object_Lock::instance (),
00370 0));
00371
00372 if (ACE_Proactor::proactor_ == 0)
00373 {
00374 ACE_NEW_RETURN (ACE_Proactor::proactor_,
00375 ACE_Proactor,
00376 0);
00377
00378 ACE_Proactor::delete_proactor_ = 1;
00379 ACE_REGISTER_FRAMEWORK_COMPONENT(ACE_Proactor, ACE_Proactor::proactor_);
00380 }
00381 }
00382 return ACE_Proactor::proactor_; 00077 template <class HANDLER> void
00078 ACE_Asynch_Connector<HANDLER>::handle_connect (const ACE_Asynch_Connect::Result &result)
00079 {
00080 // Variable for error tracking
00081 int error = 0;
00082
00083 // If the asynchronous connect fails.
00084 if (!result.success () ||
00085 result.connect_handle () == ACE_INVALID_HANDLE)
00086 {
00087 error = 1;
00088 }
00089
00090 if (result.error () != 0)
00091 {
00092 error = 1;
00093 }
00094
00095 // set blocking mode
00096 if (!error &&
00097 ACE::clr_flags
00098 (result.connect_handle (), ACE_NONBLOCK) != 0)
00099 {
00100 error = 1;
00101 ACE_ERROR ((LM_ERROR,
00102 ACE_LIB_TEXT ("%p\n"),
00103 ACE_LIB_TEXT ("ACE_Asynch_Connector::handle_connect : Set blocking mode")));
00104 }
00105
00106 // Parse the addresses.
00107 ACE_INET_Addr local_address;
00108 ACE_INET_Addr remote_address;
00109 if (!error &&
00110 (this->validate_new_connection_ || this->pass_addresses_))
00111 this->parse_address (result,
00112 remote_address,
00113 local_address);
00114
00115 // Call validate_connection even if there was an error - it's the only
00116 // way the application can learn the connect disposition.
00117 if (this->validate_new_connection_ &&
00118 this->validate_connection (result, remote_address, local_address) == -1)
00119 {
00120 error = 1;
00121 }
00122
00123 HANDLER *new_handler = 0;
00124 if (!error)
00125 {
00126 // The Template method
00127 new_handler = this->make_handler ();
00128 if (new_handler == 0)
00129 {
00130 error = 1;
00131 ACE_ERROR ((LM_ERROR,
00132 ACE_LIB_TEXT ("%p\n"),
00133 ACE_LIB_TEXT ("ACE_Asynch_Connector::handle_connect : Making of new handler failed")));
00134 }
00135 }
00136
00137 // If no errors
00138 if (!error)
00139 {
00140 // Update the Proactor.
00141 new_handler->proactor (this->proactor ());
00142
00143 // Pass the addresses
00144 if (this->pass_addresses_)
00145 new_handler->addresses (remote_address,
00146 local_address);
00147
00148 // Pass the ACT
00149 if (result.act () != 0)
00150 new_handler->act (result.act ());
00151
00152 // Set up the handler's new handle value
00153 new_handler->handle (result.connect_handle ());
00154
00155 ACE_Message_Block mb;
00156
00157 // Initiate the handler with empty message block;
00158 new_handler->open (result.connect_handle (), mb);
00159 }
00160
00161 // On failure, no choice but to close the socket
00162 if (error &&
00163 result.connect_handle() != ACE_INVALID_HANDLE)
00164 ACE_OS::closesocket (result.connect_handle ());
00165 - 建立連接配接，擷取handle，這是Connector的handle_connect完成的
- 将handle加入proactor的檢測隊列，并将ACE_Message_Block和其綁定，用于資料處理，這是由ACE_Aysnch_Read/Write_Stream的open及相關接口完成（需要我們負責手動去完成他們的綁定即調open接口(在handler的open接口中)）
- 擷取handle上處理完成，并将最終結果的ACE_Message_Block通知并進行通知處理，則是由Handler中的virtual void handle_read_stream 等回調來完成。（負責實作回調）
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