Named pipe is connected while checking if it exists from Java - eclipse

Question

I am using Lukas Thomsen's named pipe example to create a pipe server in C++ and a reader in Java.
On the Java side I want to wait until the Named Pipe is created by C++ server.
File file = new File("\\\\.\\pipe\\Pipe");
while(!file.exists());
InputStream input = new FileInputStream(file);
However, the file.exists() somehow connects the named pipe and instantiating FileInputStream throws following exception:
java.io.FileNotFoundException: \\.\pipe\Pipe (All pipe instances are busy)
at java.io.FileInputStream.open0(Native Method)
at java.io.FileInputStream.open(Unknown Source)
at java.io.FileInputStream.<init>(Unknown Source)
Here is the snippet of c++ server:
int main(void)
{
HANDLE hPipe;
char buffer[1024];
DWORD dwRead;
hPipe = CreateNamedPipe(TEXT("\\\\.\\pipe\\Pipe"),
PIPE_ACCESS_DUPLEX | PIPE_TYPE_BYTE | PIPE_READMODE_BYTE, // FILE_FLAG_FIRST_PIPE_INSTANCE is not needed but forces CreateNamedPipe(..) to fail if the pipe already exists...
PIPE_WAIT,
1,
1024 * 16,
1024 * 16,
NMPWAIT_USE_DEFAULT_WAIT,
NULL);
while (hPipe != INVALID_HANDLE_VALUE)
{
if (ConnectNamedPipe(hPipe, NULL) != FALSE) // wait for someone to connect to the pipe
{
cout<<"connected";
//do amazing stuff after being connected.
}
DisconnectNamedPipe(hPipe);
}
return 0;
}
So what it the proper way to wait for named pipe in Java without throwing this error?

Answer 1

The reason this problem occurs is that File.exists() on Windows is implemented using a sequence of native function calls to CreateFile, GetFileInformationByHandle and CloseHandle. See the getFileInformation function in the Java source code. From a named pipe perspective this is bad because on Windows named pipes have to be reset between uses and the CreateFile call in that native function counts as a use.
The solution is to ask forgiveness rather than permission when opening the named pipe on the Java side. Something along the lines of:
File file = new File("\\\\.\\pipe\\Pipe");
while (true) {
try {
return new FileInputStream(file);
} catch (IOException e) {
Thread.sleep(20);
}
}
(Obviously you might not want to loop forever in practice, but the code in the question did.)