Read flag synchronously from the PLC

In this sample program the value in flag double word 0 in the PLC is read and displayed:

Unpack the sample program 'Read flag synchronously from PLC': sample07.zip

• To execute the *.jar sample, the command 'java -classpath "Sample07.jar;[path to TcJavaToAds.jar] Main' must be executed in the console in the correct directory (example path: "C:TwinCAT\Ads Api\AdsToJava\*"). For this, java must be entered in the environment variables.

import de.beckhoff.jni.JNIByteBuffer;
import de.beckhoff.jni.tcads.AdsCallDllFunction;
import de.beckhoff.jni.tcads.AmsAddr;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;

public class Main {
    public static void main(String[] args) {
    try{
        long err;
        AmsAddr addr = new AmsAddr();
        JNIByteBuffer buff = new JNIByteBuffer(Integer.SIZE / Byte.SIZE);
        ByteBuffer bb = ByteBuffer.allocate(0);

        // Open communication        
        AdsCallDllFunction.adsPortOpen();
        err = AdsCallDllFunction.getLocalAddress(addr);
        addr.setPort(AdsCallDllFunction.AMSPORT_R0_PLC_RTS1);

        if (err != 0) {
        System.out.println("Error: Open communication: 0x"
            + Long.toHexString(err));
        } else {
        System.out.println("Success: Open communication!");
        } 

        // Specify IndexGroup, IndexOffset and read PLCVar
        err = AdsCallDllFunction.adsSyncReadReq(addr,
                        0x4020,     // Index Group
                        0x0,    // Index Offset
                        buff.getUsedBytesCount(),
                        buff);
        if (err != 0) {
        System.out.println("Error: Read by adress: 0x" 
            + Long.toHexString(err));
        } else {
        bb = ByteBuffer.wrap(buff.getByteArray());
        bb.order(ByteOrder.LITTLE_ENDIAN);

        System.out.println("" + bb.getInt());
        }

        // Close communication
        err = AdsCallDllFunction.adsPortClose();
        if(err!=0) { 
        System.out.println("Error: Close Communication: 0x" 
            + Long.toHexString(err)); 
        }

        System.out.println("Press enter to continue..");
        System.in.read();
    }
    catch (Exception ex){
        System.out.println(ex.getMessage());
    }
    }
}