We Keep Coding

Server doesn't forward message to all in the chat

i am trying to create a simple chat app using java sockets, the server is threaded, when a client connects its socket is added to an ArrayList, so that i can send to all in that list.
the problem is when 3 clients are connected, the for loop that sends doesn't work properly, for ex : client 0 sends to both 1 and 2 but client 2 doesn't send to anyone :(
The server and the ClientHandler :
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.Scanner;
public class MainServer {
private static int portnumber = 6968;
static ArrayList <ClientHandler> allClients = new ArrayList<>();
public static void main(String[] args) throws Exception {
// init
// server works by default on localhost
ServerSocket serversocket = new ServerSocket(portnumber);
int clientNo = 0;
System.out.println("server is running on port : " + portnumber);
while (true) {
// creating a socket for each connection
Socket clientsocket = null;
try {
// receiving incoming requests from users/clients
clientsocket = serversocket.accept();
// input and output from client
PrintWriter out = new PrintWriter(clientsocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(clientsocket.getInputStream()));
// create a threads
ClientHandler ch = new ClientHandler(clientsocket, "Client#" + clientNo, in, out);
// adding to the clientList
allClients.add(ch);
System.out.println(ch.clientName + " has joined");
Thread clientThread = new Thread(ch);
clientThread.start();
// decrease when user leaves
clientNo++;
} catch (Exception e) {
clientsocket.close();
e.printStackTrace();
System.exit(1);
//out.close();
//in.close();
//clientSocket.close();
//serverSocket.close();
}
}
}
}
// handle client requests
public class ClientHandler implements Runnable{
public String clientName;
public Socket clientsocket = null;
public boolean active = false;
private BufferedReader inp;
private PrintWriter out;
private final String EXIT_STR = "exit";
public Scanner clientSc = new Scanner(System.in);
public ClientHandler(Socket socket, String name, BufferedReader inp, PrintWriter out) {
this.clientsocket = socket;
this.clientName = name;
this.inp = inp;
this.out = out;
// active when the thread is created
this.active = true;
}
#Override
public void run() {
// getting the output temp
String recivedMsg = "";
while (true) {
try {
recivedMsg = inp.readLine();
System.out.println(recivedMsg);
// check for ctrl+C
if (recivedMsg.equals(this.EXIT_STR)){
// send to all
System.out.println(this.clientName + " exits");
// close the connection and break
this.active = false;
this.clientsocket.close();
// bye
break;
}
// send to all except me
for (ClientHandler client : MainServer.allClients){
if (!client.clientName.equals(this.clientName)){
client.out.println(this.clientName + ":" + recivedMsg);
client.out.flush();
break;
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
try {
// clean
this.clientsocket.close();
this.inp.close();
this.out.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
The client :
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.Scanner;
public class Client {
private String hostName;
private int portNumber;
// set connction and server
public PrintWriter out = null;
public BufferedReader in = null;
public Socket clientSocket = null;
Client(String hostName, int port) {
this.hostName = hostName;
this.portNumber = port;
// setting the connction
this.setConnection();
}
private void setConnection () {
try {
this.clientSocket = new Socket(this.hostName, this.portNumber);
this.out = new PrintWriter(this.clientSocket.getOutputStream(), true);
this.in = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
} catch (Exception e) {
e.printStackTrace();
System.exit(1);
}
}
public void sendMessageToServer(String msg) {
//System.out.println("The msg is : " + msg);
out.println(msg);
}
public String readMessage() {
String outputMsg = "";
try {
outputMsg = in.readLine();
} catch (IOException e) {
e.printStackTrace();
}
return outputMsg;
}
// shit cleaning
public void closeSession(){
try {
this.out.close();
this.in.close();
this.clientSocket.close();
} catch (IOException e) {
e.printStackTrace();
System.exit(1);
}
System.out.println("Session has been terminated!");
}
public static void main(String args[]) throws IOException{
// init
String host = "localhost";
int port = 6968;
Client newClient = new Client(host, port);
// // send a message
Scanner sc = new Scanner(System.in);
Thread sendMsg = new Thread(new Runnable() {
#Override
public void run() {
while (true) {
try {
String userInput = sc.nextLine();
newClient.sendMessageToServer(userInput);
if (userInput.equals("exit")) {
System.exit(1);
}
} catch (Exception e) {
System.exit(1);
}
}
}
});
Thread getMsg = new Thread(new Runnable() {
#Override
public void run() {
while (true) {
String msgRead = "";
try {
msgRead = newClient.readMessage();
System.out.println(msgRead);
} catch (Exception e) {
System.exit(1);
}
}
}
});
sendMsg.start();
getMsg.start();
}
}
I think the problem is here :
// send to all except me
for (ClientHandler client : MainServer.allClients){
if (!client.clientName.equals(this.clientName)){
client.out.println(this.clientName + ":" + recivedMsg);
client.out.flush();
break;
}
}

The fix is straightforward: remove the break statement from the loop where you think the problem is.
This break statement causes the loop through all the ClientHandlers to stop as soon as it sends the message to one client. You don't want this: you want this loop to keep going and send the message to all clients other than the one that wrote the message.

BufferedReader readLine() stuck

I'm writing a TCP multi Client/Server app that works in an infinite loop.
What happens:
Client types "COMMANDS" and expects to get available commands from server.
Server sends lines to client.
Client reads server input line-by-line and is stuck after the last one is written.
Expected result:
Client is prompted for keyboard input.
Input is written to server.
Server sends back text.
Client reads server input line-by-line.
End of loop.
user types commands > server responds > user gets to type commands again
I know that BufferedReader would stop reading lines once I close the socket. However, that's not what we want since it has to work infinitely.
How do I exit the loop?
Client method:
public class Client {
private final Socket clientSocket;
private final BufferedReader clientInput;
private final PrintWriter clientOutput;
private final BufferedReader keyboardInput;
public Client() throws IOException {
this.clientSocket = new Socket(InetAddress.getLocalHost(), 13370);
this.clientInput = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
this.clientOutput = new PrintWriter(clientSocket.getOutputStream(), true);
this.keyboardInput = new BufferedReader(new InputStreamReader(System.in));
}
public static void main(String[] args) throws IOException {
Client client = new Client();
client.init();
}
private void init() {
try {
while (true) {
System.out.print("> ");
String args = keyboardInput.readLine().trim().replaceAll("\\s+", " ");
clientOutput.println(args.toUpperCase());
// the loops doesn't seem to stop after reading all input lines
String line;
while ((line = clientInput.readLine()) != null) {
System.out.println(line);
}
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class ClientHandler implements Runnable {
private final int id;
private final Socket clientSocket;
private final PrintWriter serverOutput;
private final BufferedReader serverInput;
// private final ClientFiles clientFiles;
public int getId() {
return id;
}
public ClientHandler(int id, Socket clientSocket) throws IOException {
this.id = id;
this.clientSocket = clientSocket;
this.serverInput = new BufferedReader(new InputStreamReader(this.clientSocket.getInputStream()));
this.serverOutput = new PrintWriter(this.clientSocket.getOutputStream(), true);
// this.clientFiles = new ClientFiles(id, clientSocket);
}
#Override
public void run() {
try {
String command;
while ((command = serverInput.readLine()) != null) {
executeCommand(command.split(" "));
}
} catch (IOException e) {
e.printStackTrace();
} finally {
closeConnection();
removeFromHosts();
}
}
private void executeCommand(String[] input) throws IOException {
String command = input[0];
// String option = input[1];
switch (command) {
case "COMMANDS": {
getCommands();
break;
}
// case "LIST_LOCAL": {
// listFiles();
// break;
// }
// case "LIST_FILES": {
// listFiles(option);
// }
// case "PULL": {
// pull(clientSocket, option);
// }
// case "PUSH": {
// push(clientSocket, option);
// }
case "DISCONNECT": {
closeConnection();
break;
}
default: {
write("Invalid command.");
getCommands();
break;
}
}
}
private String read() throws IOException {
return serverInput.readLine();
}
private void write(String message) {
serverOutput.println(message);
}
private void getCommands() {
write("AVAILABLE COMMANDS:");
write("\tCOMMANDS");
write("\t\tlists available commands");
write("\tLIST_HOSTS");
write("\t\tlists hosts connected to server");
write("\tLIST_FILES");
write("\t\tlists files from all hosts connected server");
write("\tLIST_LOCAL");
write("\t\tlists local files");
write("\tLIST_FILES [HOSTS]...");
write("\t\tlists files from provided hosts connected server");
write("\tPULL [HOST] [FILE]");
write("\t\tdownloads file from host");
write("\tPUSH [HOST] [FILE]");
write("\t\tuploads file to host");
write("\tDISCONNECT");
write("\t\tdisconnects client from server");
}
private void closeConnection() {
try {
serverInput.close();
serverOutput.close();
clientSocket.close();
removeFromHosts();
} catch (IOException e) {
e.printStackTrace();
}
}
private void removeFromHosts() {
Server.getClients().remove(this);
}
}
Server just accepts new clients and starts new threads.
public class Server {
private static final AtomicInteger count = new AtomicInteger(1);
private static final ArrayList<ClientHandler> clients = new ArrayList<>();
public static void main(String[] args) {
Server.init();
}
public static void init() {
System.out.println("Opening server socket...");
try (
ServerSocket serverSocket = new ServerSocket(13370)
) {
System.out.println("Server socket opened at port: " + serverSocket.getLocalPort());
while (true) {
System.out.println("Waiting for client connection...");
Socket clientSocket = serverSocket.accept();
System.out.println("Client connected.");
ClientHandler client = new ClientHandler(count.getAndIncrement(), clientSocket);
clients.add(client);
System.out.println(clients);
new Thread(client, "client-" + client.getId()).start();
}
} catch (IOException e) {
e.printStackTrace();
}
}
public static ArrayList<ClientHandler> getClients() {
return clients;
}
}

your client is waiting for more lines.
In your code
while ((line = clientInput.readLine()) != null) {
System.out.println(line);
}
clientInput.readLine() will never return null if server does not close the connection. The execution stops waiting more data.
I suggest to implements a solution like insert an empty line or a special char to signal the client that the response to the command is finished.

Java Socketing: My server class constantly takes in input but my client doesn't?

Try to do some concurrent messaging between the server and the client. When they first connect to eachother and the Server sends the test string, the client gets it perfectly fine the first time. And the client can SEND messages just fine to the Server. But my Client class cant constantly check for messages like my Server can and idk what's wrong. Any suggestions?
Server class code:
import java.lang.*;
import java.io.*;
import java.net.*;
import java.util.Random;
import java.util.concurrent.*;
import java.util.logging.Level;
import java.util.logging.Logger;
public class Server {
String testMessage = "You are now connected and can begin chatting!";
boolean connected = false;
int port;
public Server(int port) {
this.port = port;
}
public void Open() {
//creates Threadpool for multiple instances of chatting
final ExecutorService clientProcessingPool = Executors.newFixedThreadPool(10);
Runnable serverTask = new Runnable() {
#Override
public void run() {
try {
System.out.println("Opening...");
ServerSocket srvr = new ServerSocket(port);
while (true) {
Socket skt = srvr.accept();
clientProcessingPool.submit(new ClientTask(skt));
}
} catch (Exception e) {
try {
System.out.println(e);
System.out.print("You're opening too many servers in the same location, fool!\n");
ServerSocket srvr = new ServerSocket(port);
while (true) {
Socket skt = srvr.accept();
clientProcessingPool.submit(new ClientTask(skt));
}
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
};
Thread serverThread = new Thread(serverTask);
serverThread.start();
}
private class ClientTask implements Runnable {
private final Socket skt;
private ClientTask(Socket skt) {
this.skt = skt;
}
#Override
public void run() {
//for sending messages
if (connected == false) {
System.out.println("======================");
System.out.println("Server has connected!");
processMessage(testMessage);
}
//for receiving messages
while (true) {
try {
// Read one line and output it
BufferedReader br = new BufferedReader(new InputStreamReader(skt.getInputStream()));
String incomingMessage = br.readLine();
if (incomingMessage != null) {
System.out.println("Server: Received message: " + incomingMessage);
processMessage(incomingMessage);
}
//br.close();
//skt.close(); //maybe delete
} catch (Exception e) {
System.out.println("Server had error receiving message.");
System.out.println("Error: " + e);
}
}
}
//for processing a message once it is received
public void processMessage(String message) {
PrintWriter out = null;
try {
out = new PrintWriter(skt.getOutputStream(), true);
} catch (IOException ex) {
System.out.println(ex);
System.out.println("Server had error sending message.");
}
System.out.print("Server: Sending message: " + message + "\n");
out.print(message);
out.flush();
connected = true;
try {
skt.shutdownOutput();
//out.close();
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
}
Client class code:
import java.lang.*;
import java.io.*;
import java.net.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JOptionPane;
class Client {
public String message;
Socket skt;
public int port;
public Client(int port) {
this.port = port;
}
//for receiving messages from Server
public void receiveMessage() {
final ExecutorService clientProcessingPool = Executors.newFixedThreadPool(10);
Runnable serverTask = new Runnable() {
#Override
public void run() {
try {
skt = new Socket(InetAddress.getLocalHost().getHostName(), port);
while (true) {
clientProcessingPool.submit(new Client.ClientTask(skt));
}
} catch (IOException ex) {
Logger.getLogger(Client.class.getName()).log(Level.SEVERE, null, ex);
}
}
};
Thread serverThread = new Thread(serverTask);
serverThread.start();
}
//for sending messages to Server
public void sendMessage(String outgoingMessage) throws IOException {
try {
skt = new Socket(InetAddress.getLocalHost().getHostName(), port);
PrintWriter pw = new PrintWriter(skt.getOutputStream());
System.out.println("Client: Sending message: " + outgoingMessage);
pw.print(outgoingMessage);
pw.flush();
skt.shutdownOutput();
//skt.close(); //maybe delete
} catch (Exception e) {
System.out.println(e);
System.out.print("Client had error sending message.\n");
JOptionPane.showMessageDialog(null, "That User is not currently online.", "ERROR!!", JOptionPane.INFORMATION_MESSAGE);
}
}
private class ClientTask implements Runnable {
private final Socket skt;
private ClientTask(Socket skt) {
this.skt = skt;
}
#Override
public void run() {
while (true) {
try {
BufferedReader in = new BufferedReader(new InputStreamReader(skt.getInputStream()));
//while (!in.ready()) {}
String incomingMessage = in.readLine();
if (incomingMessage != null) {
System.out.println("Client: Received message: " + incomingMessage); // Read one line and output it
message = incomingMessage;
}
//skt.shutdownInput();
//in.close();
//skt.close(); //maybe delete
} catch (Exception e) {
System.out.print("Client had error receiving message.\n");
}
}
}
}
}

Streams cannot be re-wrapped. Once assigned to a wrapper, they must use that wrapper for the entire life-cycle of the stream. You also shouldn't close a stream until you are done using it, which in this case isn't until your client and server are done communicating.
In your current code, there are a few times where you re-initialize streams:
while (true) {
try {
//Each loop, this reader will attempt to re-wrap the input stream
BufferedReader br = new BufferedReader(new InputStreamReader(skt.getInputStream()));
String incomingMessage = br.readLine();
if (incomingMessage != null) {
System.out.println("Server: Received message: " + incomingMessage);
processMessage(incomingMessage);
}
//don't close your stream and socket so early!
br.close();
skt.close();
} catch (Exception e) {
//...
}
You get the idea; you can use this knowledge to find the stream problems in your client code as well.
With that said, servers are the middle-man between multiple clients. If you want to be able to type in the server's console to send a message to clients, it shouldn't go to only 1 client (unless you had a system that allowed you to specify a name). You need to store every connection in some kind of collection so when you type in the server's console, it goes to every client that's connected. This also helps when a client wants to send a message to every other client (global message). The server's main thread is primarily for accepting clients; I created another thread to allow you to type in the console.
As for your streams, you should create them whenever you start the ClientTask, both server side and client side:
public class Server {
private ExecutorService executor = Executors.newFixedThreadPool(10);
private Set<User> users = new HashSet<>();
private boolean running;
private int port;
public Server(int port) {
this.port = port;
}
public void start() {
running = true;
Runnable acceptor = () -> {
try(ServerSocket ss = new ServerSocket(port)) {
while(running) {
User client = new User(ss.accept());
users.add(client);
executor.execute(client);
}
} catch(IOException e) {
//if a server is already running on this port;
//if the port is not open;
e.printStackTrace();
}
};
Runnable userInputReader = () -> {
try(Scanner scanner = new Scanner(System.in)) {
while(running) {
String input = scanner.nextLine();
for(User user : users) {
user.send(input);
}
}
} catch(IOException e) {
//problem sending data;
e.printStackTrace();
}
};
Thread acceptorThread = new Thread(acceptor);
Thread userThread = new Thread(userInputReader);
acceptorThread.start();
userThread.start();
}
public void stop() {
running = false;
}
public static void main(String[] args) {
new Server(15180).start();
System.out.println("Server started!");
}
}
In the run() method is where the streams should be wrapped.
class User implements Runnable {
private Socket socket;
private boolean connected;
private DataOutputStream out; //so we can access from the #send(String) method
public User(Socket socket) {
this.socket = socket;
}
public void run() {
connected = true;
try(DataInputStream in = new DataInputStream(socket.getInputStream())) {
out = new DataOutputStream(socket.getOutputStream());
while(connected) {
String data = in.readUTF();
System.out.println("From client: "+data);
//send to all clients
}
} catch(IOException e) {
//if there's a problem initializing streams;
//if socket closes while attempting to read from it;
e.printStackTrace();
}
}
public void send(String message) throws IOException {
if(connected) {
out.writeUTF(message);
out.flush();
}
}
}
It's pretty much the same idea with the client:
1. Connect to Server
2. Create "communication" thread
3. Create "user input" thread (to receive input from console)
4. Start threads
public class Client {
private final String host;
private final int port;
private boolean connected;
private Socket socket;
public Client(String host, int port) {
this.host = host;
this.port = port;
}
public void start() throws IOException {
connected = true;
socket = new Socket(host, port);
Runnable serverInputReader = () -> {
try (DataInputStream in = new DataInputStream(socket.getInputStream())) {
while (connected) {
String data = in.readUTF();
System.out.println(data);
}
} catch (IOException e) {
// problem connecting to server; problem wrapping stream; problem receiving data from server;
e.printStackTrace();
}
};
Runnable userInputReader = () -> {
try (DataOutputStream out = new DataOutputStream(socket.getOutputStream());
Scanner scanner = new Scanner(System.in)) {
while (connected) {
String input = scanner.nextLine();
out.writeUTF(input);
}
} catch (IOException e) {
//problem wrapping stream; problem sending data;
e.printStackTrace();
}
};
Thread communicateThread = new Thread(serverInputReader);
Thread userThread = new Thread(userInputReader);
communicateThread.start();
userThread.start();
}
public static void main(String[] args) throws IOException {
new Client("localhost", 15180).start();
}
}
There are a few things I used in the code above that you may not be familiar with. They help simplify the syntax for your code:
Lambda Expressions - Prevents the need to create an anonymous class (or subclass) to declare a method
Try-With-Resources - Closes the resources specified automatically once the try block as ended
EDIT
When a user connects, you should store their connection by name or id. That way, you can send data to specific users. Even if your client is running on the same machine as the server, it's still the same idea: client connects to server, server sends message to client based on name or id:
while(running) {
User client = new User(ss.accept());
users.add(client); //add to set
executor.execute(client);
}
Right now, you are simply adding users to a Set. There is currently no way to grab a specific value from this set. What you need to do is give it some kind of "key". To give you an idea, here's an old algorithm I used to use. I have an array full of empty slots. When someone connects, I look for the first empty slot. Once an empty slot is found, I pass the user the index of the array it's being stored at (that will be the user's id), then store the user in the array at the specified index. When you need to send a message to someone, you can use the id to access that specific array index, grab the user you want and send a message:
class Server {
private int maxConnections = 10;
private ExecutorService executor = Executors.newFixedThreadPool(maxConnections);
private User[] users = new User[maxConnections];
//...
while(running) {
Socket socket = ss.accept();
for(int i = 0; i < users.length; i++) {
if(users[i] == null) {
users[i] = new User(socket, i);
executor.execute(users[i]);
break;
}
}
}
//...
public static void sendGlobalMessage(String message) throws IOException {
for(User user : users)
if(user != null)
user.send(message);
}
public static void sendPrivateMessage(String message, int id) {
User user = users[id];
if(user != null) {
user.send(message);
}
}
}
class User {
private Socket socket;
private int id;
private DataOutputStream out;
public User(Socket socket, int id) {
this.socket = socket;
this.id = id;
}
public void send(String message) throws IOException {
out.writeUTF(message);
out.flush();
}
public void run() {
DataInputStream in;
//wrap in and out streams
while(connected) {
String data = in.readUTF();
//Server.sendGlobalMessage(data);
//Server.sendPrivateMessage(data, ...);
sendMessage(data); //sends message back to client
}
}
}

Handle more clients

Right now my server only can handle one client at a time. I am trying to use a Thread so that the server can handle several clients, but I am doing it wrong. I have added the thread in the try/catch clause where the serverSocket accepts the client, but this makes no difference. I don't get an error or anything, but it just doesn't work.
So what I want to do, is make the server not freeze at one client, but still accept several clients.
Here is the server code:
import java.io.*;
import java.net.*;
public class Server {
private BufferedReader reader;
private PrintWriter writer;
private int port;
public Server(int port)
{
this.port = port;
}
private String getSeverAddress() {
String host = null;
try {
InetAddress adr = InetAddress.getLocalHost();
host = adr.getHostAddress();
} catch (UnknownHostException e) {
e.printStackTrace();
}
return host;
}
public void startServer() {
print("Contact this sever on address: " + getSeverAddress() + " port: " + port);
ServerSocket ss = null;
Socket socket = null;
Thread clientThread = null;
try {
ss = new ServerSocket(port);
socket = ss.accept();
clientThread = new Thread(new Client(socket));
clientThread.start();
reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
writer = new PrintWriter(socket.getOutputStream(), true);
String msg = null;
while (( msg = reader.readLine()) != null) {
print("System out: " + msg);
if(msg.equals("Bye")) {
print("Client left");
break;
}
}
ss.close();
socket.close();
reader.close();
writer.close();
} catch(SocketException e) {
e.printStackTrace();
} catch (IOException i ) {
i.printStackTrace();
return;
}
}
private void print(String msg) {
System.out.println(msg);
}
public static void main(String[] args) {
Server server = new Server(1111);
server.startServer();
}
}
Here is the client code:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;
public class Client implements Runnable{
private Socket client;
private BufferedReader reader;
private PrintWriter writer;
public Client(Socket socket)
{
client = socket;
try{
reader = new BufferedReader(new InputStreamReader(client.getInputStream()));
writer = new PrintWriter(client.getOutputStream(), true);
} catch (Exception e) {
e.printStackTrace();
return;
}
}
#Override
public void run() {
String msg = null;
BufferedReader r = null;
try {
r = new BufferedReader(new InputStreamReader(System.in));
} catch (Exception e1) {
e1.printStackTrace();
}
System.out.println("Write message to server");
while(true) {
try {
msg = r.readLine();
if(msg.equals("Quit") || msg == null) {
print("Disconnect");
break;
}
} catch (IOException e) {
e.printStackTrace();
}
writeToServer(msg);
}
try {
r.close();
} catch (IOException e) {
e.printStackTrace();
}
}
public void writeToServer(String msg) {
writer.println(msg);
}
private void print(String msg) {
System.out.println(msg);
}
public static void main(String[] args) {
Socket socket = null;
try {
socket = new Socket("localhost", 1111);
} catch (Exception e) {
e.printStackTrace();
}
Client client = new Client(socket);
client.run();
}
}

You are still trying to handle clients in your main thread. Main thread should just accept new connections and start new threads. You also have to do accept in a loop so multiple connections can be accepted:
ss = new ServerSocket(port);
while(true) {
Socket socket = ss.accept();
Thread clientThread = new Thread(new Runnable() {
public void run() {
BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
PrintWriter writer = new PrintWriter(socket.getOutputStream(), true);
String msg = null;
while (( msg = reader.readLine()) != null) {
print("System out: " + msg);
if(msg.equals("Bye")) {
print("Client left");
break;
}
}
socket.close();
reader.close();
writer.close();
}});
clientThread.start();
}

You need to put your ss.accept() into a while loop and create a new Thread for every client accepted, which handles the connection.

How do i send the message to multiple clients in java Client-Server Program

Multiple Clients say(A, B, C, D etc) make connection to one server through same socket. They all send messages to server as and when required. Client messages are sent only to server(and not to other clients). But whenever server sends a message it should be delivered to all the clients. Please help me out jam only able to get server message on only 1 client
//MultithreadedServer.java
package server;
import java.io.*;
import java.net.*;
import java.util.ArrayList;
import java.util.Vector;
public class MultithreadedServer
{
Vector<ClientHandler> clients = new Vector<ClientHandler>();
Vector<String> users = new Vector<String>();
private static ServerSocket servSocket;
private static final int PORT = 1247;
public MultithreadedServer() throws IOException{
servSocket = new ServerSocket(PORT);
while(true) {
Socket client = servSocket.accept();
System.out.println("\nNew client accepted.\n");
ClientHandler handler;
handler = new ClientHandler(client);
clients.add(handler);
}
}
public static void main(String[] args) throws IOException
{
MultithreadedServer ms = new MultithreadedServer();
}
class ClientHandler extends Thread
{
private Socket client;
private BufferedReader in;
private PrintWriter out;
String name,message,response;
public ClientHandler(Socket socket)
{
//Set up reference to associated socket...
client = socket;
try
{
in = new BufferedReader(
new InputStreamReader(
client.getInputStream()));
out = new PrintWriter(
client.getOutputStream(),true);
}
catch(IOException e)
{
e.printStackTrace();
}
start();
}
public void sendMessage(String msg) {
System.out.println("is it even coming here?");
out.println("Server:" + msg);
}
public void boradcast(String message) {
// send message to all connected users
for (ClientHandler c : clients) {
c.out.println("Server: hello");
}
}
public String getUserName() {
return name;
}
public void run()
{
try
{
String received;
do
{ System.out.println("Enter Your Message: ");
String msg = in.readLine();
out.println(msg);
boradcast("testing");
received = in.readLine();
out.println("ECHO: " + received);
//Repeat above until 'QUIT' sent by client...
}while (!received.equals("QUIT"));
}
catch(IOException e)
{
e.printStackTrace();
}
finally
{
try
{
if (client!=null)
{
System.out.println(
"Closing down connection...");
client.close();
}
}catch(IOException e)
{
e.printStackTrace();
}
}
}
}}
//ClientProgram
import java.io.*;
import java.net.*;
public class Client
{
private static InetAddress host;
private static final int PORT = 1247;
private static Socket link;
private static BufferedReader in;
private static PrintWriter out;
private static BufferedReader keyboard;
public static void main(String[] args) throws IOException
{
try
{
host = InetAddress.getLocalHost();
link = new Socket(host, PORT);
in = new BufferedReader(
new InputStreamReader(
link.getInputStream()));
out = new PrintWriter(
link.getOutputStream(),true);
keyboard = new BufferedReader(
new InputStreamReader(System.in));
String message, response;
do
{
System.out.print(
"Enter message ('QUIT' to exit): ");
message = keyboard.readLine();
//Send message to server on
//the socket's output stream...
out.println(message);
//Accept response frm server on
//the socket's input stream...
response = in.readLine();
//Display server's response to user...
System.out.println(response);
}while (!message.equals("QUIT"));
}
catch(UnknownHostException uhEx)
{
System.out.println(
"\nHost ID not found!\n");
}
catch(IOException ioEx)
{
ioEx.printStackTrace();
}
finally
{
try
{
if (link!=null)
{
System.out.println(
"Closing down connection...");
link.close();
}
}
catch(IOException ioEx)
{
ioEx.printStackTrace();
}
}
}
}

An obvious way to do this would be to cycle through all ClientHandlers in clients and send the message to each of them:
for (ClientHandler ch : clients){
ch.sendMessage(message); //Or something
}