How To Receive Some Data From Multiple Clients On Network
Apr 16, 2014
I got my first project in which i need to receive some data from multiple client on network regularly(say every second) and then process that data and stored it to the database and then GUI needs to be created which display data accordingly.
While thinking for the design i thought blocking queue to implement the same. Like producer receive data from the port into a string builder and put that into the LinkedBlockingQueue. Consumer will take this data , process some work on it and store it into the database.I am using sybase ase 15 as a database.
My question is as i am receiving data very frequently which require insertion , updation and search almost every second into the database. What is the best way to improve the performance.
say i have 2 types of data is coming one having keyword 'Alarm' and other having 'ceased' so i need to use something like this
common fields in both is name and number.
if (ceased)
search into the database for particular event for which this ceased receive using name and numbe rand update the another field into it Also make separate entry for it
else
make a entry
Also as i am using 2-3 thread for consumers and thread = Number of client for the producer. So i thought to use synchronization at the consumer side which writes data into the database such that only 1 thread can write it.
I would like to understand how does multipart/form-data works during file upload scenario's, Does it chunks the data from client to server while transferring the files ?
I haven't been able to find a cut and paste working example of how to receive MIDI data from a MIDI device, like my piano, and display something to System.out.There are all sorts of examples for synthesizers, sequencers and sending data to a MIDI device, but I have not been able to find a single example of how to receive MIDI data and just display a simple message.
I just need something simple that works to start playing with it, and understanding how it works. Having a working example would also support understanding the Sound API descriptions. They read like differential equations texts books to me, i.e. not clear at all.
I have a working example of how to poll all devices and getDevice.info, which is supposed to then be used to address a specific MIDI device.
I've also looked at a number of books, in the store and on line.I haven't seen a single example anywhere.the closest I found to working examples was on StackOverflow, but I didn't understand some of the other code in the examples, which may or may not have been working correctly anyway.
I'm using netbeans to develop an application to send and receive data via RS 232 standard. I can send data but I can't read it.what can I do? I have this message in the console: Underlying input stream returned zero bytes. (I must use also threads to have application in real time but I don't understand very well....
I have made a server/multi Clients where Clients send Double data but my problem is that the clients send this data to Server only wonce, and the server waits again the connection from client. (I have to run the clients manually each time)what i'm looking: the client should always send data to server. like an infinite loop.
I was tasked to do a 2-4 player network card game. Before I jumped into doing the card game. I decided to try out an a simple program which is the clients taking turns to type in their textfield.
I have a server that listens to 3 incoming client connections. once all 3 clients is being connected,
Steps
1) The first client will send the message first while the second and third client will wait for the first client to finish sending.
2) After the first client finished sending the message, it will be second client turn to send the message and the third client will wait for the second client to send finish.
3) After the third client finished sending the message, it will be third client turn to send the message and the first client will wait for the third client to send finish and (go back to step 1))
**The first client can only start typing once all 3 clients is being connected**
In my server class,I spawn a new Thread once a client is connected, I do a wait() on each time the client is being connected, I stored the thread in a arraylist as well. I have an id to keep track how many clients is currently connected. once the id reaches 3, I used notifyall() to notify all the threads and set the first position of my arraylist as my currentThread so that I can keep track which is the currentThread running.
I started 3 clients. and I typed the textfield of the first client but my server isn't receiving any messages.
class Server implements Runnable { private List<SpawnNewThread> sntList = new ArrayList<SpawnNewThread>(); private SpawnNewThread currentThread; private int id = 0;
I'm trying to create a server which sends the clients connected to it its local time. Looking at a few tutorials I've managed to connect the clients to the server, but can't send data to the clients. I've successfully done easier examples, without threading. I guess the problem might be im me not knowing what exceptions are for.
Client: When running the code "AAAAAAA" does execute but "BBBB" doesn't, so I guess the problem should be in fraseRecibida = entradaDesdeServidor.readLine();
import java.io.*; import java.net.*; import java.util.Scanner; public class Client { public static void main(String[] args) throws Exception{ String fraseRecibida;
[code]....
I don't understand the exceptions, maybe I should give them a look before continuing with sockets. Being frank I'm not really sure why the while(true) is there.
import java.io.*; import java.net.*; import java.util.Calendar; public class ServerThread extends Thread{ Socket socket; ServerThread(Socket socket){ this.socket = socket;
I've been asked to create an app for nutritionists to check what their clients are eating.
I've found a database of all foods with nutritional values. In the past I've dealt with databases which just have are just one dimensional, so it's been easy to just create a string array for it. But this is absolutely huge, it's got about 10,000 rows and 30 or so columns, so that's not going to work any more.
The app needs to ask what the client ate at which times, and then save this along with the nutritional values.
What would be the best way to go about storing and calling a database of this size in java?
Should I learn SQL and JDBC to tackle it or is there any easier way?
There are multiple .CSV files (each file has multiple rows and columns). I need to fetch data from all the files and find MEDIAN of the values for each column and do further calculations. Suppose there are 3 files, i need to find the MEDIAN of column 1 in file1, MEDIAN of column 1 in file2, MEDIAN of column 1 in file3. Below code just fetch data from one file.
I have declared an array list that will store data type of 1 Character and 2 integer. The data that will be store in this list is
1. A = {0 3} 2. B = {0 5} 3. C = {0 3} 4. D = {0 3} 5. E = {0 5} 6. F = {0 6}
Now here the alphabets are routers and integers are there con1 and con2 respectively. I have a set of router={ A,B,C,D,E,F}.
Step 1:I have to subtract con1 from con2 i.e. (3-0) of all the routers and Step 2: then put the router having largest value in new set 1 and Step 3: then this router will be subtract from the router set. Step 4:then again I have to repeat the step 1 until the value of routers become <= 1.
Now what I did is I defined 3 arrays first is String array that stores names of routers, 2nd array that stores the first value and 3rd array that stores the second value. I can find the largest value but how to store the name of router against the largest value in the set.
I am trying to create a Community Theater program that has Actors, Directors, Investors, Staff etc. I should eventually be able to input the information for the people from both a file and the keyboard. I'm working on trying to take in multiple Actors from one file and adding them to an ArrayList of Actors. My code takes in only one actor right now.
I am trying to take in multiple sets of data for the same type of class but creating new instances after each set of data (16 lines). Each actor has 16 lines of data (text file included), so I was thinking that I would need perhaps a for loop but I am unsure of how and where to implement it. I am also unsure about adding these new actors to the Actor ArrayList. I'm a little shaky on the idea of creating multiple objects when it is unknown how many you need to create. Right now, I know how many Actors I need to add but it would be nice if I could learn how to expand that based on the user's needs.
My Questions: How can I write my program to know when it is done reading 16 lines and then initialize a new Actor (will expand to other people)?(expanded below)Eventually, I plan on using my theaterObj (an instance of CommunityTheater class), what if I wanted to move the readActorFile method to that class? Would that change the way I implement anything majorly? Would it still be a static method? I ask this because I want the Actors array to be a variable in the CommunityTheater class. I would extend this to adding actors to an ArrayList in a Play class which would be in CommunityTheater as well. So, essentially a CommunityTheater has different Play(s), and each Play contains a list of Actors.
I don't exactly know where I should put a loop (should I use a loop?) to read through each line, in readActorFile or in readInFile? How should I write this loop, as in, how do tell my program what line it's reading?
for(countLine=0; countLine < 17; countLine++) or while(countLine<17) read all the info and then an if(?)-
if(file has a next line)-I don't really know how to code this-start over with loop of reading information?I don't know about the for loop, as I'm not sure how to "count" lines in a text file.OR I've been thinking that readInFile in the Actor class could return something(true/false?) to let the method readInActor know that it's done reading, then readInActor can check to see if there's anything else in the file, if there is- it would call the readInFile in Actor class again to read in information... and so on. But again I am unsure of how to code this.
I currently have a datatable on the bookingList.xhtml which is supposed to list all bookings made, if first booking petName is spot it displays the booking details perfect but if another booking is made (for example one with petName fluffy) then it displays 2 lines with fluffys details and spots details are not displayed, it carries on that if a third booking is made then the 3rd bookings details are displayed 3 times and neither spot or fluffys booking details are displayed,
bookingList.xhtml code <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:h="http://java.sun.com/jsf/html" xmlns:f="http://java.sun.com/jsf/core" xmlns:p="http://primefaces.org/ui">
I managed to retrieve data, and set data in my own ways in which I like. But my problem is, if the file does not contain anything (fully empty), when I try to use my
I have just taken it upon myself to attempt to develop an application using java that will implement several features for my aircraft maintenance unit. I've taken a few courses in Java and I am a computer science major, so I wanted to use this as a way to improve my coding skills while also improving the effectiveness of my unit.
Anyway my application needs to have these key features:
1. Access a recall roster that is in Excel format and read the names/phone numbers of up to 200 members. The application also needs to be able to update this information and save it.
2. The application also needs to be able to initiate a recall to some or all of the members on the recall roster via text message.
3. The application needs to be able to receive messages back and display them under each name from the recall roster.
My current plan is to set up a GUI that expands JButtons in a scrollable window as members are read in from the excel document. Upon clicking any of the buttons the person will be contacted individually via a custom message that can be typed in via a popup window after clicking it. Alternatively you can check a box next to any persons button to add them to the list of people to be contacted and then click a button that says "Contact those checked" or something along those lines. Finally there will be a button that just says initiate total recall and it will contact everyone.
As for the interface I want each button to be highlighted red until a response has been received from the person associated with that button, which will then be recorded under their contact information.
* A pop-up menu generates an array of rectangle objects; each rectangle having random x.y coords and colour. * The number of rectangles in the array is user selected from the popup list. * The APopUp class has a 'getter' method that returns the array. * The pop-up object is instantiated in an object of the AFrame class. * The AFrame object needs to get the array each time the popup changes its state.
The problem: . * As I see it, the AFrame object needs to informed of the pop-up's state of change event or does the problem lie in how I have decided which responsibilities each class is to have? I've tried to be as logical as possible during planning.
In the days of FORTRAN or BASIC we would hammer a solution through with brute force, but I would like to keep to Java's philosophy of encapsulation and clean interfaces and that it seems to has generated a impasse of brain warping proportions.
import java.awt.Frame; import java.awt.Label; import java.awt.event.ItemEvent; import java.awt.event.ItemListener; public class AFrame extends Frame implements ItemListener {
I'm using the JOptionPane to display and receive information to/from the user. In addition to this, I am using StringBuilder to receive inputs from the user and then manipulate (append) that input to display the desired output.
//Example
(JOptionPane): "Enter text" (user input): Java is cool! (program): *stringBuilder.append(" I love it!") JOptionPane.showMessageDialog( ); .....
Psuedo-like code. The problem is that showMessageDialog(null, string) and not showMessageDialog(string, string). I want to display the enter text: " Java is cool! I love it! " in the JOptionPane. How do I accomplish this, since showMessageDialog only accepts (null, string).
Receive input events from a MIDI interface device.
This has suddenly stopped working for me after years of using the Java MIDI software.
I have tested this on two different macbook pro's.
I have a variety of MIDI interfaces from different manufacturers. I can find the devices using MidiSystem.getMidiDevice. But I cannot get them to see any input MIDI events.
I can create events in code and send them to output devices and have them seen by those devices. It's just the input that seems to be broken.
I have tried using previously working software I having been developing for years and I have tried with a very simple test program.
I write a Client/Server program,trying to send and receive a object between client and server. I use the ObjectStream but there exists an EOFException on the client side when invoking readObject() .... I've tried many times but couldn't figure it out ...
server-side code
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { try{ ObjectOutputStream out = new ObjectOutputStream(resp.getOutputStream()); ObjectInputStream in = new ObjectInputStream(req.getInputStream()); PersonalData pe = (PersonalData)in.readObject(); System.out.println(pe.getYearlySalary());
I wanted to write a simple code that receives information from the user (double-digit number and above) and calculates it's numbers.
For instance- The user wrote a number- 234, the software will return the number 9 (2+3+4 = 9).
Tried to use a loop for that, but I got stuck since I didn't know what to write.
This is what I've wrote so far
Java Code:
import java.util.Scanner; public class Calculate { public static void main(String[] args) { System.out.println("Please type a number larger than 9"); Scanner type = new Scanner(System.in); String number1 = type.nextLine();
for( int i = 0; i < number1.length(); i++ ){ int calculate = number1.charAt(i); } } } mh_sh_highlight_all('java');
We were given the assignment to program a lotto game. in our game we should do follow the following steps below, and we are supposed to use atleast tree methods. the first one to receive the array of integers and an integer and check if the int was not entered before. the user should not repeat the same number. the other method will draw all numbers of a game (quantity of numbers to draw is based on the number parameter) and returns them in an array. the last method will display the result of the game. It receives a list of all lines played and a list of all numbers draw.
these are the steps to follow:
1. Ask the user how many lines (games) the user would like to play. Each line is made of five numbers between 1 and 45 (inclusive).
2. Ask the user to enter five numbers between 1 and 45 (inclusive) for each line. The user must NOT be allowed to enter a number more than once for each line.
3. When all the numbers for all the lines are entered, the program should display all lines and asks the user to confirm the game. If the user does NOT confirm the game, the program should start all over again.
4. Draw (generate) five numbers between 1 and 45 (inclusive). The numbers should be unique within the draw.
5. Draw (generate) one number (the bonus number) between 1 and 45 (inclusive). The number should be unique within the draw.
6. Display all the lines played and the result of each line.
7. Ask the user if the person would like to play again, if so the program should start the process all over again.
import javax.servlet.*; import javax.servlet.http.*; import java.sql.*; import java.io.*; public class Test extends HttpServlet {
[Code] ....
This is the basic code structure and I'm trying to figure out this special case with handling the multiple parameters:
I don't want to use String []a=request.getParameterValues("studentname"); as hard code. The reason being the number of rows will be diyamic and I would like to get the column name and then then use an array of string to take values. But how can I connect these to form a query so that the rows goes on inserted one after other.
I have programmed a Router class which has two methods, receive and send.In receive method it receives the plain text from the server through port 2000.Its now all cool.In send method it sends the message to a client through the port 2001 but at the client i get an exception
connection refused:connect import java.io.*; import java.util.*; import java.net.*; import java.sql.*; class Router { String str; public void receive()
