Connection between client and server Through websocket and vertx api - Java Discussion Boards

Actually I've done that too, that is why I added this in my question, and why I didn't asked only it's purpose:

Quote:
is there a way to stop the servlet from redirecting the user to another page? Even if you don't add a redirect or forward to the servlet, it will still redirect the user to it's map url.

A servlet is merely a program: it does what the code tells it to do. If you have a specific code problem then I would suggest opening a question with the details.

A HTTP servlet services HTTP requests, and it must finish the processing by sending a valid HTTP response to the client. The response doesn't need to be a redirect.

I need a human understandable definition of how java script interprets. It seems to be a dance between html pages and forms, and .js Files. I have 40 years experience in coding in 'C' and 'CPP'. The syntax of java is indeed similar. This language provides apparently no type info of any kind. params, indeed the whole of js seems to be devoid of types.

Issues are the relation between the JS Code and the pages using it That is totally unclear. Next, how do I debug Javascript. How do I set breakpoints? what software should use to code in Javascript.

Help Please!

Bram

Bram van Kampen

Well this is the Java forum, the Javascript one is at JavaScript Discussion Boards[^].

As Richard has pointed out - you'll get better answers in the right forum.
In the meantime - this article might help with the whole "how does it work" question How does JavaScript work and how can I build simple calculators with it? | HowStuffWorks[^]
There are further links in that article to other interesting "stuff" to help you in your research.
Note that I'm not actually advocating the how stuff works site per se, but you can pick up useful terminology that makes google searches more focussed.

 Hi, I have two files one - client side in Java script, the other in Java - server side ..
I can not send and receive messages What is the problem? Thanks

Js:

<!doctype html>

<html>
    <head>
        <meta charset = "utf-8">
        <title> Wiki Project </title>
        <script type = "text/javascript">
            window.addEventListener("load", onLoad, false);
           
            function onLoad()
            {
                var ws_address = "ws://0.0.0.0:8090"; 
                var socket = new WebSocket(ws_address);
                                
                socket.onopen = function(event) {onOpen(event);};
                socket.onclose = function(event) {onClose(event);};
                socket.onmessage = function(event) {onMessage(event);};
            }
            
            function onOpen(event)
            {
                alert("OPEN Connection");
            }   
            
            function onClose(event)
            {
                alert("CLOSE Connection");
            }
            
            function onMessage(event)
            {     
                alert(event.data.toString()); 
            }      
            
            function insertMessage()
            {      
                socket.send(document.directing.message.value);
                document.directing.message.value = "";
            }      
            
            function viewMessages()
            {            
                socket.send("@View@");  
            }         

            function deleteMessage()
            {         
                socket.send("@Delete@");
            }   
        </script>
    </head>
  
    <body> 
        <form name = "directing" method = "post" action = "javascript:;"> 
          Write a message: 
          <input type = "text" name = "message" size = "50" maxlength = "50" />
          <input type = "button" name = "add_message" value = "Add to server" onclick = "insertMessage()" />
          <input type = "button" name = "view_messages" value = "view messages from server" onclick = "viewMessages()" />
          <input type = "button" name = "delete_message" value = "delete message from server" onclick = "deleteMessage()" />          
        </form>   
    </body>
</html>

Java:

package com.mycompany.wiki_project;

import io.vertx.core.Vertx;

class VertxServer
{            
    private static int    place;
    private static String store_in_server[];
    private static String message_from_client;
    
    public static void main(String args[])
    {   
        place = 0;
        store_in_server = new String[50];
        
        Vertx vertx = Vertx.vertx();
                
        vertx.createHttpServer()
             .websocketHandler(ws -> ws.handler(ws::writeBinaryMessage))
             .requestHandler(req ->
             {
                 req.handler(buffer -> 
                 {
                    message_from_client = buffer.getString(0, buffer.length());
                    
                    switch (message_from_client)
                    {
                        case "@View@":
                            for (int i=0; i < place; i++)
                                req.response().write(store_in_server[i]);
                            break;
                        
                        case "@Delete@":
                            place--;
                            break;
                        
                        default:
                            store_in_server[place] = message_from_client + "\n";
                            place++;
                            break;
                    }  
    
                  });          
             }).listen(8090);
    }
}

You are trying to send to an invalid address.

How do I write this?
I need them both to listen to Port 8090

The port number is fine, but you are using the IP address 0.0.0.0.

i use

var ws_address = "ws://" + document.location.host + document.location.pathname + ":8089";

not work

Try connecting to the server code through a browser to see if it will accept a normal request. I do not know Vertx so you may need to use their support lines for help.

I just started to learn Java Servlet, but I can't really make it work.
I'm trying to do something basic first, to see how it works, read data from a form, print the 2 values to in the console and then redirect the user to another page.
Using the following code (what I though it will do it), redirects me to another page that doesn't exist "/Testare?firstName=Example+First&lastName=Example+Last"
I'm using Apache Tomcat for server.

The form is on Home.html:

<form action="Testare" method="GET">
    First name:<br> <input type="text" name="firstName"><br>
    Last name:<br> <input type="text" name="lastName"><br>
    <br> <input type="submit" value="Submit">
</form>

Testare servlet doGet trying to print and then redirect to "Test.html":

System.out.println("First name: " + request.getParameter("firstName") + "\nLast name: "
        + request.getParameter("lastName"));
response.sendRedirect("Test.html");

Your question isn't clear.

If the redirect page doesn't exist then it isn't going to work regardless of what you do.
If the initial page doesn't exist (it is not serviced) then it will not work regardless of whether the second page exists or not.

Redirection is handled by the browser not the server.

Here is an example which should have a working redirect.

Login and register form in one page in servlet[^]

I'm not entirely sure, but I think the problem was from web.xml. Now the problem is gone.

I am looking for the sample code which helps me to read the raw bytes from wireless modem connect via the USB port of a laptop and test it on IntelliJ.
Suggestion on this will be a great help.

Google is the place to search for sample code. And as it is a hardware device you may find something is already provided by the manufacturer.

Thanks, I am searching on google also but can you give some theoretical description about to read the Raw data in HEX form by using java code?

I am working on a project in which I am trying to create the software which sends the data on google sheets.

Sorry, but I have no idea how this device works so it is impossible to give a suggested answer. As I said you should check what supporting software is provided by the manufacturer.

This device is connected with FTDI32 chip and being new in this I just want to read the values either in decimal or Hexadecimal format only?
I hope you might help to give some useful code to work with it?

Sorry, I know nothing about that chip either. You really need to talk to the device manufacturer.

1. Find an API. Ideally one for the modem, but if not one for USB devices.
2. Figure out the protocol for the modem. You can't 'read' anything until you establish a connection.
3. Write code to use 1 and 2.
4. Find something to connect to.

This is NOT how you should learn to use IntelliJ however. Find something easier to start with.

I have a problem for RUN this code please help(Im working in Eclipse and i dont get any 'error report' but not works) (I dont know what i need any interface,abstract or method or something like that pls copy paste this code in your eclipse and help me ty )

package PaketX;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import javax.swing.JPanel;
@SuppressWarnings("serial")
class P06 extends JPanel implements ComponentListener {
	int width = 800, height = 600;
	Color AtaRasgeleRenk() {
		int r = (int)(256*Math.random());
        int g = (int)(256*Math.random());
        int b = (int)(256*Math.random());
        return new Color(r,g,b);
	}
	public P06() {
		setPreferredSize(new Dimension(width, height));
		addComponentListener(this);
	}
	@Override
	public void paintComponent(Graphics g) {
		super.paintComponent(g);
		int i, j, m = 7, n = 9;
		int x, w = Math.round((float)width/n);
		int y, h = Math.round((float)height/m);
		for(i = 0; i < n; i++) {
			x = i*w;
			for(j = 0; j < m; j++) {
				y = j*h;
				g.setColor(AtaRasgeleRenk());
				g.fillRect(x, y, w, h);
			}
		}
	}
	@Override
	public void componentResized(ComponentEvent e) {
		width = getWidth();
		height = getHeight();
	}
	@Override
	public void componentHidden(ComponentEvent e) {}
	@Override
	public void componentMoved(ComponentEvent e) {}
	@Override
	public void componentShown(ComponentEvent e) {}
}

If you had compiled this manually and tried to run it you would see that you have not defined a main method, so the program cannot be started. There are other parts missing also. Please see Trail: Creating a GUI With JFC/Swing (The Java™ Tutorials)[^].