Tag: java

Java Modbus Client

Modbus TCP Client Example

public class run {
	public static void main(String[] args)
	{
		ModbusClient modbusClient = new ModbusClient("127.0.0.1",502);
		try
		{
			modbusClient.Connect();
			modbusClient.WriteSingleCoil(0, true);
			modbusClient.WriteSingleRegister(0, 1234);
			modbusClient.WriteMultipleRegisters(11, ModbusClient.ConvertFloatToTwoRegisters((float) 123.56));
			System.out.println(modbusClient.ReadCoils(0, 1)[0]);
			System.out.println(modbusClient.ReadHoldingRegisters(0, 1)[0]);
			System.out.println(ModbusClient.ConvertRegistersToFloat(modbusClient.ReadHoldingRegisters(11, 2)));
		}
		catch (Exception e)
		{		
		}	
	}
}

Read an Write 32 Bit Values

    public static void main(String[] args) 
    {
        ModbusClient modbusClient = new ModbusClient("127.0.0.1", 1536);
        try
        {
            modbusClient.Connect();
            //Write Float value to Register 10 and 11
            modbusClient.WriteMultipleRegisters(9, ModbusClient.ConvertFloatToTwoRegisters((float)(1323.55)));
            //Write 32 bit value to Register 12 and 13
            modbusClient.WriteMultipleRegisters(11, ModbusClient.ConvertDoubleToTwoRegisters((1323554)));
            //Read Float Value from Register 10 and 11
            System.out.println(ModbusClient.ConvertRegistersToFloat(modbusClient.ReadHoldingRegisters(9, 2)));
            //Read 32 Bit Value from Register 12 and 13
            System.out.println(ModbusClient.ConvertRegistersToDouble(modbusClient.ReadHoldingRegisters(11, 2)));
        }
        catch (Exception e)
        {
        System.out.println(e.toString());
        }   
    }

References
https://www.youtube.com/user/emileackbarali/videos
https://www.udemy.com/the-1-hour-modbus-rs485-primer/
https://www.rtaautomation.com/technologies/modbus-rtu/
http://easymodbustcp.net/java-modbus-tcp-client-example
http://easymodbustcp.net/java-read-an-write-32-bit-values
https://en.wikipedia.org/wiki/Modbus

Modify Socket parameters of Mqtt Client

import java.io.IOException;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;
import java.net.SocketException;
import java.net.UnknownHostException;

import javax.net.SocketFactory;

public class MySocketFactory extends SocketFactory {

    private SocketFactory socketFactory;
    private Socket socket;

    public MySocketFactory() {
        this.socketFactory = SocketFactory.getDefault();
    }

    public MySocketFactory(SocketFactory socketFactory) {
        this.socketFactory = socketFactory;
    }

    @Override
    public Socket createSocket(String host, int port) throws IOException {
        socket = this.socketFactory.createSocket(host, port);
        modifySocket();
        return socket;
    }

    @Override
    public Socket createSocket(String host, int port, InetAddress localHost, int localPort) throws IOException {
        socket = socketFactory.createSocket(host, port, localHost, localPort);
        modifySocket();
        return socket;
    }

    @Override
    public Socket createSocket(InetAddress host, int port) throws IOException {
        socket = socketFactory.createSocket(host, port);
        modifySocket();
        return socket;
    }

    @Override
    public Socket createSocket(InetAddress address, int port, InetAddress localAddress, int localPort) throws IOException {
        socket = socketFactory.createSocket(address, port, localAddress, localPort);
        modifySocket();
        return socket;
    }

    @Override
    public Socket createSocket() throws IOException {
        socket = socketFactory.createSocket();
        modifySocket();
        return socket;
    }

    private void modifySocket() throws IOException {
        socket.setKeepAlive(true);
        socket.setSoTimeout(10 * 1000);
        socket.setSoLinger(true, 0);
        socket.setTcpNoDelay(true);
    }
}
String broker = Statics.broker;
// mqtt paho client id
clientId = MqttClient.generateClientId();
client = new MqttAndroidClient(MyMqttService.this, broker,
                        clientId, new MemoryPersistence());

MqttConnectOptions options = new MqttConnectOptions();
options.setAutomaticReconnect(false);
options.setCleanSession(true);
options.setUserName(""test");
options.setPassword("test".toCharArray());
options.setConnectionTimeout(20);
options.setKeepAliveInterval(0);

MySocketFactory mySocketFactory=new MySocketFactory();
options.setSocketFactory(mySocketFactory);

Sort a list of objects by a certain value within the object

Collections.sort(myList, new Comparator<EmployeeClass>(){
    public int compare(EmployeeClass obj1, EmployeeClass obj2) {
        // ## Ascending order
        return obj1.firstName.compareToIgnoreCase(obj2.firstName); // To compare string values
        // return Integer.valueOf(obj1.empId).compareTo(obj2.empId); // To compare integer values

        // ## Descending order
        // return obj2.firstName.compareToIgnoreCase(obj1.firstName); // To compare string values
        // return Integer.valueOf(obj2.empId).compareTo(obj1.empId); // To compare integer values
        }
    });
responseDto.getValues().sort((o1, o2) -> o1.getTime().compareTo(o2.getTime()));
responseDto.getValues().sort(Comparator.comparing(ItemTableResponseDto.Value::getTime));

References
https://stackoverflow.com/questions/9109890/android-java-how-to-sort-a-list-of-objects-by-a-certain-value-within-the-object

Detect Outlier values in Java Using BoxPlot formula and Apache Commons Math Library

public boolean isOutlier(List<RawItem> rawItems, String value) {

        DescriptiveStatistics descriptiveStatistics = new DescriptiveStatistics();
        double dValue = Double.parseDouble(value);

        for (RawItem rawItem : rawItems) {
            double d = Double.parseDouble(rawItem.getValue());

            descriptiveStatistics.addValue(d);
        }

        double Q1 = descriptiveStatistics.getPercentile(25);
        double Q3 = descriptiveStatistics.getPercentile(75);
        double IQR = Q3 - Q1;

        double highRange = Q3 + 3 * IQR;
        double lowRange = Q1 - 3 * IQR;

        if (dValue > highRange || dValue < lowRange) {
            return true;
        }

        return true;
    }

References
https://www.shmoop.com/basic-statistics-probability/box-whisker-plots.html
http://www.baeldung.com/apache-commons-math
https://stackoverflow.com/questions/22888902/get-median-from-number-series-using-apache-commons-math

Guide to Guava’s EventBus in Java

Setup

EventBus eventBus = new EventBus();

Creating Listeners

public class EventListener {
 
    private static int eventsHandled;
 
    @Subscribe
    public void stringEvent(String event) {
        eventsHandled++;
    }
}

Registering Listeners

EventListener listener = new EventListener();
eventBus.register(listener);

Unregistering Listeners

eventBus.unregister(listener);

Posting Events

@Test
public void givenStringEvent_whenEventHandled_thenSuccess() {
    eventBus.post("String Event");
    assertEquals(1, listener.getEventsHandled());
}

Posting Custom Events

public class CustomEvent {
    private String action;
 
    // standard getters/setters and constructors
}
@Subscribe
public void someCustomEvent(CustomEvent customEvent) {
    eventsHandled++;
}
@Test
public void givenCustomEvent_whenEventHandled_thenSuccess() {
    CustomEvent customEvent = new CustomEvent("Custom Event");
    eventBus.post(customEvent);
 
    assertEquals(1, listener.getEventsHandled());
}

Handling an Unsubscribed Event

@Subscribe
public void handleDeadEvent(DeadEvent deadEvent) {
    eventsHandled++;
}

References
http://www.baeldung.com/guava-eventbus

Install Apache Tomcat 8 on Ubuntu 16.04

Install Java

Create Tomcat User

sudo groupadd tomcat
sudo useradd -s /bin/false -g tomcat -d /opt/tomcat tomcat

Install Tomcat

sudo mkdir /opt/tomcat
wget http://apache.mirrors.ionfish.org/tomcat/tomcat-8/v8.5.5/bin/apache-tomcat-8.5.5.tar.gz

Update Permissions

cd /opt/tomcat
sudo chgrp -R tomcat /opt/tomcat
sudo chmod -R g+r conf
sudo chmod g+x conf
sudo chown -R tomcat webapps/ work/ temp/ logs/

Create a systemd Service File

sudo update-java-alternatives -l
Output
java-1.8.0-openjdk-amd64       1081       /usr/lib/jvm/java-1.8.0-openjdk-amd64
sudo nano /etc/systemd/system/tomcat.service
[Unit]
Description=Apache Tomcat Web Application Container
After=network.target

[Service]
Type=forking

Environment=JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-amd64/jre
Environment=CATALINA_PID=/opt/tomcat/temp/tomcat.pid
Environment=CATALINA_HOME=/opt/tomcat
Environment=CATALINA_BASE=/opt/tomcat
Environment='CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC'
Environment='JAVA_OPTS=-Djava.awt.headless=true -Djava.security.egd=file:/dev/./urandom'

ExecStart=/opt/tomcat/bin/startup.sh
ExecStop=/opt/tomcat/bin/shutdown.sh

User=tomcat
Group=tomcat
UMask=0007
RestartSec=10
Restart=always

[Install]
WantedBy=multi-user.target
sudo systemctl daemon-reload
sudo systemctl start tomcat
sudo systemctl status tomcat

Configure Tomcat Web Management Interface

sudo nano /opt/tomcat/conf/tomcat-users.xml
<tomcat-users . . .>
    <user username="admin" password="password" roles="manager-gui,admin-gui"/>
</tomcat-users>

For the Manager app, type:

sudo nano /opt/tomcat/webapps/manager/META-INF/context.xml

For the Host Manager app, type:

sudo nano /opt/tomcat/webapps/host-manager/META-INF/context.xml
<Context antiResourceLocking="false" privileged="true" >
  <!--<Valve className="org.apache.catalina.valves.RemoteAddrValve"
         allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" />-->
</Context>
sudo systemctl restart tomcat

Access the Web Interface

http://server_domain_or_IP:8080

References
https://www.digitalocean.com/community/tutorials/how-to-install-apache-tomcat-8-on-ubuntu-16-04