Internet PLC Forum

Hi,

I'm having a bit of trouble trying to program some jave/html using a couple of FMD's. I realise this is primarily a plc programming site but hopefully someone can give me a hint.

I have 2 PLC's, plc1 and plc1. Plc1 is acting as a web server and plc2 for data collection. It has to be this way.

The problem is when browsing to plc1 and having that web page try to get data from plc2, using XMLHttpRequest and host link protocol format, I'm getting the CORS request failed, found using Firefox and Firebug.

It appears from reading that the web server needs to have "Access-Control-Allow-Origin:" appended to it's html header and I gather this doesn't occur.

Can anyone help in this area?

cheers,

john

Hi,

I'm assuming here that you want to connect over the LAN and not RS485.

Firstly you need to connect to the plc you want to write to/read from. The following command will do that:

PRINT #4 "<MBTCPCONNECT 192.168.0.40:502>"

The 192.168.0.40 IP address is the one for the destination plc. The 502 at the end is necessary as it is the port number that is used by MODBUS over tcp/ip

Next, write to a location on the destination plc use the following command:

WRITEMODBUS 4,1,1101,DM[50]

In this instance I am writing to an DM location on the destination PLC from a DM location on the source PLC. How do I know the destination is a DM location? It is the 1000 at the beginning of the 1101 (check chapter 14, pg 10 of the manual). I am actually writing to DM[100] on the destination PLC, you can read the manual to see how the numbers work out.
The 4 at the beginning is the port I'm going out on the source, 4 because I'm using the ethernet socket. The following 1 is the Id of the destination plc, seems redundant but necessary
The DM[50] is the location of the data on the source plc.

Hopefully this makes some sort of sense. It will be very similar for RS485.

cheers,

john