GMM50 said:
It appears the using the serial port will require that special piece
of code (a dll) on the users machine. That's OK for development and
the earlier users of this project.
As you know by now, Java doesn't have built-in serial port support, and
there are issues with the various standard packages: SimpleSerial is the
simplest, but its slow: it was designed to support byte at a time comms
with a PIC microchip. Neither it or the Sun package are very current and
RXTX looks complex to install. I looked at them all and decided that
writing my own looked to be less problematic.
You're right about needing specialized code. Serial ports are simple to
handle under some OSen, e.g. Linux, any other *NIX, or Microware's OS9,
but quite hard under DOS or Windows.
A while back I needed to talk to a Parallax STAMP from C. I was using a
Borland compiler. Neither its standard libraries nor DOS/Windows
supplied any serial port support worth a damn and I couldn't find any
usable OSS code on the 'net. I ended up buying a copy of Willies
Software's COMM/DRV package, which "just worked". If you do have to talk
to serial ports on a DOS/Windows box this product is worth a look no
matter what you end up putting behind it.
And My hope is that the Ethernet interface will not require any of
that special code.
If your devices have built-in TCP/IP support then it should be easy to
handle them because Java's TCP/IP support is good and fairly easy to
use, especially if you've used sockets or datagrams in C.
Otherwise, you're going to end up building some sort of non-Java
interface. I think the options are:
1)to build something that's likely to look remarkably like my
SerialPort server and talk to it over TCP/IP. Done right,
this code can be application independent: effectively just
a byte pipe that any application can use to talk to any device
plugged onto a serial port.
2)use JINI to let Java talk directly to a lump of C that drives
the ports. I think this would require the application to live
on the same box as the serial ports - either that or you ending up
writing another serial server, but this time in Java.
3)as (1) but use a small, dedicated interface box that runs the server
and nothing else. Plug it onto your LAN where Java can find it.
It could run under the OS of your choice, would be small and low
powered and would allow the control software to be installed on any
other host(s) that can see it.
If you go for (3) the support hardware could be anything from a Beck
IPC@CHIP PC-on-a-chip or a Gumstix mini board upwards. The next step up
would be small form factor kit like NorhTec's MicroClient Jr, the Sumo
ST166 or systems based on mini-ITX boards. Many of these come with
minimal Linux distros as a standard option, so that would solve the
serial hardware interfacing problem. Or, or course, you could use a
regular PC with its backplane crammed with serial ports.
I've used Visual C, Visual Basic and C++ Builder. They all stumble
when you need to install on users machines and support is difficult.
It seems to me that using a dedicated interface box to handle the serial
ports is worth a close look. The benefit is that all the specialized
support libraries, etc only exist on the interface box. All applications
can be written in Java or whatever seems sensible and don't need
anything (except possibly an interface class) to connect to it: they
certainly don't need to know what's running in it.
If you use Java for the applications then they can even be installed
automatically on user's systems if you use Web Start to deploy them.
HTH
