multithreading - Concurrent read/write of named pipe in Java (on windows)

Question

I'm trying to provide communication between a C# app and a Java app on windows using named pipes with the method described by v01ver in this question: How to open a Windows named pipe from Java?

I'm running into a problem on the Java side because I have a reader thread constantly waiting for input on the pipe and when I try to write to the pipe from my main thread it gets stuck forever.

final RandomAccessFile pipe;
try {
   pipe = new RandomAccessFile("\\.\pipe\mypipe", "rw");
}
catch (FileNotFoundException ex) {
   ex.printStackTrace();
   return;
}

Thread readerThread = new Thread(new Runnable() {
   @Override
   public void run() {
      String line = null;
      try {
         while (null != (line = pipe.readLine())) {
            System.out.println(line);
         }
      }
      catch (IOException ex) {
         ex.printStackTrace();
      }
   }
});
readerThread.start();

try { Thread.sleep(500); } catch (InterruptedException e) {}

try {
   System.out.println("Writing a message...");
   pipe.write("Hello there.
".getBytes());
   System.out.println("Finished.");
}
catch (IOException ex) {
   ex.printStackTrace();
}

The output is:

Writing a message...

and then it waits forever.

How can I write to a named pipe while waiting for input in another thread?

Answer 1

This is expected behaviour of pipes. It is supposed to hang untill other process connects to the pipe and reads it.