[SOLVED] Java Socket Example for sending and receiving byte array


Welcome again to my blog! A lot of people have asked me to share a working example of sending and receiving byte array using Java socket programming. So, below is an example for you to get started:
Server.java

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// A Java program for a Server 
import java.net.*;
import java.util.Arrays;
import java.io.*; 

public class Server 
{ 
 //initialize socket and input stream 
 private Socket   socket = null; 
 private ServerSocket server = null; 
 private InputStream in  = null; 
 private OutputStream out = null;

 // constructor with port 
 public Server(int port) 
 { 
  // starts server and waits for a connection 
  try
  { 
   server = new ServerSocket(port); 
   System.out.println("Server started"); 

   System.out.println("Waiting for a client ..."); 

   socket = server.accept(); 

   System.out.println("Client accepted"); 

   // takes input from the client socket 
   in = new DataInputStream(socket.getInputStream()); 
   //writes on client socket
   out = new DataOutputStream(socket.getOutputStream());

   // Receiving data from client
   ByteArrayOutputStream baos = new ByteArrayOutputStream();
   byte buffer[] = new byte[1024];
   baos.write(buffer, 0 , in.read(buffer));
   
   byte result[] = baos.toByteArray();

   String res = Arrays.toString(result);
   System.out.println("Recieved from client : "+res); 
   
   //echoing back to client
   out.write(result);
   
   System.out.println("Closing connection"); 

   // close connection 
   socket.close(); 
   in.close(); 
  } 
  catch(IOException i) 
  { 
   System.out.println(i); 
  } 
 } 

 public static void main(String args[]) 
 { 
  new Server(5000); 
 } 
}

Client.java

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// A Java program for a Client 
import java.net.*;
import java.util.Arrays;
import java.io.*;

public class Client {
 // initialize socket and input output streams
 private Socket socket = null;
 private OutputStream out = null;
 private InputStream in = null;

 // constructor to put ip address and port
 public Client(String address, int port) {
  // establish a connection
  try {
   socket = new Socket(address, port);
   if (socket.isConnected()) {
    System.out.println("Connected");
   }

   // sends output to the socket
   out = new DataOutputStream(socket.getOutputStream());
   //takes input from socket
   in = new DataInputStream(socket.getInputStream());
  } catch (UnknownHostException u) {
   System.out.println(u);
  } catch (IOException i) {
   System.out.println(i);
  }

  
  try {
   byte[] arr = {(byte)0x00, (byte)0x01, (byte)0x00, (byte)0x10, (byte)0x00, (byte)0x01,
       (byte)0x00, (byte)0x1F, (byte)0x60, (byte)0x1D, (byte)0xA1, (byte)0x09,
       (byte)0x06, (byte)0x07, (byte)0x60, (byte) 0x85, (byte)0x74, (byte)0x05,
       (byte) 0x08, (byte)0x01, (byte)0x01, (byte)0xBE, (byte)0x10, (byte)0x04,
       (byte)0x0E, (byte)0x01, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x06,
       (byte)0x5F, (byte)0x1F, (byte)0x04, (byte)0x00, (byte)0x00, (byte)0x18,
       (byte)0x1D, (byte)0xFF, (byte)0xFF};

   // sending data to server
   out.write(arr);

   String req = Arrays.toString(arr);
   //printing request to console
   System.out.println("Sent to server : " + req);

   // Receiving reply from server
   ByteArrayOutputStream baos = new ByteArrayOutputStream();
   byte buffer[] = new byte[1024];
   baos.write(buffer, 0 , in.read(buffer));
   
   byte result[] = baos.toByteArray();

   String res = Arrays.toString(result);

   // printing reply to console
   System.out.println("Recieved from server : " + res);
  } catch (IOException i) {
   System.out.println(i);
  }
  // }

  // close the connection
  try {
   // input.close();
   in.close();
   out.close();
   socket.close();
  } catch (IOException i) {
   System.out.println(i);
  }
 }

 public static void main(String args[]) {
  new Client("127.0.0.1", 5000);
 }
}

The Client sends a byte array to theServer. Server receives the byte array from the Client and sends the same byte array to the Client.
I have added comments in the code to explain the workflow more clearly.
I hope you have understood the concept. In case of any doubts, you are free to comment below.
Thanks for reading! Happy coding :)
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Location: India

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