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How can a server broadcast a message to other clients?

The program is intended to have multiple clients connect to a single server and the clients are able to send and receive messages among other clients.
For example if Client A says "Hi", Client B and Client C connected to the server would also receive "Hi".
In my current code, the server only receives the messages sent by the clients.
I'm currently looking for a solution to have the server broadcast the message sent by a client (eg. ClientA) to other clients. Any advice would be much appreciated.
This server class handles the connections of multiple clients with the use of threads:
import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
class EchoThread extends Thread {
private Socket socket;
//constructor
public EchoThread(Socket clientSocket) {
this.socket = clientSocket;
}
#Override
public void run() {
DataInputStream inp = null;
try {
inp = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
//print whatever client is saying as long as it is not "Over"
String line = "";
while (!line.equals("Over")) {
try {
line = inp.readUTF();
System.out.println(line);
} catch (IOException e) { System.out.println(e); }
}
//closes connection when client terminates the connection
System.out.print("Closing Connection");
socket.close();
} catch (IOException e) { System.out.println(e); }
}
}
public class Server {
private static final int PORT = 5000;
public static void main(String args[]) {
ServerSocket serverSocket = null;
Socket socket = null;
//starts the server
try {
serverSocket = new ServerSocket(PORT);
System.out.println("Server started");
System.out.println("Waiting for a client ...\n");
} catch (IOException e) { System.out.println(e); }
//while loop to accept multiple clients
int count = 1;
while(true) {
try {
socket = serverSocket.accept();
System.out.println("Client " + count + " accepted!");
count++;
} catch (IOException e) { System.out.println(e); }
//starts the server thread
new EchoThread(socket).start();
}
}
}
and this is the client class (I have multiple instances of this code running):
import java.net.*;
import java.io.*;
public class ClientA {
private Socket socket = null;
private DataInputStream input = null;
private DataOutputStream output = null;
public ClientA(String address, int port) {
//establish connection
try {
socket = new Socket(address, port);
System.out.println("Connected");
//takes input from terminal
input = new DataInputStream(System.in);
//sends output to the socket
output = new DataOutputStream(socket.getOutputStream());
} catch (IOException e) { System.out.println(e); }
//string to read message from input
String line = "";
//keep reading until "Over" is input
while (!line.equals("Over")) {
try {
line = input.readLine();
output.writeUTF(line);
} catch (IOException e) { System.out.println(e); }
}
//close the connection
try {
input.close();
output.close();
socket.close();
} catch (IOException e) { System.out.println(e); }
}
public static void main (String args[]) {
ClientA client = new ClientA("127.0.0.1", 5000);
}
}
Do feel free to correct me on my code comments as I'm still not very familiar with socket programming.

You did well. Just add a thread to receive message in ClientA; and store socket clients in Server.
In fact, Server is also a "client" when is send message to client.
I add some code based on your code. It works well, hope it's helpful.
class EchoThread extends Thread {
//*****What I add begin.
private static List<Socket> socketList = new ArrayList<>();
//*****What I add end.
private Socket socket;
//constructor
public EchoThread(Socket clientSocket) {
this.socket = clientSocket;
socketList.add(socket);
}
#Override
public void run() {
DataInputStream inp = null;
try {
inp = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
//print whatever client is saying as long as it is not "Over"
String line = "";
while (!line.equals("Over")) {
try {
line = inp.readUTF();
System.out.println(line);
//*****What I add begin.
sendMessageToClients(line);
//*****What I add end.
} catch (IOException e) { System.out.println(e); break;}
}
//closes connection when client terminates the connection
System.out.print("Closing Connection");
socket.close();
} catch (IOException e) { System.out.println(e); }
}
//*****What I add begin.
private void sendMessageToClients(String line) throws IOException {
for (Socket other : socketList) {
if (other == socket) {
continue;//ignore the sender client.
}
DataOutputStream output = new DataOutputStream(other.getOutputStream());
output.writeUTF(line);
}
}
//*****What I add end.
}
public class ClientA {
private Socket socket = null;
private DataInputStream input = null;
private DataOutputStream output = null;
public ClientA(String address, int port) {
//establish connection
try {
socket = new Socket(address, port);
System.out.println("Connected");
//takes input from terminal
input = new DataInputStream(System.in);
//sends output to the socket
output = new DataOutputStream(socket.getOutputStream());
//*****What I add begin.
//Here create a thread to receive message from server.
DataInputStream inp = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
new Thread(() -> {
while (true) {
String str;
try {
str = inp.readUTF();
System.out.println(str);
} catch (IOException e) {
e.printStackTrace();//error.
break;
}
}
}, "Client Reveiver.").start();
//*****What I add end.
} catch (IOException e) { System.out.println(e); }
//string to read message from input
String line = "";
//keep reading until "Over" is input
while (!line.equals("Over")) {
try {
line = input.readLine();
output.writeUTF(line);
} catch (IOException e) { System.out.println(e); }
}
//close the connection
try {
input.close();
output.close();
socket.close();
} catch (IOException e) { System.out.println(e); }
}

I would have a single server thread which would maintain a register of the clients, possibly in a concurrent collection. Then I would send each message received from a client to all other clients.

Server is not sending back an acknowledgment to Client

I have my server code below over here:
public void startServer() {
ServerSocket listener = selectUnusedPortFromRange(1024, 65535);
Thread t = new Thread(new Runnable() {
#Override
public void run() {
try {
String command = null;
while (true) {
Socket socket = listener.accept();
System.out.println("Got a connection from: " + socket.getLocalPort());
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
command = in.readLine();
System.out.println("GOT HERE"); //Not being printed out
if (command != null && !"".equals(command)) {
if ("connection".equals(command)) {
Writer writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
writer.write("success\n");
writer.flush();
}
}
}
}
}
}
t.start();
}
This is my client side:
public void makeConnection() {
try {
Socket socket = new Socket(IP, PORT);
Writer writer = new PrintWriter(socket.getOutputStream(), true);
writer.write("connection\n");
BufferedReader socketRead = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String str;
while ((str = socketRead.readLine()) != null) {
if ("success".equals(str)) {
System.out.println("Successfully saved all hosts to: " + listOfHosts.get(i));
socketRead.close();
socket.close();
iStream.close();
writer.close();
}
}
}catch (Exception e) {
System.out.println(e.getMessage());
}
}
On the client side after I create my socket to the connect to the server I write "connection" into the outputStream of the socket and wait for an acknowledgement back from the server saying success. For some reason the connection is not being made to the server. In the server System.out.println("Got a connection from: " + socket.getLocalPort()); this line is not being printed out.
Is there something wrong that I am doing. I can't spot it. And I am not getting an exception thrown when I try to connect to my server.

1) Make sure you use the same port for both the Client and Server. They must communicate over the same port. It seems you may be using different ports currently.
2) Make sure you actually start your server thread. As-is in your code above, you make a new Thread, but never start it. t.start() must be called somewhere.
3) If this is on your local machine, you may be better off using localhost instead of the actual IP address. Firewalls might treat your external IP differently.
4) Terminate your messages with a newline character, such as \n, so that your BufferedReader can use it's readLine() method. For good measure, also follow-up by flushing the writer's buffer, just in case the newline character didn't trigger that. writer.flush();
And lastly, make sure you terminate the JVM before trying to run your code again. Your code has not shutdown mechanism to un-bind the server from the port... so you may get an exception thrown telling you the port and/or address are already in use. If that happens, either change ports, or kill the java process running in the background.
Here is your code, slightly modified to run on my system. It's working as you might expect it to. I tried to change as little as possible just to get it working on my system. One note is, I hard-coded the port number into the server and client - that's not required, it was just convenient for me to test with:
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Writer;
import java.net.ServerSocket;
import java.net.Socket;
public class Test {
public static void main(String[] args) throws IOException {
Test test = new Test();
test.startServer();
test.makeConnection();
}
public void startServer() throws IOException {
final ServerSocket listener = new ServerSocket(60001);
Thread t = new Thread(new Runnable() {
#Override
public void run() {
try {
String command = null;
while (true) {
Socket socket = listener.accept();
System.out.println("Got a connection from: " + socket.getLocalPort());
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
command = in.readLine();
System.out.println("GOT HERE");
if (command != null && !"".equals(command)) {
if ("connection".equals(command)) {
Writer writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
writer.write("success\n");
writer.flush();
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
});
t.start();
}
public void makeConnection() {
System.out.println("Making Connection");;
try {
Socket socket = new Socket("localhost", 60001);
Writer writer = new PrintWriter(socket.getOutputStream(), true);
writer.write("connection\n");
writer.flush();
BufferedReader socketRead = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String str;
while ((str = socketRead.readLine()) != null) {
if ("success".equals(str)) {
System.out.println("Successfully saved all hosts to: "); //+ listOfHosts.get(i));
socketRead.close();
socket.close();
//iStream.close();
writer.close();
}
}
}catch (Exception e) {
System.out.println(e.getMessage());
}
}
}

I was facing the exact same issue. I overcame it by using an ACK mechanism (Wasn't my idea, it was suggested to me). The idea is that client would make a request to server and keep the socket connection alive (and the ouput stream open) till server responds back an agreed ACK message over the same channel. Once the client receives the ACK message, only then it would close the connection.
Below is the code for Server :-
final ServerSocket listener = new ServerSocket(11111);
Thread t = new Thread(new Runnable() {
#Override
public void run() {
try {
String command = null;
while (true) {
System.out.println("About to accept");
Socket socket = listener.accept();
System.out.println("Got a connection from: " + socket.getLocalPort());
DataInputStream inputStream = new DataInputStream(socket.getInputStream());
StringBuilder str = new StringBuilder(inputStream.readUTF());
//command = in.readLine();
System.out.println("GOT HERE. Msg received : "+str);
if (str != null && !"".equals(str.toString())) {
command = str.toString();
if ("connection".equals(command)) {
System.out.println("Got connection message");
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
outputStream.writeUTF("connection");
outputStream.close();
}
}
inputStream.close();
System.out.println("Done");
}
} catch (IOException e) {
e.printStackTrace();
} finally {
}
}
});
t.start();
}
Client :-
public void makeConnection() {
try {
System.out.println("In makeConnection");
Socket socket = new Socket("127.0.0.1", 11111);
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
outputStream.writeUTF("connection");
InputStream inputStream = socket.getInputStream();
DataInputStream dataInputStream = new DataInputStream(inputStream);
StringBuilder str;
do {
str = new StringBuilder(dataInputStream.readUTF());
} while (!str.toString().equals("connection"));
System.out.println("Successfully saved all hosts to: ");
outputStream.close();
dataInputStream.close();
socket.close();
outputStream.close();
}catch (Exception e) {
System.out.println(e.getMessage());
}
}
A call to start the proceedings :-
public void start() throws IOException, InterruptedException {
System.out.println("Starting server");
startServer();
Thread.sleep(1000);
System.out.println("Starting connection");
makeConnection();
}

How to broadcast messages to all clients using tcp in java

I am building a multithreaded chat server application which broadcasts a message sent by one client to all the clients.On most of the examples on internet and on Oracle's website too broadcasting is done using udp (Multicast Socket)but i am using tcp .
Does anyone know how to send a message to all the connected clients in a tcp conection?
Here is my current code which works fine and sends the message receieved from a client to that client only:
EchoServer
import java.net.*;
import java.io.*;
public class EchoServer
{
public static void main(String[] args)
throws IOException
{
if (args.length != 1) {
System.err.println("Usage: java EchoServer <port number>");
System.exit(1);
}
int portNumber = Integer.parseInt(args[0]);
ServerSocket serverSocket = new ServerSocket(Integer.parseInt(args[0]));
while (true) {
try {
Thread t = new Thread(new MultiServer(serverSocket.accept()));
t.start();
} catch(IOException e) {
System.out.println("Accept Failed:");
System.exit(-1);
}
}
}
}
EchoClient
import java.io.*;
import java.util.Scanner;
import java.net.*;
public class EchoClient
{
public static void main(String[] args) throws IOException
{
if (args.length != 2) {
System.err.println("Usage: java EchoClient <host name><portnumber>");
System.exit(1);
}
String hostName = "localhost";
int portNumber = Integer.parseInt(args[1]);
try (
Socket echoSocket = new Socket(hostName, portNumber);
PrintWriter out = new PrintWriter(echoSocket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(echoSocket.getInputStream()));
BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));
) {
String userInput;
while ((userInput = stdIn.readLine()) != null) {
out.println(userInput);
System.out.println("echo::" + in.readLine());
}
} catch (UnknownHostException e) {
System.err.println("Don't know about host " + hostName);
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to " + hostName);
System.exit(1);
}
}
}
MultiServer
import java.io.*;
import java.net.*;
public class MultiServer implements Runnable
{
private Socket client;
public MultiServer(Socket m)
{
this.client = m;
}
#Override
public void run()
{
BufferedReader in = null;
PrintWriter out = null;
try {
out = new PrintWriter(client.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(client.getInputStream()));
} catch(IOException ignored) {
}
while (true) {
String line;
try {
while ((line = in.readLine()) != null)
out.println(line);
} catch (IOException e) {
System.out.println("Read Failed");
System.exit(-1);
}
}
}
}

Use the concurrent hashmap and maintain your list of clients in that.
The concurrent hashmap is safe and you won't need to use synchronization while adding / iterating / removing
// Create and main list of active clients based on their host name / ip address
ConcurrentHashMap<String, Socket> activeClients = new ConcurrentHashMap<String, Socket>();
// message received
activeClients.put(clientsocket.getInetAddress().getHostAddress(), clientsocket);
// broadcast message to all available clients
for(String clientHost : activeClients.keySet()) {
// get each socket here and send a message to them.
}
Vector is basically a thread safe one so you don't need to worry about that one.

Application Hangs over the socket, Unable to read client data at server side

I am trying to implement a client server socket connection where i am passing commands like ls/pwd over the GUI and I use an url(localhost) to establish the server connection at the port. Although i am able to establish a connection with client ,the code does not proceed beyond the Client Connection accepted state. I.e. it does not read the input at the server end which was sent by the client over the socket. Below are my three classes, Mainserver, ClientHandler(this handles the thread connections for the server)and the Client.
This is the Client Action button performed code:
private void jButton1ActionPerformed(java.awt.event.ActionEventevt) {
command = jTextField1.getText();
String url = jTextField3.getText();
try {
System.out.println("Before socket connection");
Socket socket = new Socket(url, 9002);
System.out.println("After socket connection");
PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
System.out.println("After Buffered readers");
System.out.println("After getting streams");
if (socket != null) {
try {
int x = Integer.parseInt(command);
flag = 1;
} catch (Exception e) {
flag = 0;
}
if (flag == 0) {
String[] cmd = {"/bin/sh", "-c", command};
System.out.println("the value of command in GUI class is " + Arrays.toString(cmd));
try {
String commd = Arrays.toString(cmd);
System.out.println(commd);
out.write(commd);
input = in.readLine();
}
catch (IOException ex1)
{
Logger.getLogger(TestGUI.class.getName()).log(Level.SEVERE, null, ex1);
}
jTextField2.setText(input.toString());
}
}
}//try end of the first one
catch (IOException ex) {
Logger.getLogger(TestGUI.class.getName()).log(Level.SEVERE, null, ex);
}
The server class:
public class ServerMain {
public static void main(String[] args) throws IOException, InterruptedException {
int number, temp;
try {
ServerSocket serverSocket = new ServerSocket(9002);
System.out.println("server has been started in the server");
System.out.println("Server is waiting connection at" + InetAddress.getLocalHost().getCanonicalHostName() + "port" + serverSocket.getLocalPort());
while (true) {
Socket socket = serverSocket.accept();
System.out.println("Client Connection Accepted");
//pass on handling on this client to a thread
(new ClientHandler(socket)).start();
}
} catch (Exception e) {
System.err.println("Server already in use");
System.exit(-1);
}
}
}
The client Handler for the Server:
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.logging.Level;
import java.util.logging.Logger;
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
/**
*
* #author ameerah
*/
public class ClientHandler extends Thread {
private static int BUFSIZE = 1024;
private StringBuffer result;
ServerSocket serverSocket;
String serverText;
StringBuffer output = new StringBuffer();
private Object serversocket;
public Socket getSock() {
return sock;
}
public void setSock(Socket sock) {
this.sock = sock;
}
Socket sock;
public ClientHandler(Socket sock) {
this.sock = sock;
}
#Override
public void run() {
PrintWriter outWriter = null;
try {
BufferedReader myInput = new BufferedReader(new InputStreamReader(sock.getInputStream()));
outWriter = new PrintWriter(sock.getOutputStream());
System.out.println(
"before accepting the command in server");
String inputLine;
while ((inputLine = myInput.readLine()) != null) //String command = myInput.readLine();
{
System.out.println(inputLine);
String result = "";
try {
result = executeCommand(inputLine);
} catch (IOException ex) {
Logger.getLogger(ClientHandler.class.getName()).log(Level.SEVERE, null, ex);
} catch (InterruptedException ex) {
Logger.getLogger(ClientHandler.class.getName()).log(Level.SEVERE, null, ex);
}
System.out.println(result);
outWriter.write(result);
}
} catch (IOException ex) {
Logger.getLogger(ClientHandler.class.getName()).log(Level.SEVERE, null, ex);
} finally {
outWriter.close();
}
}
public String executeCommand(String cmd)
throws IOException, InterruptedException {
try {
Process p = Runtime.getRuntime().exec(cmd);
p.waitFor();
BufferedReader reader
= new BufferedReader(new InputStreamReader(p.getInputStream()));
System.out.println("Inside the execute method");
String line = "";
while ((line = reader.readLine()) != null) {
output.append(line + "\n");
}
} catch (Exception e) {
e.printStackTrace();
}
return output.toString();
}
}
I have been at it for some time, and tried using different streams such as ObjectInputStream, ObjectOutputStream, but the code hangs each time. I cannot see at this point where Im going wrong :( I've searched in several forums but I do not still get an idea where Im going wrong here.Would appreciate any help.!
Best Regards

It was the readLine() which was expecting '\n' at the end. Therefore once i appended '\n' at the end and added out.flush() it was able to read and not keep hanging waiting for more inputs, and now the application is working.
Thank you very much for your helpful suggestions. The out.flush() advice proved to be very helpful.

Few tips to isolate the problem.
Check the value of command and catch Exception stack trace.
After out.write(commd); : add one more line out.flush(); After flush, server will get the data from client. Same is the case with outWriter. flush() should be called on outWriter after writing the data.

You are looking for an end of line to end your input loop but you are using write.
Change your send data statements to use println.
Client:
out.println(commd);
Server:
outWriter.println(result);

BufferedReader from server does not work

In this code I can correctly receive a request using BufferedReader inClient, created on the client socket.
Then I send the request to the server and I see the server gets it.
But then, when I try to read the reply from the server (using BufferedReader inServer on the socket of the server), it always ends in IOException: Impossible read from server.
I am referring to the block ################
Do you know any possible reasons?
import java.io.*;
import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetAddress;
import java.net.UnknownHostException;
public class ProxyMain {
public static void main(String argv[]) {
int proxyPort = 55554;
String proxyAddr = "127.0.0.1";
ServerSocket proxySocket = null;
try {
proxySocket = new ServerSocket(proxyPort, 50, InetAddress.getByName("127.0.0.1"));
}
catch (Exception e) {
System.err.println("Impossible to create socket server!");
System.out.flush();
System.exit(1);
}
System.out.printf("Proxy active on port: %d and on address %s\n", proxyPort, proxySocket.getInetAddress());
System.out.println();
while (true) {
Socket client = null;
Socket sockServ = null;
BufferedReader inClient = null;
PrintWriter outClient = null;
BufferedReader inServer = null;
PrintWriter outServer = null;
String request = new String();
String tmp = new String();
String reply = new String();
String tmpReply = new String();
try {
client = proxySocket.accept();
System.out.println("Connected to: ");
System.out.println(client.getInetAddress().toString());
System.out.printf("On port %d\n", client.getPort());
System.out.println();
inClient = new BufferedReader(new InputStreamReader(client.getInputStream()));
outClient = new PrintWriter(client.getOutputStream(), true);
}
/*catch (IOException e) {
System.err.println("Couldn't get I/O for connection accepted");
System.exit(1);
}*/
catch (Exception e) {
System.out.println("Error occurred!");
System.exit(1);
}
System.out.println("Received request:");
try{
for (int i = 0; i<2; i++) {
tmp = inClient.readLine();
request = request + tmp;
}
inClient.close();
}
catch (IOException ioe) {
System.err.println("Impossible to read mhttp request!");
System.exit(1);
}
System.out.println(request);
System.out.println();
try {
sockServ = new Socket("127.0.0.1", 55555);
outServer = new PrintWriter(sockServ.getOutputStream(), true);
inServer = new BufferedReader(new InputStreamReader(sockServ.getInputStream()));
}
catch (UnknownHostException e) {
System.err.println("Don't know about host: 127.0.0.1:55555");
System.exit(1);
}
catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to: 127.0.0.1:55555");
System.exit(1);
}
outServer.println(request);
outServer.close();
try {
#################################################
while ((tmpReply = inServer.readLine()) != null) {
System.out.println(tmpReply);
reply = reply + tmpReply;
}
inServer.close();
sockServ.close();
}
catch (IOException ioe) {
System.err.println("Impossible to read from server!");
System.exit(1);
}
outClient.println(reply);
outClient.close();
try {
client.close();
}
catch (IOException ioe) {
System.err.printf("Impossible to close connection with %s:%d\n", client.getInetAddress().toString(), client.getPort());
}
}
}
}
UPDATE:
It seems that if I do:
boolean res = inServer.ready();
it always return false.
So Server is not ready to send the reply but this is strange...with my Project in C e Python it worked immediately. Why should java be different?

When you close outServer, you close the underlying socket. if you just want to close the output and keep the input open, you need to use Socket.shutdownOutput(). note, you have the same problem when you close inClient.

This works, maybe you can get some ideas from it...
ChatServer - broadcasts to all connected clients
In one command prompt: java ChartServer
In another: java ChatClient localhost (or the ip address of where the server is running)
And another: java ChatClient localhost (or the ip address of where the server is running)
Start chatting in the client windows.
Server like this...
// xagyg wrote this, but you can copy it
import java.io.*;
import java.net.*;
import java.util.*;
public class ChatServer {
public static List list = new ArrayList();
public static void main(String[] args) throws Exception {
ServerSocket svr = new ServerSocket(4444);
System.out.println("Chat Server started!");
while (true) {
try {
Socket s = svr.accept();
synchronized(list) {
list.add(s);
}
new Handler(s, list).start();
}
catch (IOException e) {
// print out the error, but continue!
System.err.println(e);
}
}
}
}
class Handler extends Thread {
private Socket s;
private String ipaddress;
private List list;
Handler (Socket s, List list) throws Exception {
this.s = s;
ipaddress = s.getInetAddress().toString();
this.list = list;
}
public void run () {
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(s.getInputStream()));
String message;
//MyDialog x = (MyDialog)map.get(ipaddress.substring(1));
while ((message = reader.readLine()) != null) {
if (message.equals("quit")) {
synchronized(list) {
list.remove(s);
}
break;
}
synchronized(list) {
for (Object object: list) {
Socket socket = (Socket)object;
if (socket==s) continue;
PrintWriter writer = new PrintWriter(socket.getOutputStream());
writer.println(ipaddress + ": " + message);
writer.flush();
}
}
}
try { reader.close(); } catch (Exception e) {}
}
catch (Exception e) {
System.err.println(e);
}
}
}
Client like this ...
// xagyg wrote this, but you can copy it
import java.util.*;
import java.io.*;
import java.net.*;
public class ChatClient {
public static void main(String[] args) throws Exception {
Socket s = new Socket(args[0], 4444);
BufferedReader in = new BufferedReader(new InputStreamReader(s.getInputStream()));
PrintWriter out = new PrintWriter(s.getOutputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String message;
new SocketReader(in).start();
while ((message = reader.readLine())!=null) {
out.println(message);
out.flush();
if (message.equals("quit")) break;
}
in.close();
out.close();
}
}
class SocketReader extends Thread {
BufferedReader in;
public SocketReader(BufferedReader in) {
this.in = in;
}
public void run() {
String message;
try {
while ((message = in.readLine())!=null) {
System.out.println(message);
}
}
catch (Exception e) {
throw new RuntimeException(e);
}
}
}