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;
TCHAR chReply;
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;
BOOL fSuccess;
DWORD cbRead, cbWritten, dwMode;
LPTSTR lpszPipename = TEXT("\\\\.\\pipe\\mynamedpipe");
if( argc > 1 )
lpvMessage = argv;
// 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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