Client and Server Message exchange JAVA

In this blog post i will be providing a simple program and its explanation about the Client and server communication using sockets in JAVA. We are going to use 2 streams (Input and Output) for the client and for server to read and write data from and to console.

We will create client.java which opens a socket using hostname and port and talk to server using the Input and output streams. And then we will create Server.java and create a server socket using the same port and read message from client input stream and write the modified message to client output stream.


                 


Below is the program for Client and Server message exchange.

Client.java

public class Client {

    public static void main(String args[]){

        try {

            String host = "localhost";

            int port = 1200;

            Socket socket = new Socket(host, port);

            

            //Open the output stream of client to write the message.

            OutputStream osClient = socket.getOutputStream();

            OutputStreamWriter sw = new                OutputStreamWriter(osClient);

            BufferedWriter bw = new BufferedWriter(sw);

            //Take input from user ie message to be sent to server

            BufferedReader brClient = new BufferedReader(new InputStreamReader(System.in));

            String strClient = brClient.readLine();

            String sendMessage = strClient + "\n";

            bw.write(sendMessage);

            bw.flush();

            System.out.println("Message sent to the server : "+sendMessage);

            //Get the return message from the server by opening input stream of server and reading it.

            InputStream isServer = socket.getInputStream();

            InputStreamReader isr = new InputStreamReader(isServer);

            BufferedReader br = new BufferedReader(isr);

            String message = br.readLine();

            System.out.println("Message received from the server : " +message);

            socket.close();

        }catch (IOException e){

           e.printStackTrace();

        }

    }

}

Server.java

public class Server {

    private static Socket socket;

    public static void main(String[] args)

    {

        try

        {

            int port = 1200;

           // Create Server socket using the port.

            ServerSocket serverSocket = new ServerSocket(port);

            System.out.println("Server Started and listening to the port 1200");

            //Server is running always

            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 message = br.readLine();

                System.out.println("Message received from client is "+message);

                //Modify the message received from client by appending "From server" string

                String returnMessage;

                try

                {

                    String modifiedMessage = message + "From server";

                   

                    returnMessage = String.valueOf(modifiedMessage) + "\n";

                }

                catch(NumberFormatException e)

                {

                    //Input was not a String. Sending proper message back to client.

                    returnMessage = "Please send a proper message in string format\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();

        }

    }

}