在C ++和Python之间进行通信（IPC）

Question

我有应用程序服务器（server.py）和C + +作为客户端（client.exe）。 Client.exe通过“命名管道”将变量发送到server.py。

问题是当我从server.py中的client.exe发送例如“来自客户端的默认消息”时，只生成“D”（仅第一个字符发送）。

谁能帮我？？

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; 
}

Answer 1

如果您打印出服务器收到的缓冲区的.raw，您可以看到它实际上收到了整条消息：

> 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'

问题是在合法字符之间存在空值（\\ x00），当您尝试打印chBuf.value时，这些值看起来像空终止符。 那么为什么所有的零呢？ 这是因为您的C ++客户端正在发送wchar_t *消息（使用LPTSTR），但Python服务器需要char *字符串。

改变这一行：

chBuf = create_string_buffer(BUFSIZE)

对此：

chBuf = create_unicode_buffer(BUFSIZE)

这应该可以解决问题。

哦，看起来你在这里有一个复制粘贴错误：

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

它应该是：

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

在我更改之前，我在Python代码中出现了名称错误。

Answer 2

也许服务器应该尝试从循环中读取管道，直到达到预期到达的所有数据（根据您与客户端的协议，例如，直到读取空终止符）。