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Java Error: Exception in thread "Thread-5423" java.lang.ArrayIndexOutOfBoundsException [duplicate]

I'm creating two program files (one client one server).
Each file has one thread (one thread for server, one thread for client)
At runtime, there is supposed to be only one server, and there is supposed to be multiple and/or potentially infinite number of clients connecting to the server at the same time)
In order to get multiple clients to run, the user opens multiple command prompt / mac terminal windows (each window being one client) (one window being the server, so it requires at least two windows to run)
Once a client is connected, it can send messages (utf-8 strings) to the server. It will also receive from the server all messages sent from the other connected clients (it will not receive messages sent from itself).
Screenshot of exception in thread / array index out of bounds error (eclipse):
Screenshot of Socket Exception error (server):
Screenshot of error on client side:
Code of Server (ChatServer.java):
import java.io.*;
import java.net.*;
import java.util.*;
import static java.nio.charset.StandardCharsets.*;
public class ChatServer
{
ChatServer chatserver = new ChatServer();
private static Socket socket;
public static void main(String args[])
{
Thread ChatServer1 = new Thread ()
{
public void run ()
{
System.out.println("Server thread is now running");
try
{
int port_number1 = 0;
int numberOfClients = 0;
boolean KeepRunning = true;
if(args.length>0)
{
port_number1 = Integer.valueOf(args[0]);
}
System.out.println("Waiting for connections on port " + port_number1);
try
{
ServerSocket serverSocket = new ServerSocket(port_number1);
socket = serverSocket.accept();
}
catch (IOException e)
{
e.printStackTrace();
}
System.out.println( "Listening for connections on port: " + ( port_number1 ) );
while(KeepRunning)
{
//create a list of clients
ArrayList<String> ListOfClients = new ArrayList<String>();
//connect to client
// socket = serverSocket.accept();
//add new client to the list, is this the right way to add a new client? or should it be in a for loop or something?
ListOfClients.add("new client");
numberOfClients += 1;
System.out.println("A client has connected. Waiting for message...");
ListOfClients.add("new client" + numberOfClients);
//reading encoded utf-8 message from client, decoding from utf-8 format
String MessageFromClientEncodedUTF8 = "";
BufferedReader BufReader1 = new BufferedReader(new InputStreamReader(socket.getInputStream(), "UTF-8"));
String MessageFromClientDecodedFromUTF8 = BufReader1.readLine();
byte[] bytes = MessageFromClientEncodedUTF8.getBytes("UTF-8");
String MessageFromClientDecodedUTF8 = new String(bytes, "UTF-8");
//relaying message to every other client besides the one it was from
for (int i = 0; i < ListOfClients.size(); i++)
{
if(ListOfClients.get(i)!="new client")
{
String newmessage = null;
String returnMessage = newmessage;
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write(returnMessage + "\n");
System.out.println("Message sent to client: "+returnMessage);
bw.flush();
}
}
}
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
try
{
if (socket != null)
{
socket.close ();
}
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
};
ChatServer1.start();
}
}
Code of ChatClient.java:
import java.io.*;
import java.net.*;
import java.util.*;
import static java.nio.charset.StandardCharsets.*;
public class ChatClient
{
static int numberOfClients = 0;
public static void main(String args[])
{
ChatClient chatclient = new ChatClient();
//If I wanted to create multiple clients, would this code go here? OR should the new thread creation be outside the while(true) loop?
while (true)
{
String host = "localhost";
int numberOfClients = 0;
Thread ChatClient1 = new Thread ()
{
public void run()
{
try
{
//Client begins, gets port number, listens, connects, prints out messages from other clients
int port = 0;
int port_1number1 = 0;
int numberofmessages = 0;
String[] messagessentbyotherclients = null;
System.out.println("Try block begins..");
System.out.println("Chat client is running");
String port_number1= args[0];
System.out.println("Port number is: " + port_number1);
if(args.length>0)
{
port = Integer.valueOf(port_number1);
}
System.out.println("Listening for connections..");
System.out.println( "Listening on port: " + port_number1 );
boolean KeepRunning = true;
while(KeepRunning)
{
for(int i = 0; i < numberOfClients; i++)
{
System.out.println(messagessentbyotherclients);
}
try
{
Socket clientSocket = new Socket("localhost", port);
InetAddress inetlocalhost = InetAddress.getByName("localhost");
SocketAddress localhost = new InetSocketAddress(inetlocalhost, port);
clientSocket.connect(localhost, port);
System.out.println("Client has connected");
//client creates new message from standard input
OutputStream os = clientSocket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
}
catch (IOException e)
{
e.printStackTrace();
}
//creating message to send from standard input
String newmessage = "";
try
{
// input the message from standard input encoded in UTF-8 string format
BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
String line = "";
System.out.println( "Standard input (press enter then control D when finished): " );
while( (line= input.readLine()) != null )
{
newmessage += line + " ";
input=null;
}
}
catch ( Exception e )
{
System.out.println( e.getMessage() );
}
//Sending the message to server
String sendMessage = newmessage;
try
{
Socket clientSocket = new Socket("localhost", port);
SocketAddress localhost = null;
clientSocket.connect(localhost, port);
OutputStream os = clientSocket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write(sendMessage + "\n");
bw.flush();
}
catch (IOException e)
{
e.printStackTrace();
}
System.out.println("Message sent to server: "+sendMessage);
}
}
finally
{
}
}
};
ChatClient1.start();
}
}
}
My question is: How should I go about resolving all three errors (it seems like if I change one part of the code, then the other errors will either still exist or be resolved due to that but I could be wrong)? I would also like to know if there's a way to list the number of clients in an arraylist in the server code so that when a client closes their window I can keep the server up by just removing them from the list.

Can't send multiple messages via socket

I'm trying to make a little chat system. I have a console and a client. Right now only the client need to send messages to the console. I can connect successfully to the server, and i can send one message from client to console. The trouble begins after sending the first message. When the first message i can't send any other messages.
I don't know if it's the console that won't read the message or the client that won't send the message. In this case how could i troubleshoot this?
public class ClientMainClass {
private static Socket socket;
public static void main(String args[]) {
try {
String host = "localhost";
int port = 25000;
InetAddress address = InetAddress.getByName(host);
socket = new Socket(address, port);
Scanner scanner = new Scanner(System.in);
System.out.println("Skriv dit username:");
String name = scanner.nextLine();
System.out.println("Du er logget ind som: " + name);
String input;
do{
input = scanner.nextLine();
if (input.equalsIgnoreCase("exit")) {
System.out.println("Du forlod serveren");
socket.close();
continue;
}else {
/*OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);*/
PrintWriter printWriter = new PrintWriter(socket.getOutputStream(),true);
Date date = new Date();
String time = date.getDate()+"/"+date.getMonth()+":"+date.getHours()+":"+date.getMinutes();
//Send the message to the server
String message = time+ " - " + name + ": "+input;
printWriter.println(message);
System.out.println(message);
continue;
}
}while (!(input.equals("exit")));
} catch (Exception exception) {
exception.printStackTrace();
} finally {
//Closing the socket
try {
socket.close();
} catch(Exception e) {
e.printStackTrace();
}
}
}
}
My server:
public class Main{
private static Socket socket;
public static void main(String[] args) {
try {
int port = 25000;
ServerSocket serverSocket = new ServerSocket(port);
System.out.println("Server Started and listening to the port 25000");
while(true) {
//Reading the message from the client
socket = serverSocket.accept();
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
System.out.println(br.readLine());
}
}
catch (Exception e) {
e.printStackTrace();
} finally {
try {
socket.close();
} catch(Exception e){}
}
}
}
To be clear. I can connect to the server. I can send one message from client to console, but no more than one message.

You never read a second line. Your Server accepts a connection, reads one line from that connection and then waits for a new connection, discarding everything that might arrive at the first connection.
Your client however sends all input using the first (and only) connection, which is absolutely correct.
This specific problem can be solved like this:
while(true) {
//Reading the message from the client
socket = serverSocket.accept();
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
while(true){
System.out.println(br.readLine());
}
}
This will cause your program to print everything arriving on that first connection, but it will never accept a second connection.
In order to handle multiple clients, you need a Thread to deal with each one.

can i use multiple times (input/output)stream for different types of data transfer between two nodes [duplicate]

This question already has answers here:
Java multiple file transfer over socket
(3 answers)
Closed 6 years ago.
In this code I use multiple times of retrieve input-output data from two nodes. ... when I use more than two times input output stream it generated this type of error while running this code I need different input and output and that I want to store but unfortunate if I used more than three-time input/output stream it show error
public class Server {
private static Socket socket;
public void connect() throws IOException{
int port = 25000;
ServerSocket serverSocket = new ServerSocket(port);
System.out.println("Server Started and listening to the port 25000");
socket = serverSocket.accept();
}
//Server is running always. This is done using this while(true) loop
//Reading the message from the client
public void first() throws IOException{
connect();
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String number = br.readLine();
System.out.println("Message received from client is "+number);
//Multiplying the number by 2 and forming the return message
String returnMessage;
try
{
int numberInIntFormat = Integer.parseInt(number);
int returnValue = numberInIntFormat*2;
returnMessage = String.valueOf(returnValue) + "\n";
}
catch(NumberFormatException e)
{
//Input was not a number. Sending proper message back to
client.
returnMessage = "Please send a proper number\n";
}
second();
String e=br.readLine();System.out.println(e);
}
public void second() throws IOException{
//Sending the response back to the client.
String returnMessage="Second";
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write(returnMessage);
System.out.println("Message sent to the client is "+returnMessage);
bw.flush();
}
public static void main(String args[]) throws IOException{
Server obj = new Server();
obj.first();
// obj.second();
}public class Server {
private static Socket socket;
public void connect() throws IOException{
int port = 25000;
ServerSocket serverSocket = new ServerSocket(port);
System.out.println("Server Started and listening to the port 25000");
socket = serverSocket.accept();
}
//Server is running always. This is done using this while(true) loop
//Reading the message from the client
public void first() throws IOException{
connect();
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String number = br.readLine();
System.out.println("Message received from client is "+number);
//Multiplying the number by 2 and forming the return message
String returnMessage;
try
{
int numberInIntFormat = Integer.parseInt(number);
int returnValue = numberInIntFormat*2;
returnMessage = String.valueOf(returnValue) + "\n";
}
catch(NumberFormatException e)
{
//Input was not a number. Sending proper message back to client.
returnMessage = "Please send a proper number\n";
}
second();
String e=br.readLine();System.out.println(e);
}
public void second() throws IOException{
//Sending the response back to the client.
String returnMessage="Second";
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write(returnMessage);
System.out.println("Message sent to the client is "+returnMessage);
bw.flush();
}
public static void main(String args[]) throws IOException{
Server obj = new Server();
obj.first();
// obj.second();
}
public class client {
private static Socket socket;
//public void connect() throws UnknownHostException, IOException{
//}
public void first() throws IOException{
String host = "localhost";
int port = 25000;
InetAddress address = InetAddress.getByName(host);
socket = new Socket(address, port);
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
String number = "2";
String sendMessage = number + "\n";
bw.write(sendMessage);
bw.flush();
System.out.println("Message sent to the server : "+sendMessage);
String sendMessage1="3333";
bw.write(sendMessage1);
bw.flush();
//second();
}
public void second1() throws IOException{
//Get the return message from the server
InputStream is = socket.getInputStream();
InputStreamReader isr;
isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String message = br.readLine();
System.out.println("Message received from the server : " +message);
socket.close();
}
public static void main (String argd[]) throws IOException{
client obj1 = new client();
obj1.first();
}
-----------------------------------------
error
Message received from client is 2
Message sent to the client is Second
Exception in thread "main" java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:209)
at java.net.SocketInputStream.read(SocketInputStream.java:141)
at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)

InputStream and OutputStream are intended to work with a single source and destination. Once you obtain an InputStream that reads from file/socket/whatever source you can use it for multiple consecutive reads. But once you are done reading from that source you need to invoke close() method on your stream.
Not closing your stream is classic reason for a memory leak in Java. In fact for that reason you ALWAYS expected to surround the usage of your source with try catch and always invoke close() method in finally statement. So to insure that it is always invoked. Further more, since close() method itself can cause an Exception, within final statement you need to surround it with its own try-catch. Starting from java 7 there is a new feature called "try with resources" that deals with this particular issue.
Please read about it here

android.os.NetworkOnMainThreadException (client application android / serveur application java) (send string)(using emulator localhost) [duplicate]

This question already has answers here:
How can I fix 'android.os.NetworkOnMainThreadException'?
(66 answers)
Closed 7 years ago.
the class of client in android application (using emulator localhost), sending a string to my java application (serveur) :
public class Client_socket extends MainActivity{
private static Socket socket;
public static void lance()
{
try
{
String host = "localhost";
int port = 25000;
InetAddress address = InetAddress.getByName(host);
socket = new Socket("127.0.0.3", port);
//Send the message to the server
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
String nom = "premiere";
String sendMessage = ism + "\n";
bw.write(sendMessage);
bw.flush();
System.out.println("Message sent to the server : "+sendMessage);
//Get the return message from the server
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String message = br.readLine();
System.out.println("Message received from the server : " +message);
}
catch (Exception exception)
{
exception.printStackTrace();
}
finally
{
//Closing the socket
try
{
socket.close();
}
catch(Exception e)
{
e.printStackTrace();
}
}
}
}
the class of serveur in java application how recive my string :
what the ip and port can i use?, and how can i get my ip?
public class Server
{
private static Socket socket;
public static void main(String[] args)
{
try
{
int port = 25000;
ServerSocket serverSocket = new ServerSocket(port);
System.out.println("Server Started and listening to the port 25000");
//Server is running always. This is done using this while(true) loop
while(true)
{
//Reading the message from the client
socket = serverSocket.accept();
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String nom = br.readLine();
System.out.println("Message received from client is "+nom);
}
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
try
{
socket.close();
}
catch(Exception e){}
}
}
}

Make sure you execute network operations in a background thread:
new Thread(new Runnable() {
#Override
public void run() {
lance(); // call your network method here
}
}).start();

java Socket programming Server Client

I'm trying to program a Server Client program where the CLIENT will be prompt if the SERVER closes or loses connection. What happens is once I connect the server and the client then disconnects the server it doesn't go to the ConnectException part
example: I opened the Server and Client connects, in the Client it will show that "You are connected to the Server", then if the Server disconnects there should be a "Server is disconnected". and when the Server reopens it will prompt the Client that he's connected to the Server
How can I continuously check if the Server is open or disconnected
here's my code:
SERVER
public class Server
{
private static Socket socket;
public static void main(String[] args)
{
try
{
int port = 25000;
ServerSocket serverSocket = new ServerSocket(port);
//Server is running always. This is done using this while(true) loop
while(true)
{
//Reading the message from the client
socket = serverSocket.accept();
System.out.println("Client has connected!");
InputStream is = socket.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String number = br.readLine();
System.out.println("Message received from client is "+number);
//Multiplying the number by 2 and forming the return message
String returnMessage;
try
{
int numberInIntFormat = Integer.parseInt(number);
int returnValue = numberInIntFormat*2;
returnMessage = String.valueOf(returnValue) + "\n";
}
catch(NumberFormatException e)
{
//Input was not a number. Sending proper message back to client.
returnMessage = "Please send a proper number\n";
}
//Sending the response back to the client.
OutputStream os = socket.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os);
BufferedWriter bw = new BufferedWriter(osw);
bw.write(returnMessage);
System.out.println("Message sent to the client is "+returnMessage);
bw.flush();
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
CLIENT
public class Client
{
private static Socket socket;
public static void main(String args[])
{
Scanner input=new Scanner(System.in);
try
{
String host = "localhost";
int port = 25000;
InetAddress address = InetAddress.getByName(host);
socket = new Socket(address, port);
System.out.println("Connected to the Server");
}
catch (ConnectException exception)
{
System.out.println("Server is still offline");
}
catch(IOException ex)
{
System.out.println("Server got disconnected");
}
}
}

Well, the best way to tell if your connection is interrupted is to try to read/write from the socket. If the operation fails, then you have lost your connection sometime.
So, all you need to do is to try reading at some interval, and if the read fails try reconnecting.
The important events for you will be when a read fails - you lost connection, and when a new socket is connected - you regained connection.
That way you can keep track of up time and down time.
you can do like this
try
{
Socket s = new Socket("address",port);
DataOutputStream os = new DataOutputStream(s.getOutputStream());
DataInputStream is = new DataInputStream(s.getInputStream());
while (true)
{
os.writeBytes("GET /index.html HTTP/1.0\n\n");
is.available();
Thread.sleep(1000);
}
}
catch (IOException e)
{
System.out.println("connection probably lost");
e.printStackTrace();
}
or you can simply et connection time out like this socket.setSoTimeout(timeout); to check connectivity
or you can use
socket.getInputStream().read()
makes the thread wait for input as long as the server is connected and therefore makes your program not do anything - except if you get some input and
returns -1 if the client disconnected
or what you can do is structure your code in this way
while(isConnected())
{
// do stuffs here
}