C++与Python之间的通信(IPC)

5
我有一个应用服务器(server.py),和一个 C++ 客户端(client.exe)。客户端通过“命名管道”将变量发送到 server.py。
问题是,当我从 client.exe 发送例如“来自客户端的默认消息”时,在 server.py 中只会产生“D”(仅发送第一个字符)。
有人能帮我吗?
C++

server.py

from ctypes import *

PIPE_ACCESS_DUPLEX = 0x3
PIPE_TYPE_MESSAGE = 0x4
PIPE_READMODE_MESSAGE = 0x2
PIPE_WAIT = 0
PIPE_UNLIMITED_INSTANCES = 255
BUFSIZE = 4096
NMPWAIT_USE_DEFAULT_WAIT = 0
INVALID_HANDLE_VALUE = -1
ERROR_PIPE_CONNECTED = 535

MESSAGE = "Default answer from server\0"
szPipename = "\\\\.\\pipe\\mynamedpipe"


def ReadWrite_ClientPipe_Thread(hPipe):
    chBuf = create_string_buffer(BUFSIZE)
    cbRead = c_ulong(0)
    while 1:
        fSuccess = windll.kernel32.ReadFile(hPipe, chBuf, BUFSIZE,
byref(cbRead), None)
        if ((fSuccess ==1) or (cbRead.value != 0)):
            print chBuf.value
            cbWritten = c_ulong(0)
            fSuccess = windll.kernel32.WriteFile(hPipe,c_char_pc_char_p(MESSAGE),len(MESSAGE),byref(cbWritten),None)
        else:
            break
        if ( (not fSuccess) or (len(MESSAGE) != cbWritten.value)):
            print "Could not reply to the client's request from the pipe"
            break
        else:
            print "Number of bytes written:", cbWritten.value

    windll.kernel32.FlushFileBuffers(hPipe)
    windll.kernel32.DisconnectNamedPipe(hPipe)
    windll.kernel32.CloseHandle(hPipe)
    return 0

def main():
    THREADFUNC = CFUNCTYPE(c_int, c_int)
    thread_func = THREADFUNC(ReadWrite_ClientPipe_Thread)
    while 1:
        hPipe = windll.kernel32.CreateNamedPipeA(szPipename,PIPE_ACCESS_DUPLEX,PIPE_TYPE_MESSAGE | PIPE_READMODE_MESSAGE | PIPE_WAIT, PIPE_UNLIMITED_INSTANCES, BUFSIZE, BUFSIZE, NMPWAIT_USE_DEFAULT_WAIT,None)
        if (hPipe == INVALID_HANDLE_VALUE):
            print "Error in creating Named Pipe"
            return 0

        fConnected = windll.kernel32.ConnectNamedPipe(hPipe, None)
        if ((fConnected == 0) and (windll.kernel32.GetLastError() == ERROR_PIPE_CONNECTED)):
            fConnected = 1
        if (fConnected == 1):
            dwThreadId = c_ulong(0)
            hThread = windll.kernel32.CreateThread(None, 0, thread_func, hPipe, 0, byref(dwThreadId))
            if (hThread == -1):
                print "Create Thread failed"
                return 0
            else:
                windll.kernel32.CloseHandle(hThread)
        else:
            print "Could not connect to the Named Pipe"
            windll.kernel32.CloseHandle(hPipe)
    return 0


if __name__ == "__main__":
    main()

Client.cpp

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

#define BUFSIZE 512

int _tmain(int argc, TCHAR *argv[]) 
{ 
   HANDLE hPipe; 
   LPTSTR lpvMessage=TEXT("Default message from client."); 
   TCHAR  chBuf[BUFSIZE]; 
   BOOL   fSuccess = FALSE; 
   DWORD  cbRead, cbToWrite, 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) 
      {
         _tprintf( TEXT("Could not open pipe. GLE=%d\n"), GetLastError() ); 
         return -1;
      }

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

      if ( ! WaitNamedPipe(lpszPipename, 20000)) 
      { 
         printf("Could not open pipe: 20 second wait timed out."); 
         return -1;
      } 
   } 

// 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) 
   {
      _tprintf( TEXT("SetNamedPipeHandleState failed. GLE=%d\n"), GetLastError() ); 
      return -1;
   }

// Send a message to the pipe server. 

   cbToWrite = (lstrlen(lpvMessage)+1)*sizeof(TCHAR);
   _tprintf( TEXT("Sending %d byte message: \"%s\"\n"), cbToWrite, lpvMessage); 

   fSuccess = WriteFile( 
      hPipe,                  // pipe handle 
      lpvMessage,             // message 
      cbToWrite,              // message length 
      &cbWritten,             // bytes written 
      NULL);                  // not overlapped 

   if ( ! fSuccess) 
   {
      _tprintf( TEXT("WriteFile to pipe failed. GLE=%d\n"), GetLastError() ); 
      return -1;
   }

   printf("\nMessage sent to server, receiving reply as follows:\n");

   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 

   if ( ! fSuccess)
   {
      _tprintf( TEXT("ReadFile from pipe failed. GLE=%d\n"), GetLastError() );
      return -1;
   }



   CloseHandle(hPipe); 

   return 0; 
}
2个回答

4

如果你打印出服务器接收到的缓冲区的 .raw 格式,你会发现它实际上收到了整个信息:

> print repr(chBuf.raw)

'D\x00e\x00f\x00a\x00u\x00l\x00t\x00 \x00m\x00e\x00s\x00s\x00a\x00g\x00e\x00 \x00f\x00r\x00o\x00m\x00\x00c\x00l\x00i\x00e\x00n\x00t\x00.\x00\x00\x00\x00\x00 ... \x00\x00'

问题在于合法字符之间存在空值(\x00),当您尝试打印chBuf.value时,这些空值看起来像是空终止符。那么为什么会有这么多空值呢?原因是您的C ++客户端正在发送wchar_t *消息(使用LPTSTR),但Python服务器正在期望char *字符串。

更改此行:

chBuf = create_string_buffer(BUFSIZE)

转换为:

chBuf = create_unicode_buffer(BUFSIZE)

这应该可以解决问题。

哦,另外,看起来你在这里复制粘贴出现了错误:

fSuccess = windll.kernel32.WriteFile(hPipe,c_char_pc_char_p(MESSAGE),len(MESSAGE),byref(cbWritten),None)

应该是:

fSuccess = windll.kernel32.WriteFile(hPipe, c_char_p(MESSAGE),len(MESSAGE),byref(cbWritten),None)

在 Python 代码中,我遇到了一个名称错误,直到我进行了更改才解决了这个问题。


1
更具体地说,Windows的TEXT()宏将根据UNICODE是否被#define定义来生成ANSI或UTF-16字符串。请参阅http://msdn.microsoft.com/en-us/library/windows/desktop/dd374074(v=vs.85).aspx。 - Clayton Hughes
不错!所以有一种方法可以在C++端或Python端修复代码 :) - NattyBumppo

-1
也许服务器应该尝试在循环中从管道中读取数据,直到达到您与客户端协议规定的所有预期数据(例如,直到读取到空终止符号)。

只有在我使用两种不同的语言运行时才会出现这种情况。但是如果在Python和C++中使用相同的语言,则两者都可以正常运行。 - Varanka
@Varanka 或许读取缓冲区不同。我认为最好的方法仍然是读取所有预期数据(或到达EOF-管道已关闭)。 - selalerer

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