[Visual-devel] Re: plc controling and monitoring [av ok]

[Thomas H. <Tho...@we...>]

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Von:      "Demeter Robert" <rde...@ma...>
Gesendet: 01.07.04 15:29:27
An:       "Thomas Hergenhahn" <Tho...@we...>
Betreff:  Re: plc controling and monitoring [av ok]


=20
>public=20
>synchronized=20
>void getValTab() {=20
=20
>    if (wasModified){
 >       System.out.println(get("savesettings",""));
 >
 >       wasModified=3Dfalse;
 >
 >   } =20
I do not see at the first glance what you did modify. The command "saveset=
tings" causes the server to save the values of all cells modified into a f=
ile n.set where n is the number of the spreadsheet. This is needed to save=
 setpoints modified by a user over restarts of VISUAL. If the applet "cras=
hed" in this point, can the following suspection be true:
The server has not the rights to write into the working directory or has n=
ot the rights to overwrite n.set. If this would be the case, it may be tha=
t the server thread is either halted or dies. I will check this situation.=

If the server is only halted, you should see the widgets change from norma=
l display to displaying "Host!" in white on red background telling "we can=
not get a value from the host".
A reload causes your browser to newly connect to the server=B4s accepter thr=
ead which will spawn a new server child thread.
If your widgets did not show the error message, this may be due to imprope=
r using of threads in the JAVA applet. I will check this too.
=20
>Now, it's works fine. I can read PLC inputs, outputs and markers, and i c=
an write markers of PLC from web >interface. It's a great work. It is look=
 like one OPC server that cost more than 600$.
Thank you. I also hope it is far less complicated than OPC.
=20
>Do you have a PPI specification or protocol description=3F I use serial mon=
itor, noDaveLib driver and other >tools to find out the protocol functions=
. =20
No, I havn=B4t. AFAIK, you can get it from Siemens for money, but you have t=
o sign some licence about it=B4s usage, excluding usage for open source proj=
ects.
=20
>Do you know another technology (methology) to interact with PLC from web =
interface (another HMI tool) or >another free tool=3F=3F=20
I have JAVA classes to directly interact with the serial interface and PPI=
-Adapter, but handling serial connections from JAVA is no fun. I do not co=
nsider them ready right now. Serial connection is also not possible from a=
n applet with the normal JAVA security settings. It is also nosensical to =
deliver an applet to a client that is not itself directly connected to the=
 PLC.

I also have JAVA classes to directly interact with the CPs 243 or 343/443 =
over Ethernet. The drawbacks are:
-The number of clients is very limited (4=3F).=20
- The PLC=B4s communication load increases with number of clients.
- Other than Siemens Applets distributed with the -IT CPs, the connection =
cannot be tunneled over HTTP, hence will not work over firewalls, if port =
102 is not explicitly allowed.

Thomas
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