Windows进程间通信（下）

Posted 2020-06-08

六、动态数据交换（Dynamic Data Exchange）

动态数据交换(DDE)是使用共享内存在应用程序之间进行数据交换的一种进程间通信形式。应用程序可以使用DDE进行一次性数据传输，也可以当出现新数据时，通过发送更新值在应用程序间动态交换数据。
DDE 和剪贴板一样既支持标准数据格式(如文本、位图等)，又可以支持自己定义的数据格式。但它们的数据传输机制却不同，一个明显区别是剪贴板操作几乎总是用作对用户指定操作的一次性应答－如从菜单中选择Paste命令。尽管DDE也可以由用户启动，但它继续发挥作用一般不必用户进一步干预。DDE有 三种数据交换方式：
(1) 冷链：数据交换是一次性数据传输，与剪贴板相同。
(2) 温链：当数据交换时服务器通知客户，然后客户必须请求新的数据。
(3) 热链：当数据交换时服务器自动给客户发送数据。
DDE交换可以发生在单机或网络中不同计算机的应用程序之间。开发者还可以定义定制的DDE数据格式进行应用程序之间特别目的IPC，它们有更紧密耦合的通信要求。大多数基于Windows的应用程序都支持DDE。

来看下MSDN官方的介绍：

Dynamic Data Exchange (DDE) is a form of interprocess communication that uses shared memory to exchange data between applications. Applications can use DDE for one-time data transfers and for ongoing exchanges and updating of data.

Dynamic Data Exchange (DDE) differs from the clipboard data-transfer mechanism. One difference is that the clipboard is almost always used as a one-time response to a specific action by the user — such as clicking Paste from a menu. Although DDE can also be initiated by a user, it typically continues without the user‘s further involvement.

The Dynamic Data Exchange Management Library (DDEML) provides an interface that simplifies the task of adding DDE capability to an application. Instead of sending, posting, and processing DDE messages directly, an application uses the functions provided by the DDEML to manage DDE conversations. A DDE conversation is the interaction between client and server applications. The DDEML also provides a means for managing the strings and data shared among DDE applications. Instead of using atoms and pointers to shared memory objects, DDE applications create and exchange string handles, which identify strings, and data handles, which identify DDE objects. The DDEML provides a function (DdeNameService) that enables a server application to register the service names it supports. The service names are then broadcast to other applications in the system, which use the names to connect to the server. The DDEML also ensures compatibility among DDE applications by requiring them to implement the DDE protocol in a consistent manner.

Existing applications using the message-based DDE protocol are fully compatible with those that use the DDEML; that is, an application using message-based DDE can establish conversations and perform transactions with applications using the DDEML. Instead of using DDE messages in your new application, take advantage of the DDEML and the many improvements it offers.

To use the DDEML, you must include the DDEML.H header file in your source files, link with the USER32.LIB file, and ensure that the DDEML.DLL file resides in the system‘s path.

Whenever a DDEML function fails, an application can call the DdeGetLastError function to determine the cause of the failure. DdeGetLastError returns an error value that specifies the cause of the most recent error.

 这一节以后再详细讨论。

参考：https://msdn.microsoft.com/en-us/library/windows/desktop/ms648711%28v=vs.85%29.aspx

https://msdn.microsoft.com/en-us/library/windows/desktop/ms648712%28v=vs.85%29.aspx

 七、对象链接与嵌入OLE

应用程序利用对象连接与嵌入(OLE)技术管理复合文档(由多种数据格式组成的文档)，OLE提供使某应用程序更容易调用其它应用程序进行数据编辑的 服务。例如，OLE支持的字处理器可以嵌套电子表格，当用户要编辑电子表格时OLE库可自动启动电子表格编辑器。当用户退出电子表格编辑器时，该表格已在 原始字处理器文档中得到更新。在这里电子表格编辑器变成了字处理器的扩展，而如果使用DDE，用户要显式地启动电子表格编辑器。
同DDE技术相同，大多数基于Windows的应用程序都支持OLE技术。

Applications that use OLE manage compound documents—that is, documents made up of data from a variety of different applications. OLE provides services that make it easy for applications to call on other applications for data editing. For example, a word processor that uses OLE could embed a graph from a spreadsheet. The user could start the spreadsheet automatically from within the word processor by choosing the embedded chart for editing. OLE takes care of starting the spreadsheet and presenting the graph for editing. When the user quit the spreadsheet, the graph would be updated in the original word processor document. The spreadsheet appears to be an extension of the word processor.

The foundation of OLE is the Component Object Model (COM). A software component that uses COM can communicate with a wide variety of other components, even those that have not yet been written. The components interact as objects and clients. Distributed COM extends the COM programming model so that it works across a network.

Key Point:  OLE supports compound documents and enables an application to include embedded or linked data that, when chosen, automatically starts another application for data editing. This enables the application to be extended by any other application that uses OLE. COM objects provide access to an object‘s data through one or more sets of related functions, known as interfaces. For more information, see COM and ActiveX Object Services.

八、DLL

Win32动态连接库(DLL)中的全局数据可以被调用DLL的所有进程共享，这就又给进程间通信开辟了一条新的途径，当然访问时要注意同步问题。虽然可以通过DLL进行进程间数据共享，但从数据安全的角度考虑，我们并不提倡这种方法，使用带有访问权限控制的共享内存的方法更好一些。

九、远程过程调用

Win32 API提供的远程过程调用(RPC)使应用程序可以使用远程调用函数，这使在网络上用RPC进行进程通信就像函数调用那样简单。RPC既可以在单机不同进程间使用也可以在网络中使用。
由于Win32 API提供的RPC服从OSF-DCE (Open Software Foundation Distributed Computing Environment)标准。所以通过 Win32 API编写的RPC应用程序能与其它操作系统上支持DEC的RPC应用程序通信。使用RPC开发者可以建立高性能、紧密耦合的分布式应用程 序。

RPC enables applications to call functions remotely. Therefore, RPC makes IPC as easy as calling a function. RPC operates between processes on a single computer or on different computers on a network.

The RPC provided by Windows is compliant with the Open Software Foundation (OSF) Distributed Computing Environment (DCE). This means that applications that use RPC are able to communicate with applications running with other operating systems that support DCE. RPC automatically supports data conversion to account for different hardware architectures and for byte-ordering between dissimilar environments.

RPC clients and servers are tightly coupled but still maintain high performance. The system makes extensive use of RPC to facilitate a client/server relationship between different parts of the operating system.

Key Point:  RPC is a function-level interface, with support for automatic data conversion and for communications with other operating systems. Using RPC, you can create high-performance, tightly coupled distributed applications. For more information, see Microsoft RPC Components.

十、NetBios

Win32 API提供NetBios函数用于处理低级网络控制，这主要是为IBM NetBios系统编写与Windows的接口。除非那些有特殊低级网络功能要求的应用程序，其它应用程序最好不要使用NetBios函数来进行进程间通信。

十一、Sockets

Windows Sockets规范是以U.C.Berkeley大学BSD UNIX中流行的Socket接口为范例定义的一套Windows下的 网络编程接口。除了Berkeley Socket原有的库函数以外，还扩展了一组针对Windows的函数，使程序员可以充分利用Windows的消息 机制进行编程。
现在通过Sockets实现进程通信的网络应用越来越多，这主要的原因是Sockets的跨平台性要比其它IPC机制好得多，另 外 WinSock 2.0不仅支持TCP/IP协议，而且还支持其它协议(如IPX)。Sockets的唯一缺点是它支持的是底层通信操作，这使得在单机的 进程间进行简单数据传递不太方便，这时使用下面将介绍的WM_COPYDATA消息将更合适些。

Windows Sockets is a protocol-independent interface. It takes advantage of the communication capabilities of the underlying protocols. In Windows Sockets 2, a socket handle can optionally be used as a file handle with the standard file I/O functions.

Windows Sockets are based on the sockets first popularized by Berkeley Software Distribution (BSD). An application that uses Windows Sockets can communicate with other socket implementation on other types of systems. However, not all transport service providers support all available options.

Key Point:  Windows Sockets is a protocol-independent interface capable of supporting current and emerging networking capabilities. For more information, see Windows Sockets 2.

十二、WM_COPYDATA消息

WM_COPYDATA是一种非常强大却鲜为人知的消息。当一个应用向另一个应用传送数据时，发送方只需使用调用SendMessage函数，参数是 目的窗口的句柄、传递数据的起始地址、WM_COPYDATA消息。接收方只需像处理其它消息那样处理WM_COPY DATA消息，这样收发双方就实现 了数据共享。WM_COPYDATA是一种非常简单的方法，它在底层实际上是通过文件映射来实现的。它的缺点是灵活性不高，并且它只能用于Windows平台的单机环境下。

Data copy enables an application to send information to another application using the WM_COPYDATA message. This method requires cooperation between the sending application and the receiving application. The receiving application must know the format of the information and be able to identify the sender. The sending application cannot modify the memory referenced by any pointers.

Key Point:  Data copy can be used to quickly send information to another application using Windows messaging. For more information, see Data Copy.

 参考：http://www.codeproject.com/Articles/115/Inter-Process-Communication-using-WM-COPYDATA

总结：Interprocess communication

参考：https://msdn.microsoft.com/en-us/library/windows/desktop/aa365574%28v=vs.85%29.aspx

http://blog.csdn.net/tujiaw/article/details/6588291