Java

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;
import java.net.UnknownHostException;

public class Requester {
Socket requestSocket;
ObjectOutputStream out;
ObjectInputStream in;
String message;

Requester() {
}

void run() throws IOException {
    try {
        // 1. creating a socket to connect to the server
        requestSocket = new Socket("192.168.0.19", 4370);
        System.out.println("Connected to given host in port 4370");
        // 2. get Input and Output streams
        in = new ObjectInputStream(requestSocket.getInputStream());
        // 3: Communicating with the server
        String line;
        while (true) {
            line = in.readLine();
            if (line != null) {
                System.out.println(line);
            }
        }
    } catch (UnknownHostException unknownHost) {
        System.err.println("You are trying to connect to an unknown host!");

    } catch (IOException ioException) {
        ioException.printStackTrace();

    } catch (Exception Exception) {
        Exception.printStackTrace();

    } finally {
        in.close();
        requestSocket.close();
    }
}

void sendMessage(String msg) {
    try {
        out.writeObject(msg);
        out.flush();
        System.out.println("client: " + msg);

    } catch (IOException ioException) {
        ioException.printStackTrace();
    }
}

public static void main(String args[]) throws IOException {
    Requester client = new Requester();
    client.run();
}
}

public class ChildThread implements Runnable{
    //variable-declaration

    public ChildThread(){
    //initialization
    }

    public void run(){
    //some code here;
    }

    public void doMethod(){
    //do something
    }
}


Now I'm creating multiple ChildThread in AnotherClass

public class Parent {
    Thread t;
    //variables

    public Parent(){
    //initialization
    }

    //statements

    private someParentMethod{
        //for some event1
        t=new Thread(new ChildThread(),"name1");
        t.start();
    }

    private doSomething(){
        //some event1 for name1
        //want to call doMethod() of ClildThread name1
    }
}

try {
    (new Thread(new Lettore(port), "Lettore")).start();
} catch (Exception e) {
    System.err.println("Errore " + e);
}

    SerialPort port;

    public Lettore(SerialPort port) throws IOException {
        this.port = port;
    }

    @Override
    public void run() {
        byte[] buffer = new byte[1024];
        int len = -1;
            try {
            while (true) {
                //read, write on terminal, echo.
                len = port.getInputStream().read(buffer);
                System.out.print(new String(buffer, 0, len));
                if (len != 0) {
                    port.getOutputStream().write(buffer, 0, len);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}