1. TwinCAT ADS-DLL Java
2. TcJavaToAds
3. Delete a handle of a PLC variable

Delete a handle of a PLC variable

This Sample shows how to delete a handle of a PLC variable:

import de.beckhoff.jni.Convert;
import de.beckhoff.jni.JNIByteBuffer;
import de.beckhoff.jni.tcads.AdsCallDllFunction;
import de.beckhoff.jni.tcads.AmsAddr;

public class Main {
 public static void main(String[] args) {
    long err;
    AmsAddr addr = new AmsAddr();
    JNIByteBuffer symBuff;
    JNIByteBuffer handleBuff = new JNIByteBuffer(Integer.SIZE / Byte.SIZE);

    try {
     // Open communication     
     AdsCallDllFunction.adsPortOpen();
     err = AdsCallDllFunction.getLocalAddress(addr);
     addr.setPort(851);

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

     // Convert Symbol name to byte buffer
     symBuff = new JNIByteBuffer(PLC_VAR.getBytes());

     // Get handle via symbol name
     err = AdsCallDllFunction.adsSyncReadWriteReq(addr,
         AdsCallDllFunction.ADSIGRP_SYM_HNDBYNAME,
         0,
         handleBuff.getUsedBytesCount(),
         handleBuff,         //buffer for getting handle
         symBuff.getUsedBytesCount(),
         symBuff);         //buffer containg symbol name
     
     if(err!=0) { 
        System.out.println("Error: Get Handle: 0x" + Long.toHexString(err)); 
     } else {
        System.out.println("Success: Get Handle!");
     }
     
     // Release handle
     err = AdsCallDllFunction.adsSyncWriteReq(addr,
         AdsCallDllFunction.ADSIGRP_SYM_RELEASEHND,
         0,
         handleBuff.getUsedBytesCount(),
         handleBuff);
     
     if(err!=0) {
        System.out.println("Error: Release Handle: 0x"
                + Long.toHexString(err));
     } else {
        System.out.println("Success: Handle removed!");
     }

     // 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());
    }
 }
}
 

Unpack the example program 'Delete a handle of a PLC variable'

To be able to execute the *.jar sample you need to run 'java -classpath "Sample08.jar;[Path to TcJavaToAds.jar] Main' from the console (path might be "C:TwinCAT\Ads Api\AdsToJava\*"). Make sure the current path is correct and you have added java to your environment variables.