Need to make a \'simple\' ftp client/server coded in java, only problem is i kno

Question

Need to make a 'simple' ftp client/server coded in java, only problem is i know very little java and even less about socket programming so after failed attempts at trying to research how to do this, i ended up here. instructions quoted below.

"You are asked to develop a simple file transfer protocol. The protocol is based on client-server architecture. The client will connect to the server, sending user name and password for authentication (No encryption needed. Sending over plain TCP connection is fine). After passing authentication, the client will be able to download/upload files, list the files in the current directory at the server, and change the current directory to other directory at the server. After the client sends a request, the server should respond with some information to indicate if the request is processed or not. The server should also be able to serve another client after the current client logout.

You are required implement BOTH client and server sides. And your protocol should be able to transfer BOTH ASCII and binary files. You may refer to the FTP protocol for possible design options and typical commands. But no need to strictly follow or fully implement the FTP protocol. You can design your own protocol.

No GUI is required. A command line based UI is good enough.

ONLY use bare socket programming (NOT allow any other supportive libraries/packages such as HTTP or FTP classes)."

it is assumed that we only have one computer to run both the server and the client so the use of localhost instead of specific ip addresses is recommended.

thanks in advance to anyone who takes the time to answer this.

Explanation / Answer

we are sending the file with details as attributes of object of this class.

FileEvent.java:

import java.io.Serializable;

public class FileEvent implements Serializable {

public FileEvent() {
}

private static final long serialVersionUID = 1L;

private String destinationDirectory;
private String sourceDirectory;
private String filename;
private long fileSize;
private byte[] fileData;
private String status;

public String getDestinationDirectory() {
return destinationDirectory;
}

public void setDestinationDirectory(String destinationDirectory) {
this.destinationDirectory = destinationDirectory;
}

public String getSourceDirectory() {
return sourceDirectory;
}

public void setSourceDirectory(String sourceDirectory) {
this.sourceDirectory = sourceDirectory;
}

public String getFilename() {
return filename;
}

public void setFilename(String filename) {
this.filename = filename;
}

public long getFileSize() {
return fileSize;
}

public void setFileSize(long fileSize) {
this.fileSize = fileSize;
}

public String getStatus() {
return status;
}

public void setStatus(String status) {
this.status = status;
}

public byte[] getFileData() {
return fileData;
}

public void setFileData(byte[] fileData) {
this.fileData = fileData;
}
}

following server code, it simply creates a ServerSocket on port 4445 and waiting for incoming socket connections.Once a connection comes , it accepts the connection.And then it is reading the FileEvent object. Destination directory , file etc are creating. Data is writing to the output file too. Then closing and exiting.

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
private ServerSocket serverSocket = null;
private Socket socket = null;
private ObjectInputStream inputStream = null;
private FileEvent fileEvent;
private File dstFile = null;
private FileOutputStream fileOutputStream = null;

public Server() {

}

/**
* Accepts socket connection
*/
public void doConnect() {
try {
serverSocket = new ServerSocket(4445);
socket = serverSocket.accept();
inputStream = new ObjectInputStream(socket.getInputStream());
} catch (IOException e) {
e.printStackTrace();
}
}

/**
* Reading the FileEvent object and copying the file to disk.
*/
public void downloadFile() {
try {
fileEvent = (FileEvent) inputStream.readObject();
if (fileEvent.getStatus().equalsIgnoreCase("Error")) {
System.out.println("Error occurred ..So exiting");
System.exit(0);
}
String outputFile = fileEvent.getDestinationDirectory() + fileEvent.getFilename();
if (!new File(fileEvent.getDestinationDirectory()).exists()) {
new File(fileEvent.getDestinationDirectory()).mkdirs();
}
dstFile = new File(outputFile);
fileOutputStream = new FileOutputStream(dstFile);
fileOutputStream.write(fileEvent.getFileData());
fileOutputStream.flush();
fileOutputStream.close();
System.out.println("Output file : " + outputFile + " is successfully saved ");
Thread.sleep(3000);
System.exit(0);

} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
}

public static void main(String[] args) {
Server server = new Server();
server.doConnect();
server.downloadFile();
}
}

following client code it simply requests for a socket connection .After getting connection, it is creating the FileEvent object which contains the file details along with full content as byte stream.Then writing the FileEvent object to socket and exiting itself.

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

public class Client {
private Socket socket = null;
private ObjectOutputStream outputStream = null;
private boolean isConnected = false;
private String sourceFilePath = "E:/temp/songs/song1.mp3";
private FileEvent fileEvent = null;
private String destinationPath = "C:/tmp/downloads/";

public Client() {

}

/**
* Connect with server code running in local host or in any other host
*/
public void connect() {
while (!isConnected) {
try {
socket = new Socket("localHost", 4445);
outputStream = new ObjectOutputStream(socket.getOutputStream());
isConnected = true;
} catch (IOException e) {
e.printStackTrace();
}
}
}

/**
* Sending FileEvent object.
*/
public void sendFile() {
fileEvent = new FileEvent();
String fileName = sourceFilePath.substring(sourceFilePath.lastIndexOf("/") + 1, sourceFilePath.length());
String path = sourceFilePath.substring(0, sourceFilePath.lastIndexOf("/") + 1);
fileEvent.setDestinationDirectory(destinationPath);
fileEvent.setFilename(fileName);
fileEvent.setSourceDirectory(sourceFilePath);
File file = new File(sourceFilePath);
if (file.isFile()) {
try {
DataInputStream diStream = new DataInputStream(new FileInputStream(file));
long len = (int) file.length();
byte[] fileBytes = new byte[(int) len];
int read = 0;
int numRead = 0;
while (read < fileBytes.length && (numRead = diStream.read(fileBytes, read, fileBytes.length - read)) >= 0) {
read = read + numRead;
}
fileEvent.setFileSize(len);
fileEvent.setFileData(fileBytes);
fileEvent.setStatus("Success");
} catch (Exception e) {
e.printStackTrace();
fileEvent.setStatus("Error");
}
} else {
System.out.println("path specified is not pointing to a file");
fileEvent.setStatus("Error");
}
//Now writing the FileEvent object to socket
try {
outputStream.writeObject(fileEvent);
System.out.println("Done...Going to exit");
Thread.sleep(3000);
System.exit(0);
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}

}

public static void main(String[] args) {
Client client = new Client();
client.connect();
client.sendFile();
}
}

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