Windows进程间通信—命名管道

命名管道是通过网络来完成进程间的通信，它屏蔽了底层的网络协议细节。我们在不了解网络协议的情况下，也可以利用命名管道来实现进程间的通信。与Socket网络通信相比，命名管道不再需要编写身份验证的代码。将命名管道作为一种网络编程方案时，它实际上建立了一个C/S通信体系，并在其中可靠的传输数据。命名管道服务器和客户机的区别在于：服务器是唯一一个有权创建命名管道的进程，也只有它能接受管道客户机的连接请求。而客户机只能同一个现成的命名管道服务器建立连接。命名管道服务器只能在WindowsNT或Windows2000上创建，不过可以是客户机。命名管道提供了两种基本通信模式，字节模式和消息模式。在字节模式中，数据以一个连续的字节流的形式在客户机和服务器之间流动。而在消息模式中，客户机和服务器则通过一系列不连续的数据单位进行数据的收发，每次在管道上发出一条消息后，它必须作为一条完整的消息读入。

服务端代码流程：

1、创建命名管道：CreateNamedPipe

2、等待客户端连接：ConnectNamedPipe

3、读取客户端请求数据：ReadFile

4、向客户端回复数据：WriteFile

5、关闭连接：DisconnectNamedPipe

6、关闭管道：CloseHandle

#include "stdafx.h"
#include <windows.h>
#include <strsafe.h>

#define BUFSIZE 4096

DWORD WINAPI InstanceThread(LPVOID);
VOID GetAnswerToRequest(LPTSTR, LPTSTR, LPDWORD);

int _tmain(VOID)
{
BOOL fConnected;
DWORD dwThreadId;
HANDLE hPipe, hThread;
LPTSTR lpszPipename = TEXT("\\\\.\\pipe\\mynamedpipe");

// The main loop creates an instance of the named pipe and
// then waits for a client to connect to it. When the client
// connects, a thread is created to handle communications
// with that client, and the loop is repeated.

for (;;)
{
hPipe = CreateNamedPipe(
lpszPipename,             // pipe name
PIPE_ACCESS_DUPLEX,       // read/write access
PIPE_TYPE_MESSAGE |       // message type pipe
PIPE_READMODE_MESSAGE |   // message-read mode
PIPE_WAIT,                // blocking mode
PIPE_UNLIMITED_INSTANCES, // max. instances
BUFSIZE,                  // output buffer size
BUFSIZE,                  // input buffer size
0,                        // client time-out
NULL);                    // default security attribute

if (hPipe == INVALID_HANDLE_VALUE)
{
printf("CreatePipe failed");
return 0;
}

// Wait for the client to connect; if it succeeds,
// the function returns a nonzero value. If the function
// returns zero, GetLastError returns ERROR_PIPE_CONNECTED.

fConnected = ConnectNamedPipe(hPipe, NULL) ? TRUE : (GetLastError() == ERROR_PIPE_CONNECTED);

if (fConnected)
{
// Create a thread for this client.
hThread = CreateThread(
NULL,              // no security attribute
0,                 // default stack size
InstanceThread,    // thread proc
(LPVOID) hPipe,    // thread parameter
0,                 // not suspended
&dwThreadId);      // returns thread ID

if (hThread == NULL)
{
printf("CreateThread failed");
return 0;
}
else CloseHandle(hThread);
}
else
{
// The client could not connect, so close the pipe.
CloseHandle(hPipe);
}
}
return 1;
}

DWORD WINAPI InstanceThread(LPVOID lpvParam)
{
TCHAR chRequest[BUFSIZE];
TCHAR chReply[BUFSIZE];
DWORD cbBytesRead, cbReplyBytes, cbWritten;
BOOL fSuccess;
HANDLE hPipe;

// The thread's parameter is a handle to a pipe instance.

hPipe = (HANDLE) lpvParam;

while (1)
{
// Read client requests from the pipe.
fSuccess = ReadFile(
hPipe,        // handle to pipe
chRequest,    // buffer to receive data
BUFSIZE*sizeof(TCHAR), // size of buffer
&cbBytesRead, // number of bytes read
NULL);        // not overlapped I/O

if (! fSuccess || cbBytesRead == 0)
break;
printf((const char*)chRequest);

GetAnswerToRequest(chRequest, chReply, &cbReplyBytes);

// Write the reply to the pipe.
fSuccess = WriteFile(
hPipe,        // handle to pipe
chReply,      // buffer to write from
cbReplyBytes, // number of bytes to write
&cbWritten,   // number of bytes written
NULL);        // not overlapped I/O

if (! fSuccess || cbReplyBytes != cbWritten) break;
}

// Flush the pipe to allow the client to read the pipe's contents
// before disconnecting. Then disconnect the pipe, and close the
// handle to this pipe instance.

FlushFileBuffers(hPipe);
DisconnectNamedPipe(hPipe);
CloseHandle(hPipe);

return 1;
}

VOID GetAnswerToRequest(LPTSTR chRequest,
LPTSTR chReply, LPDWORD pchBytes)
{
_tprintf( TEXT("%s\n"), chRequest );
StringCchCopy( chReply, BUFSIZE, TEXT("Default answer from server") );
*pchBytes = (lstrlen(chReply)+1)*sizeof(TCHAR);
}
/* 何问起 hovertree.com */

客户端代码流程：

1、打开命名管道：CreateFile

2、等待服务端响应：WaitNamedPipe

3、切换管道为读模式：SetNamedPipeHandleState

4、向服务端发数据：WriteFile

5、读服务端返回的数据：ReadFile

6、关闭管道：CloseHandle

#include "stdafx.h"
#include <windows.h>
#include <conio.h>

#define BUFSIZE 512

int _tmain(int argc, TCHAR *argv[])
{
HANDLE hPipe;
LPTSTR lpvMessage=TEXT("Default message from client");
TCHAR chBuf[BUFSIZE];
BOOL fSuccess;
DWORD cbRead, cbWritten, dwMode;
LPTSTR lpszPipename = TEXT("\\\\.\\pipe\\mynamedpipe");

if( argc > 1 )
lpvMessage = argv[1];

// Try to open a named pipe; wait for it, if necessary.

while (1)
{
hPipe = CreateFile(
lpszPipename,   // pipe name
GENERIC_READ |  // read and write access
GENERIC_WRITE,
0,              // no sharing
NULL,           // default security attributes
OPEN_EXISTING,  // opens existing pipe
0,              // default attributes
NULL);          // no template file

// Break if the pipe handle is valid.

if (hPipe != INVALID_HANDLE_VALUE)
break;

// Exit if an error other than ERROR_PIPE_BUSY occurs.

if (GetLastError() != ERROR_PIPE_BUSY)
{
printf("Could not open pipe");
return 0;
}

// All pipe instances are busy, so wait for 20 seconds.

if (!WaitNamedPipe(lpszPipename, 20000))
{
printf("Could not open pipe");
return 0;
}
}

// The pipe connected; change to message-read mode.

dwMode = PIPE_READMODE_MESSAGE;
fSuccess = SetNamedPipeHandleState(
hPipe,    // pipe handle
&dwMode,  // new pipe mode
NULL,     // don't set maximum bytes
NULL);    // don't set maximum time
if (!fSuccess)
{
printf("SetNamedPipeHandleState failed");
return 0;
}  // 何问起 hovertree.com

// Send a message to the pipe server.

fSuccess = WriteFile(
hPipe,                  // pipe handle
lpvMessage,             // message
(lstrlen(lpvMessage)+1)*sizeof(TCHAR), // message length
&cbWritten,             // bytes written
NULL);                  // not overlapped
if (!fSuccess)
{
printf("WriteFile failed");
return 0;
}

do
{
// Read from the pipe.

fSuccess = ReadFile(
hPipe,    // pipe handle
chBuf,    // buffer to receive reply
BUFSIZE*sizeof(TCHAR),  // size of buffer
&cbRead,  // number of bytes read
NULL);    // not overlapped

if (! fSuccess && GetLastError() != ERROR_MORE_DATA)
break;

_tprintf( TEXT("%s\n"), chBuf );
} while (!fSuccess);  // repeat loop if ERROR_MORE_DATA

getch();

CloseHandle(hPipe);

return 0;
}

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