Java Example - ServerSocket and Socket Communication Example

Java Examples

The following example demonstrates how to implement a client sending a message to a server, the server receiving and reading the message, and then sending it back to the client who receives the output.

1. Set up the server side

Establish communication with ServerSocket
Set up a Socket to receive client connections
Create an IO input stream to read data sent by the client
Create an IO output stream to send data messages to the client

Server-side code:

Server.java File

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
   public static void main(String[] args) {
      try {
         ServerSocket ss = new ServerSocket(8888);
         System.out.println("Starting server....");
         Socket s = ss.accept();
         System.out.println("Client:" + s.getInetAddress().getLocalHost() + " has connected to the server");

         BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
         // Read the message sent by the client
         String mess = br.readLine();
         System.out.println("Client: " + mess);
         BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
         bw.write(mess + "\n");
         bw.flush();
      } catch (IOException e) {
         e.printStackTrace();
      }
   }
}

The output of the above code is:

Starting server....

2. Set up the client side

Create a Socket for communication, set the IP and Port of the server
Create an IO output stream to send data messages to the server
Create an IO input stream to read data messages sent by the server

Client-side code:

Client.java File

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class Client {
   public static void main(String[] args) {
      try {
         Socket s = new Socket("127.0.0.1", 8888);

         // Build IO
         InputStream is = s.getInputStream();
         OutputStream os = s.getOutputStream();

         BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os));
         // Send a message to the server
         bw.write("Testing client-server communication, server receives message and returns it to client\n");
         bw.flush();

         // Read the message returned by the server

BufferedReader br = new BufferedReader(new InputStreamReader(is)); String mess = br.readLine(); System.out.println("Server: " + mess); } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } }

The above code outputs:

Server: Testing client-server communication, the server receives the message and returns it to the client

Java Examples

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