Deadlock... i think

java-programmer, Deadlock... i think I apologize in advance for the length of the note, and the source code
included.

I posted earlier under the title "Double streams", where i wanted to
use an RMI object as a sort of proxy for two clients to exchange data
via streams. I kinda failed, but now i'm trying something new. This
doesn't work either, but this time i think someone might be able to
solve it, since i'm not adept at using threads and i think that's
where the problem is. :)

The source for ByteHolder and RemoteByteHolder is included below. A
server is run, making a ByteHolder, BH, available via RMI.

Client A obtains the reference to BH, and passes this on to its
FooOutputStream, which extends OutputStream and implements the
write(int b) method by calling putByte(b) on BH.

Client B also gets BH, passes this to FooInputStream, which extends
InputStream and implements read() by calling getByte() on BH.

What i did to test was:
- run the server
- client A wraps the FooOutputStream in a PrintWriter, and
println("foo") is called on it
- client B wraps FooInputStream in a InputStreamReader, which is
then wrapped in a BufferedReader, and readLine() is called on that

The data then goes, one byte at the time, from client A to client B.
Client A stops running, but Client B just sorta hangs around... in a
deadlock i presume. I can make it return and print out the read line
by doing one of two things:
- kill the server
- manually send a -1 to client B

When i've used streams before, i didn't have to send a -1 in order to
get the reading side to get on with it - it just happened magically. I
also don't understand why killing the server make things better...

Can anyone explain this or, as an alternative, suggest a better way to
exchange bytes via RMI. I just really wanted to make streams work. :)

Oh, another thing. To make the server available, i've made it Runnable
and in the run i have a while(true) loop, that makes the thread sleep
for a chunk of time. Maybe that is a problem, too?

Regards,
Carsten H. Pedersen

----------- SOURCE BELOW -------------

package streams.holder;

import java.rmi.Remote;
import java.rmi.RemoteException;

public interface RemoteByteHolder extends Remote {
int getByte() throws RemoteException;
void putByte(int b) throws RemoteException;
}

...

package streams.holder;
import java.rmi.RemoteException;

public class ByteHolder implements RemoteByteHolder {

private int theByte;
private boolean stored = false;

public synchronized int getByte() throws RemoteException {
while(!stored) {
try {
wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

System.out.println("hb: get: "+theByte);
int i = theByte;
stored = false;
notifyAll();
return i;
}

public synchronized void putByte(int b) throws RemoteException {
while(stored) {
try {
wait();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

System.out.println("bh: put: "+b);
stored = true;
theByte = b;
notifyAll();
}

}

java-programmer >> Deadlock... i think
"Carsten H. Pedersen" <email***@***.com> wrote in message
news:43f6fa27$0$67264$email***@***.com...
>
> I posted earlier under the title "Double streams", where i wanted to use
> an RMI object as a sort of proxy for two clients to exchange data via
> streams. I kinda failed, but now i'm trying something new. This doesn't
> work either, but this time i think someone might be able to solve it,
> since i'm not adept at using threads and i think that's where the problem
> is. :)

If you don't get any answers for 1 or 2 days, try posting this to
comp.lang.java.programmer. There's a lot of people there who are familiar
with threading who don't read this newsgroup.

If you post there too early though, you get accused of multiposting.

- Oliver

java-programmer >> Deadlock... i think Hi Carsten,

What does your readLine code look like?

Are you doing something like:

while ((line = readLine())!=null) ...

"Carsten H. Pedersen" <email***@***.com> wrote in message
news:43f6fa27$0$67264$email***@***.com...
>I apologize in advance for the length of the note, and the source code
>included.
>
> I posted earlier under the title "Double streams", where i wanted to use
> an RMI object as a sort of proxy for two clients to exchange data via
> streams. I kinda failed, but now i'm trying something new. This doesn't
> work either, but this time i think someone might be able to solve it,
> since i'm not adept at using threads and i think that's where the problem
> is. :)
>
> The source for ByteHolder and RemoteByteHolder is included below. A server
> is run, making a ByteHolder, BH, available via RMI.
>
> Client A obtains the reference to BH, and passes this on to its
> FooOutputStream, which extends OutputStream and implements the write(int
> b) method by calling putByte(b) on BH.
>
> Client B also gets BH, passes this to FooInputStream, which extends
> InputStream and implements read() by calling getByte() on BH.
>
> What i did to test was:
> - run the server
> - client A wraps the FooOutputStream in a PrintWriter, and println("foo")
> is called on it
> - client B wraps FooInputStream in a InputStreamReader, which is then
> wrapped in a BufferedReader, and readLine() is called on that
>
> The data then goes, one byte at the time, from client A to client B.
> Client A stops running, but Client B just sorta hangs around... in a
> deadlock i presume. I can make it return and print out the read line by
> doing one of two things:
> - kill the server
> - manually send a -1 to client B
>
> When i've used streams before, i didn't have to send a -1 in order to get
> the reading side to get on with it - it just happened magically. I also
> don't understand why killing the server make things better...
>
> Can anyone explain this or, as an alternative, suggest a better way to
> exchange bytes via RMI. I just really wanted to make streams work. :)
>
> Oh, another thing. To make the server available, i've made it Runnable and
> in the run i have a while(true) loop, that makes the thread sleep for a
> chunk of time. Maybe that is a problem, too?
>
> Regards,
> Carsten H. Pedersen
>
>
> ----------- SOURCE BELOW -------------
>
>
> package streams.holder;
>
> import java.rmi.Remote;
> import java.rmi.RemoteException;
>
> public interface RemoteByteHolder extends Remote {
> int getByte() throws RemoteException;
> void putByte(int b) throws RemoteException;
> }
>
> ...
>
> package streams.holder;
> import java.rmi.RemoteException;
>
> public class ByteHolder implements RemoteByteHolder {
>
> private int theByte;
> private boolean stored = false;
>
> public synchronized int getByte() throws RemoteException {
> while(!stored) {
> try {
> wait();
> } catch (InterruptedException e) {
> // TODO Auto-generated catch block
> e.printStackTrace();
> }
> }
>
> System.out.println("hb: get: "+theByte);
> int i = theByte;
> stored = false;
> notifyAll();
> return i;
> }
>
> public synchronized void putByte(int b) throws RemoteException {
> while(stored) {
> try {
> wait();
> } catch (InterruptedException e) {
> // TODO Auto-generated catch block
> e.printStackTrace();
> }
> }
>
> System.out.println("bh: put: "+b);
> stored = true;
> theByte = b;
> notifyAll();
> }
>
> }