Socket Programming-Chat application in Java

So far we discussed about socket communication principles . Examples on TCP communication and UDP communication were also discussed. In this chapter we are discussing a console based(no GUI for this application) chat application in Java

Chat application in Java

It uses TCP socket communication .We have a server as well as a client.Both can be run in the same machine or different machines.If both are running in the machine , the adress to be given at the client side is local host address.If both are running in different machines , then in the client side we need to specify the ip address of machine in which server application is running.

Let us inspect the server code first.

The ChatSocketServer.java is the server application.It simply creates  a serverSocket on port 3339.Once a new connection comes , it accepts that connection and Socket object will be created for that connection.Now two threads will be created .One thread is for reading from the socket and the other is writing to socket.If the connection is terminated from client side , the server also exits.

ChatSocketServer.java

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;

public class ChatSocketServer {
private ServerSocket severSocket = null;
private Socket socket = null;
private InputStream inStream = null;
private OutputStream outStream = null;

public ChatSocketServer() {

}

public void createSocket() {
try {
ServerSocket serverSocket = new ServerSocket(3339);
while (true) {
socket = serverSocket.accept();
inStream = socket.getInputStream();
outStream = socket.getOutputStream();
System.out.println("Connected");
createReadThread();
createWriteThread();

}
} catch (IOException io) {
io.printStackTrace();
}
}

public void createReadThread() {
Thread readThread = new Thread() {
public void run() {
while (socket.isConnected()) {
try {
byte[] readBuffer = new byte[200];
int num = inStream.read(readBuffer);
if (num > 0) {
byte[] arrayBytes = new byte[num];
System.arraycopy(readBuffer, 0, arrayBytes, 0, num);
String recvedMessage = new String(arrayBytes, "UTF-8");
System.out.println("Received message :" + recvedMessage);
} else {
notify();
}
;
//System.arraycopy();

} catch (SocketException se) {
System.exit(0);

} catch (IOException i) {
i.printStackTrace();
}

}
}
};
readThread.setPriority(Thread.MAX_PRIORITY);
readThread.start();
}

public void createWriteThread() {
Thread writeThread = new Thread() {
public void run() {

while (socket.isConnected()) {
try {
BufferedReader inputReader = new BufferedReader(new InputStreamReader(System.in));
sleep(100);
String typedMessage = inputReader.readLine();
if (typedMessage != null && typedMessage.length() > 0) {
synchronized (socket) {
outStream.write(typedMessage.getBytes("UTF-8"));
sleep(100);
}
}/* else {
notify();
}*/
;
//System.arraycopy();

} catch (IOException i) {
i.printStackTrace();
} catch (InterruptedException ie) {
ie.printStackTrace();
}

}
}
};
writeThread.setPriority(Thread.MAX_PRIORITY);
writeThread.start();

}

public static void main(String[] args) {
ChatSocketServer chatServer = new ChatSocketServer();
chatServer.createSocket();

}
}

Now let us start  looking into the client side code.

The ChatSocketClient.java simply creates  socket  connection with the specified address on port  3339.Once a connection is established, two threads are creating.One for reading from the socket and other for writing to socket.Once the server disconnects the connection, the client exists itself.

ChatSocketClient.java

import java.io.*;
import java.net.Socket;
import java.net.SocketException;
import java.net.UnknownHostException;

public class ChatSocketClient {
private Socket socket = null;
private InputStream inStream = null;
private OutputStream outStream = null;

public ChatSocketClient() {

}

public void createSocket() {
try {
socket = new Socket("localHost", 3339);
System.out.println("Connected");
inStream = socket.getInputStream();
outStream = socket.getOutputStream();
createReadThread();
createWriteThread();
} catch (UnknownHostException u) {
u.printStackTrace();
} catch (IOException io) {
io.printStackTrace();
}
}

public void createReadThread() {
Thread readThread = new Thread() {
public void run() {
while (socket.isConnected()) {

try {
byte[] readBuffer = new byte[200];
int num = inStream.read(readBuffer);

if (num > 0) {
byte[] arrayBytes = new byte[num];
System.arraycopy(readBuffer, 0, arrayBytes, 0, num);
String recvedMessage = new String(arrayBytes, "UTF-8");
System.out.println("Received message :" + recvedMessage);
}/* else {
// notify();
}*/
;
//System.arraycopy();
}catch (SocketException se){
System.exit(0);

} catch (IOException i) {
i.printStackTrace();
}

}
}
};
readThread.setPriority(Thread.MAX_PRIORITY);
readThread.start();
}

public void createWriteThread() {
Thread writeThread = new Thread() {
public void run() {
while (socket.isConnected()) {

try {
BufferedReader inputReader = new BufferedReader(new InputStreamReader(System.in));
sleep(100);
String typedMessage = inputReader.readLine();
if (typedMessage != null && typedMessage.length() > 0) {
synchronized (socket) {
outStream.write(typedMessage.getBytes("UTF-8"));
sleep(100);
}
}
;
//System.arraycopy();

} catch (IOException i) {
i.printStackTrace();
} catch (InterruptedException ie) {
ie.printStackTrace();
}

}
}
};
writeThread.setPriority(Thread.MAX_PRIORITY);
writeThread.start();
}

public static void main(String[] args) throws Exception {
ChatSocketClient myChatClient = new ChatSocketClient();
myChatClient.createSocket();
/*myChatClient.createReadThread();
myChatClient.createWriteThread();*/
}
}

Output

Run the ChatSocketServer.java and then the ChatSocketClient.java.Once both hot connected, connected message will be displayed on the console.Now type messages on each console and press enter button.Messages will be transmitted throgh socket.

Output of ChatSocketServer.java

Connected

Received message :haai

I am server

who are u ?

Received message :i am client …How r u ?

Output of ChatSocketClient,java

Connected

haai

Received message :I am server

Received message :who are u ?

i am client …How r u ?

See related topics:

Networking with Java – overview

TCP communication with Java

UDP communication with Java

17 thoughts on “Socket Programming-Chat application in Java

  1. excuse me i want to know how can i connect these client and severs in a form i java to make it graphical?

    • I think you are trying to make GUI for this app. For that you can enhance this application using GUI techniques like Swing

    • Hi Nahid,
      Did you get the solution for the same , where u can use the things with form . If yes please share your experience. We are wondering for the same.

  2. thanx dude…!! it really worked without any error..!!!

  3. shivakumar says:

    Thanks a lot for giving valuable and working code.. 🙂

  4. I’m trying to use your code to connect to a VB.NET socket program. Everything works good but for some reason if I send a text shorter than the previous text it shows text from the previous one sent.

    Java Send TEST12345
    VB Recv TEST12345
    Java Send 12
    VB Recv 12ST12345

    I’ve looked at both sides. Java says it’s only sending 12 and VB is null because the receive but when it receives it gets 12ST12345. Any ideas? I’ve tried flushing the buffer on the java side.

    It seems to work fine for VB to VB.

  5. please give the code many clients displaying their ip address , to the server.peer to peer communication concept ,and distributed concept

  6. java.net.ConnectException: Connection refused: ??

  7. Awesome Code..Runs without error

  8. Sir,please tell how to run the code in two different machines?

  9. Its a good code Sir.
    I was actually hoping for multiple users/clients interacting to each other via a common server.

  10. Hi~~Me again 🙂
    Thanks a lot!
    But when I put this program and transfer file program together
    Error came
    say:java.net.ConnectException: Connection refused: connect
    I used search engine but still cannot work it out
    Can you help me at your convenience?
    Thanks a lot! 🙂

  11. hey its not working for group chat
    what should be done??

  12. Awesome work..

    Very helpful.

    Thanks.

  13. Hey, on occasion I get a 503 server error when I browse your webpage. I thought you may wish to know, regards

  14. thanks. it works and its easy to understand

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