TCP Client Server communication using Java

//Client Side:

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package com.swain.cell;

import java.io.BufferedReader;

import java.io.DataOutputStream;

import java.io.FileOutputStream;

import java.io.InputStreamReader;

import java.net.Socket;

public class TCPClient {

       public static void main(String argv[]) throws Exception {

              String sentence;

              String modifiedSentence;

              BufferedReader inFromUser = new BufferedReader(new InputStreamReader(

                           System.in));

              Socket clientSocket = new Socket("localhost", 6780);

              // 6780 is the port used for TCP communication

              DataOutputStream outToServer = new DataOutputStream(

                           clientSocket.getOutputStream());

              BufferedReader inFromServer = new BufferedReader(new InputStreamReader(

                           clientSocket.getInputStream()));

              System.out.print(" file name : ");

              sentence = inFromUser.readLine();

              System.out.println("ffff --> " + sentence);

              outToServer.writeBytes(sentence + '\n');

              modifiedSentence = inFromServer.readLine();

              System.out.println("FROM SERVER: " + modifiedSentence);

              FileOutputStream f = new FileOutputStream("copy of " + sentence);

              DataOutputStream d = new DataOutputStream(f);

              byte fd[] = new byte[1024];

              fd = modifiedSentence.getBytes();

              d.write(fd);

              clientSocket.close();

       }

}

//Server Side:

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package com.swain.cell;

import java.io.BufferedReader;

import java.io.DataOutputStream;

import java.io.FileReader;

import java.io.InputStreamReader;

import java.net.ServerSocket;

import java.net.Socket;

public class TCPServer {

       public static void main(String argv[]) throws Exception {

              String clientSentence;

              String capitalizedSentence;

              ServerSocket welcomeSocket = new ServerSocket(6780);

              while (true) {

                     Socket connectionSocket = welcomeSocket.accept();

                     BufferedReader inFromClient =

                     new BufferedReader(new InputStreamReader(

                                  connectionSocket.getInputStream()));

                     DataOutputStream outToClient = new DataOutputStream(

                                  connectionSocket.getOutputStream());

                     clientSentence = inFromClient.readLine();

                     System.out.println("Received: " + clientSentence);

                     BufferedReader br = new BufferedReader(new FileReader(

                                  clientSentence));

                     String filecontent = "";

                     // File content is cleared

                     filecontent = br.readLine();

                     System.out.println("file : " + filecontent);

                     outToClient.writeBytes(filecontent + '\n');

              }

       }

}