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[英]Interprocess Communication between C++ app and Java App in Windows OS environment
[英]NamedPipe interprocess between c++ and Java application
我需要从c ++端启动一个命名管道服务器,并获取一个Java应用程序以从管道读取数据。
对于创建管道的C ++端,我遵循了MSDN上的示例: https : //msdn.microsoft.com/zh-cn/library/windows/desktop/aa365603(v= vs.85) .aspx
从Java端开始,我做了一段hacky代码来测试:
Thread readerThread = new Thread( new Runnable()
{
@Override
public void run()
{
String line = null;
while( true )
{
try
{
final RandomAccessFile pipe =
new RandomAccessFile( "\\\\\\\\.\\\\pipe\\\\smarts_interprocess", "r" );
while( null != ( line = pipe.readLine() ) )
{
s_logger.warning( line );
}
}
catch( IOException ex )
{
s_logger.severe( ex.getMessage() );
try
{
Thread.sleep( 1000 );
}
catch( InterruptedException e )
{
s_logger.info( "nothing available, I will sleep for a second" );
}
}
}
}
} );
readerThread.start();
C ++附加代码:
void Pipe::startMessageLoop()
{
DWORD dwWait{};
BOOL fSuccess;
fPendingIO = ConnectToNewClient(m_inputHandle, &oOverlap_);
while (true)
{
dwWait = ::WaitForSingleObject(oOverlap_.hEvent, INFINITE);
if (dwWait == WAIT_FAILED)
{
::CloseHandle(oOverlap_.hEvent);
std::cout << "failed to WaitForSingleObject.." << std::endl;
}
if (fPendingIO)
{
DWORD cbRet;
fSuccess = GetOverlappedResult(
m_inputHandle, // handle to pipe
&oOverlap_, // OVERLAPPED structure
&cbRet, // bytes transferred
FALSE); // do not wait
switch (dwState)
{
// Pending connect operation
case CONNECTING_STATE:
if (!fSuccess)
{
printf("Error %d.\n", GetLastError());
return;
}
dwState = WRITING_STATE;
break;
// Pending write operation
case WRITING_STATE:
if (!fSuccess)
{
DisconnectAndReconnect();
continue;
}
break;
default:
{
printf("Invalid pipe state.\n");
return;
}
}
}
std::string message = "naive message from server";
std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> converter;
std::wstring data = converter.from_bytes(message.c_str());
DWORD numBytesWritten = 0;
switch (dwState)
{
case WRITING_STATE:
fSuccess = WriteFile(
m_inputHandle, // handle to our outbound pipe
data.c_str(), // data to send
wcslen(data.c_str()) * sizeof(wchar_t), // length of data to send (bytes)
&numBytesWritten, // will store actual amount of data sent
NULL // not using overlapped IO
);
// FlushFileBuffers(m_inputHandle);
// The write operation completed successfully.
if (fSuccess)
{
fPendingIO = FALSE;
std::this_thread::sleep_for(std::chrono::milliseconds(5000));
dwState = WRITING_STATE;
continue;
}
// The write operation is still pending.
if (!fSuccess && (GetLastError() == ERROR_IO_PENDING))
{
fPendingIO = TRUE;
continue;
}
// An error occurred; disconnect from the client.
DisconnectAndReconnect();
break;
default:
{
printf("Invalid pipe state.\n");
return;
}
}
}
}
它可以连接到管道,没有任何问题,但是唯一的问题是,在C ++进程完成之前,Java端无法获取在c ++端上编写的数据(终止VS的调试程序是我的意思)。
只要我的C ++进程仍在运行,它就会挂在readLine的位置:line = pipe.readLine()
有人对此有任何想法吗?
据我所知-如果您在服务器端使用了完全相同的MSDN代码-服务器在将任何内容写入管道之前都在等待输入。 如果您的客户端从不发送任何内容,则pipe.readLine
将阻塞,直到断开连接为止。
Java不是我的事,但我猜测服务器的响应还必须包含换行符,以便readLine
返回。
如果您在readLine()
被阻止,则对等方不会发送行。 当对等方退出时,其解除阻塞的原因是读取器遇到流的末尾,并返回到目前为止接收到的数据。
您需要找出对等方正在发送的内容,并使用适当的读取方法。 显然,这不是行,因此readLine()
是完成此工作的错误工具。
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