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; }
