Re: Interplatform (interprocess, interlanguage) communication
On 02/03/2012 08:52 PM, Stefan Ram wrote:
=BBX=AB 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.
=BBReliability=AB 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 =BBproc=AB with =BBexec=AB 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.
Files
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.
What if the processes run very long and the files get too
large? But OTOH this is very transparent, which makes it easy
to debug, since one can open the files and directly inspect
them, or even append commands manually with =BBcopy con file=AB.
Sockets
This is slightly less transparent than files, but has the
advantage that it becomes very easy to have the two
processes running on different computers later, if this
should ever be required. Debugging should be possible
by a man-in-the-middle proxy that prints all information
it sees or by connecting to the server with a terminal.
You can as well use a packet sniffer (Wireshark for example). If you
use a standard protocol you'll typically have encoding functionality in
the tool.
JNI
JNI might be used to access code written in C or
ABI-compatible languages. This should be fast, but I heard
that it is error prone to write JNI code and needs some
learning (code less maintainable)?
That would be a clumsy approach IMHO.
I'd pick a higher level protocol such as
- SOAP (XML based, ubiquitous)
- CORBA (a little out of fashion but quite efficient in terms of network =
transport)
Advantage: you can focus on definition of the API and need not take care =
of all the nifty details. Choice should also depend on the availability =
for language X, of course.
Kind regards
robert