Re: Interplatform (interprocess, interlanguage) communication

From:

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>

Newsgroups:

comp.lang.java.programmer

Date:

Sat, 04 Feb 2012 18:35:27 -0500

Message-ID:

<4f2dc0c0$0$294$14726298@news.sunsite.dk>

On 2/4/2012 7:59 AM, Robert Klemme wrote:

On 03.02.2012 23:56, Arne Vajh?j wrote:

On 2/3/2012 4:44 PM, Robert Klemme wrote:

On 02/03/2012 08:52 PM, Stefan Ram wrote:

?X? below is another language than Java, for example,
VBA, C#, or C.

When an X process and a Java process have to exchange
information on the same computer, what possibilites are
there? The Java process should act as a client, sending
commands to the X process and also wants to read answers
from the X process. So, the X process is a kind of server.

My criteria are: reliability and it should not be extremely
slow (say exchanging a string should not take more than
about 10 ms). The main criterion is reliability.

?Reliability? means little risk of creating problems, little
risk of failure at run-time. (It might help when the client
[=Java process] can reset the communication to a known and
sane start state in case of problems detected at run-time.)

The host OS is Windows, but a portable solution won't hurt.

A list of possibilities I am aware of now:

Pipes

I have no experience with this. I heard one can establish
a new process ?proc? with ?exec? and then use

BufferedWriter out = new BufferedWriter(new
OutputStreamWriter(proc.getOutputStream()));
BufferedReader in = new BufferedReader(new
InputStreamReader(proc.getInputStream()));

A pipes is just 1:1 communication and only in 1 direction.

That type of pipe is bidirectional.

Well, that are actually two pipes aren't they? Or it's a socketpair,
depending on platform.

The Java Process supports in and out.

Whether the OS does it via single bidirectional or two unidirectional
does not change the Java code.

Thinking of it then two sounds more likely as Java also need to
separate err and out - that would be a lot easier with two.

Also, this approach only works if the Java
process always starts the other process.

Yep.

One process writes to the end of a file, the other reads
from the end of the file? - I never tried this, don't know
if it is guaranteed to work that one process can detect and
read, whether the other has just appended something to a file.

You can, but what do you do with the ever increasing file? This is not
reliable since the filesystem will fill up at some point.

It would be possible to switchover to a new file and
delete the old file if he really wanted to go this route.

Well, yes, but that soon gets nasty because of file locking etc.

Some coding required.

Arne