Communicating With Remote Computers Using Socket
Dec 7, 2014
I have an android device which i want to be able to switch off remotely from a console hosted on the amazon cloud.The console is a simple html button that on click sends a command to a listening server on an android device that i know its ip address.
My question,is this even possible given the huge security bleach this would present to rogue apps to be able to order actions on remote devices not started by the device owner?.
The way i know the ip is via once internet is connected on an android deice,i shall then make it announce its ip that it has been assigned by the service provider,then starting a server to accept external connections.
My theory could be wrong if what i want is not permitted.
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May 26, 2014
I am working on a project with client/server relationship and I want the client to be able to transfer their personal music files over the socket. Every time I attempt to do it the file is created but it is empty.
Server code:
Java Code:
public class Server extends JFrame {
//===============================
// FIELDS
//===============================
// connection essentials
private ServerSocket server;
private Socket connection;
[Code] ....
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Apr 3, 2014
I'm working on an assignment right now which involves passing a variable series of numbers to the Server to be sorted into the correct order and returned to the client.
So far I have it connecting to the server and asking for my numbers, and I am entering each number and pressing return, and it is accepting each number individually.
One (smaller I think) problem i'm having is with the client code, specifically the while loop.. I've tried to code it so that when I enter a full stop ('.') the program will stop asking me for more numbers and move on to sending them to the server.. but instead it just crashes giving an error.. heres an example
"Enter a number: 1
Enter a number: 3
Enter a number: 2
Enter a number: 1.
java.lang.NumberFormatException: For input string: "1."
at java.lang.NumberFormatException.forInputString(Num berFormatException.java:65)
[Code] ....
Here's the client code in full
package numberSortprogram;
import java.io.*;
import java.net.ServerSocket;
public class NumSortClient {
public static void main(String[] args) {
InputStreamReader is = new InputStreamReader(System.in);
[Code] ....
The big problem that I have is figuring out how to send the sorted array back to the client..
So, what im trying to get to happen is-
-Client is asked to enter numbers
-Client enters series of numbers into an array
-Array is converted to a string and sent to the server
-String is then split into an array of strings and sorted using compareTo (don't know if this is the best way?)
-Sorted array is sent back to client and displayed.
fyi this is making use of streamsockets..
All of the rest of my code is below:
package numberSortprogram;
import java.io.IOException;
import java.net.*;
import java.util.regex.PatternSyntaxException;
public class NumSortServer {
public static void main(String[] args) {
int serverPort = 4444; // default port
if (args.length == 1 )
[Code] .....
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Feb 3, 2014
Me and my brother decided to make a relatively simple client/server program where clients get into a simple chat lobby and can invite others to play small games(like pong). The basic server code has been written, and we have made a special client that is used for debugging.
We use a self-defined protocol of Strings where a message looks like "4-|user,pass". The number before the delimiter "-|" is the operation code, that tells the server what kind of message this client sends. Based on that number, the server dispatches the message to the appropriate handler method. 4 is authentication for example, and the handler looks the user and pass up in a file and if found, returns true, otherwise, false. Then the server responds to the clinet with 2-|"any message" where the client will recognize opcode 2 as a "authentication accepted" and proceed with the next part of client code. In a similar way, we plan to write all message types(both in the game, in the lobby and in a game setup room).
While testing we ran into a problem where the BufferedReader .readLine() does not seem to be a blocking call like it should be, so the client keeps spamming 'null' in the output field that we made to see the server response to the message we send. When we try to debug the server code and set breakpoints at the suspicious locations, it strangely skips both while(true) loops without activating either breakpoint and executes the finally{} code, even though the client did not close the connection and the second while loop was never entered. The first while loop IS entered though, because the test client gets a "0" on its output, which is the server message indicating "please authenticate yourself".
We decided to use messages in a string format and decode it at both sides as it seemed easier than transmitting java objects and making sure they are of the same type, also for reducing overhead as much of possible.URL....
package Chatroom;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.HashSet;
[code]....
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Dec 27, 2014
I want to write a java program which would do remote file transfer without using Byte array..how I can get sample code program??
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Sep 22, 2014
I have a servlet. Users from other machines access that servlet and I want to capture the remote user's UserName and do validation over that.It's just a simple servlet and no login/password is present. I tried request.getRemoteUser(), but its of no luck.
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May 21, 2014
I am developing a web application in java(JSF 2.0 - Prime Faces). I need to do below operation. My appllication is running on WLS server. WLS is deployed on a server(say Machine-X). In my application i have a requirement , where i have to copy file from Machine-X to another Machine-Y. The Machine-Y is access restricted.
When i tried to copy the file from my app, getting no access exception. I have full control over Machine-Y. We cannot use SFTP as SFTP cannot be installed on target machine(Machine-Y). Robocopy is failing for some use cases. Is there any other way we can copy/write file from one server to other by providing userid/password in java
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Mar 11, 2014
i'm having issues with pass by reference between remote EJB method calls. Below is what i'm trying to do. The EJB method calls are made using remote (EJBObject) interface.
insertEmployeeRecord(Employee employee) {
employeeEJB.insertEmployee(employee);
empDetailsEJB.insertEmpDetails(employee);
}
insertEmployee(Employee employee)
[Code] ....
All the EJBs have below configuration in the weblogic-ejb-jar.xml file.
<enable-call-by-reference>true</enable-call-by-reference>
I'm using Weblogic server 10.3.0.4 and JDK160_21.
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Jan 15, 2015
I'm working on an application I made a few years ago. At that time I connected to a local database so my address was 'jdbc:mysql://localhost:3306/'. That database is long gone so I recreated it on one of my hosted servers but I'm a little unsure of how to connect to it. At the moment I'm trying "jdbc:mysql://www.mydomain.com:3306/" but it is giving me an access denied error.
java.sql.SQLException: Access denied for user 'myusername'@'c-[my-ip].hsd1.pa.comcast.net' (using password: YES)Every result on Google seems to use localhost so I'm having a little difficulty figuring out the correct format.
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Aug 5, 2014
jboss 7.1.1
EJB 2.1
Though it may seem strange but in one of the application i work on still uses EJB 2.1 entity beans.While looking at the deployment log, seems like each Entity bean is registered using both remote-home and remote interfaces.
java:app/EJBApp/Entity!com.abc.remote.Remote
java:app/EJBApp/Entity!com.abc.remote.RemoteHome
Using the remote-home's JNDI lookup i was able to get the EJBObject proxy and subsequently create and use the entity.But what about the remote interface JNDI lookup ? Reason i am asking is that one needs to create an entity before use it. That said, how to use the object that i get from remote interface JNDI lookup ? Note that the class of the returned object says its "com.sun.proxy.$Proxy13" type.The JNDI location i am using "java:app/EJBApp/Entity!com.abc.remote.Remote"
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Dec 14, 2014
a direct solution for connecting a remote Unix server through telnet connection from java application.
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Dec 16, 2013
How to store the images captured from a system using web cam(from where the web application accessed) to a folder of system(where the web application is deployed) connected through lan......?
I have used applets to connect to web cam.
import java.applet.Applet;
import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Frame;
import java.awt.Graphics;
[Code] ....
Through this applet I am capturing the image and saving in the application deployed directory and accessing this image through a servlet. Every thing works fine in my system but when i try to capture from other systems connected through lan the image not saving in my system.
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Jun 10, 2014
I would like to ask how i can create a bidirectional folder copy system with SFTP JSch is there any example. Like i see the code can only transfer file, I need to transfer a folder with many files from my pc to a server and the opposite.
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May 21, 2014
I am trying to make connection with oracle database but when i run java file it's raise an error
"classnotfoundexception oracle.jdbc.driver.oracledriver"
DriverManager.getConnection(
"jdbc:oracle:thin:@erp:1521:ORCL", "apps",
"apps");
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Mar 3, 2015
From java running on Windows, I need to access a file on a remote Ubuntu machine. I use the following:
URL U = new URL ( "http://" + SERVER_IP + ":" + SERVER_PORT + "/" + ClsName + ".class" );
where:
SERVER_IP is the Ubuntu IP address obtained from any site that shows the IP address of the machine you are using.SERVER_PORT is the Ubuntu port where the server is listening.
Now:
Do I need to modify this code any further?Do I need to configure the Windows and/or Ubuntu machine(s) for this to work?
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Aug 14, 2014
I have a Linux Server Debian 7 x86_64 Minimal With java version "1.7.0_65" installed..Its an online Game Server wich Players can join just like other Services.Every 10 - 15 minutes all the players get kicked from the server and get this messege: "internal exception: java.io.ioexception: an existing connection was forcibly closed by remote host"
The players can't join the server for 10 seconds and the server console doesn't show anything for 10 seconds.it doesnt show that the players even left! and when the players try to join they get htis messege: "same nick is already playing"
After 10 seconds everything will work and players can join again and server console say that everyone left and joined..But that happens again after 10 minutes and im losing lots of players because of this error.
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Apr 10, 2014
I am trying to check SFTP connection to remote server using enchanter jar. Mine is not a multi-threaded application. PFB sample code...
.....
SSH ssh = new DefaultSS();
ssh.setTimeOut(10000);
ssh.connect("myserver","myusername","mypassword");
ssh.sendLine("cd /u");
ssh.sendLine("sftp -B batch.file utodldse@claoesdsdd.com");
ssh.getLine();
.....
note - the batch.file contains only 1 statement. Please find below.
---
bye
---
But the above program is getting is stuck at times when the server is not responding. It goes into infinite hung state.
Is there some alternative ways to set timeout ?
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Apr 1, 2012
I have a doubt about how to design a web application which has their persistent objects in a service layer in a remote server, i mean a business application. So, once we have a web application as a client of this remote business application, how those persistent objects should be mapped in web front?
Should I either pack all jpa annotated classes into the web front application or there is another neat way to do this?
I was intending in copy all persistent classes present in the remote business application into the web app package, i know it's not the best way to get what i need.
What is a more appropriate design for a web application which must get some objects from a remote business application and persist some other objects there?
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Jan 30, 2014
I am trying to connect a remote machine but I can't. There is a shared folder in the remote machine, when I write the path to file browser in local machine, it does not find the path specified. Both machines have successful network condition and ping each other. Also, the shared folder is opened to everyone, there should not be a permission problem, right?
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Oct 23, 2013
I have an stand alone client to use a remote ejb with some methods. All works fine, but when I pass an entity class as parameter from the stand alone client to the remote ejb, the entity class is received as null.
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Feb 13, 2014
I'm developing a web-based chatting system using JSP and socket.
The problem i am facing is that the sender can send message but on the receiver side we have to manually refresh the page. The sender stays into blocking mode until the receiver refresh its page !
after that i've implemented auto-refresh on the receiver side and "Connection Refused" exception is generated.
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Mar 4, 2014
Currently I have socket of the tcp version.
Java Code:
final ServerSocket serverSocketConn = new ServerSocket(9000);
while (true) {
try {
Socket socketConn1 = serverSocketConn.accept();
new Thread(new ConnectionHandler(socketConn1)).start();
[Code] .....
I managed to convert this final DatagramSocket serverSocketConn = new DatagramSocket (9000);
Now I am stuck here
Socket socketConn1 = serverSocketConn.accept();
new Thread(new ConnectionHandler(socketConn1)).start();
Can I use this or I need to create a manual thread pooling for UDP ?
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May 22, 2014
I can have up to 100,000 simultaneous connections to a udp socket, which needs to be handled by separate threads. Each of the connections talk to a c program on an embedded device that sends and responds with an array of unsigned chars. Now Java does not have an unsigned char type. The closest you can use is a short. But DatagramPacket requires a byte argument:
public class Socket {
public Socket(int port) throws IOException {
new SocketThread().start();
} }
public class SocketThread extends Thread {
protected DatagramSocket socket = null;
[Code] .....
So how can I go about reading and writing unsigned chars over a udp socket?
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Apr 4, 2015
if i send messages as in the code below, is there a way to read only one message, if the client doesn't know how long it is (or if he only knows the maximum length)?in the documentation it says, that the method read(byte[]) reads until no data ist available or end of file is decteted. What does the latter mean? Can i extend the array that i sent by a byte that signals the end? Here is my Code:
Server
public class Server implements Runnable{
ServerSocket server;
HashMap<Short,Socket> clients;
public Server(){
clients = new HashMap<>();
[code]....
Both are startet in seperate threads. At the moment the first output of the client is "12 bytes read", and then continously "-1 bytes read"(because the server closes).
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Feb 10, 2014
I have been working with socket programming. I was trying to develop a two way communication from server to client. The data is being received when sent from server to client but there is a problem when I am sending from client to server.
I am getting an error as "Socket is closed" pointing to the line where I have created a BufferedReader. I have simplified some part of my code to be very specific.
Code attached.
import java.io.*;
import java.net.*;
import java.util.*;
public class Server
{
public static void main(String args[])
{
String id="policeone";
int hashcodeid=0;
[Code] ....
Error::
Receiving string from client: 'java.net.SocketException: Socket is closed
at java.net.Socket.getInputStream(Socket.java:872)
at Server.main(Server.java:51)
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Sep 21, 2014
I want to download objects (css , jpeg, html ,png ) using sockets in java without using httpurlconnection . How can i do this with simple socket library ?
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