Retomar o upload / download de arquivo após a conexão perdida (programação de soquete)
Estou escrevendo um programa para baixar / carregar um arquivo entre um cliente e um servidor usando a programação de soquete. O código que escrevi até agora funciona no sentido de que posso transferir arquivos com êxito. No entanto, se uma conexão falhar devido a um problema na rede / cliente / servidor enquanto um download / upload estiver ocorrendo .. eu preciso RETOMAR o download / upload a partir do ponto original (não deseja que os dados enviados originalmente sejam reenviados). Não tenho certeza de como fazer isso. Estou lendo o arquivo em uma matriz de bytes e enviando-o pela rede. Minha idéia inicial é que sempre que estiver baixando .. devo verificar se o arquivo já existe e ler os dados em uma matriz de bytes -> enviar os dados ao servidor para comparação e depois reter, urn os dados restantes do servidor comparando as matrizes de dois bytes. Mas isso parece ineficiente e tira o ponto de retomar um download (já que estou enviando os dados novamente). Nota: O nome do arquivo é um identificador exclusivo. Eu realmente apreciaria se alguém pudesse me dar sugestões sobre como eu deveria implementar a funcionalidade de retomar o arquivo?
Server side code:
package servers;
import java.io.*;
import java.net.*;
import java.util.Arrays;
public class tcpserver1 extends Thread
{
public static void main(String args[]) throws Exception
{
ServerSocket welcomeSocket = null;
try
{
welcomeSocket = new ServerSocket(5555);
while(true)
{
Socket socketConnection = welcomeSocket.accept();
System.out.println("Server passing off to thread");
tcprunnable tcprunthread = new tcprunnable(socketConnection);
Thread thrd = new Thread(tcprunthread);
thrd.start();
System.out.println(thrd.getName());
}
}
catch(IOException e){
welcomeSocket.close();
System.out.println("Could not connect...");
}
}
}
class tcprunnable implements Runnable
{
Socket socke;
public tcprunnable(Socket sc){
socke = sc;
}
public void download_server(String file_name)
{
System.out.println("Inside server download method");
try
{
System.out.println("Socket port:" + socke.getPort());
//System.out.println("Inside download method of thread:clientsentence is:"+clientSentence);
// Create & attach output stream to new socket
OutputStream outToClient = socke.getOutputStream();
// The file name needs to come from the client which will be put in here below
File myfile = new File("D:\\ "+file_name);
byte[] mybytearray = new byte[(int) myfile.length()];
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(myfile));
bis.read(mybytearray, 0, mybytearray.length);
outToClient.write(mybytearray, 0, mybytearray.length);
System.out.println("Arrays on server:"+Arrays.toString(mybytearray));
outToClient.flush();
bis.close();
}
catch(FileNotFoundException f){f.printStackTrace();}
catch(IOException ie){
ie.printStackTrace();
}
}
public void upload_server(String file_name){
try{
byte[] mybytearray = new byte[1024];
InputStream is = socke.getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
FileOutputStream fos = new FileOutputStream("D:\\ "+file_name);
BufferedOutputStream bos = new BufferedOutputStream(fos);
int bytesRead = is.read(mybytearray, 0, mybytearray.length);
bos.write(mybytearray, 0, bytesRead);
do {
baos.write(mybytearray);
bytesRead = is.read(mybytearray);
}
while (bytesRead != -1);
bos.write(baos.toByteArray());
System.out.println("Array on server while downloading:"+Arrays.toString(baos.toByteArray()));
bos.close();
}
catch(FileNotFoundException fe){fe.printStackTrace();}
catch(IOException ie){ie.printStackTrace();}
}
@Override
public void run()
{
try
{
System.out.println("Server1 up and running" + socke.getPort());
// Create & attach input stream to new socket
BufferedReader inFromClient = new BufferedReader
(new InputStreamReader(socke.getInputStream()));
// Read from socket
String clientSentence = inFromClient.readLine();
String file_name = inFromClient.readLine();
System.out.println("Sever side filename:" + file_name);
try{
if(clientSentence.equals("download"))
{
download_server(file_name);
}
else if(clientSentence.equals("upload"))
{
upload_server(file_name);
System.out.println("Sever side filename:" + file_name);
}
else
{
System.out.println("Invalid input");
}
}
catch(NullPointerException npe){
System.out.println("Invalid input!");
}
socke.close();
}
catch(IOException e)
{
e.printStackTrace();
System.out.println("Exception caught");
}
}
}
Código do lado do cliente:
package clients;
import java.io.*;
import java.net.*;
import java.util.Arrays;
public class tcpclient1
{
public static void main (String args[]) throws Exception
{
// Create input stream to send sentence to server
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
Socket clientSocket = null;
while(true){
System.out.println("Please enter the server you want to use");
System.out.println("Enter 1 for Server 1 and 2 for Server2");
String server_choice = inFromUser.readLine();
if(server_choice.equals("1")){
// Create client socket to connect to server
// The server to use will be specified by the user
clientSocket = new Socket("localhost",5555);
break;
}
else if(server_choice.equals("2"))
{
clientSocket = new Socket("localhost",5556);
break;
}
else
{
System.out.println("Invalid entry");
}
}
System.out.println("Please enter download for dowloading");
System.out.println("Please enter upload for uploading");
// sentence is what'll be received from input jsp
String sentence = inFromUser.readLine();
if(sentence.equals("download"))
{
download_client(clientSocket,sentence);
}
else if(sentence.equals("upload"))
{
upload_client(clientSocket,sentence);
}
else
{
System.out.println("Invalid input");
}
clientSocket.close();
}
public static void download_client(Socket clientSocket , String sentence)
{
try{
// Create output stream attached to socket
DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
// Send line to server
outToServer.writeBytes(sentence+'\n');
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the name of file to download:");
String file_to_download = inFromUser.readLine();
if(searching(file_to_download))
{
// Read local file and send that to the server for comparison
// DONT THINK THIS IS THE RIGHT WAY TO GO ABOUT THINGS SINCE IT BEATS THE PURPOSE OF RESUMING A DOWNLOAD/UPLOAD
}
// Send filetodownload to server
outToServer.writeBytes(file_to_download+'\n');
byte[] mybytearray = new byte[1024];
InputStream is = clientSocket.getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
FileOutputStream fos = new FileOutputStream("E:\\ "+file_to_download);
BufferedOutputStream bos = new BufferedOutputStream(fos);
int bytesRead = is.read(mybytearray, 0, mybytearray.length);
bos.write(mybytearray, 0, bytesRead);
do {
baos.write(mybytearray);
bytesRead = is.read(mybytearray);
}
while (bytesRead != -1);
bos.write(baos.toByteArray());
System.out.println("Array on client while downloading:"+Arrays.toString(baos.toByteArray()));
bos.close();
}
catch(FileNotFoundException fe){fe.printStackTrace();}
catch(IOException ie){ie.printStackTrace();}
}
public static void upload_client(Socket clientSocket, String sentence)
{
try{
// Create output stream attached to socket
DataOutputStream outToServer1 = new DataOutputStream(clientSocket.getOutputStream());
// Send line to server
outToServer1.writeBytes(sentence+'\n');
System.out.println("In the client upload method");
BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the name of file to upload:");
String file_to_upload = inFromUser.readLine();
//System.out.println("Cline side file name:"+file_to_upload);
outToServer1.writeBytes(file_to_upload+'\n');
System.out.println(file_to_upload);
OutputStream outtoserver = clientSocket.getOutputStream();
File myfile = new File("E:\\ "+file_to_upload);
byte[] mybytearray = new byte[(int) myfile.length()];
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(myfile));
bis.read(mybytearray, 0, mybytearray.length);
outtoserver.write(mybytearray, 0, mybytearray.length);
System.out.println("filename:"+file_to_upload+"Arrays on client while uploading:"+Arrays.toString(mybytearray));
outtoserver.flush();
bis.close();
}
catch(FileNotFoundException fe){fe.printStackTrace();}
catch(IOException ie){ie.printStackTrace();}
}
public static boolean searching(String file_name)
{
String file_path = "E:\\ "+file_name;
File f = new File(file_path);
if(f.exists() && !f.isDirectory()) { return true; }
else
return false;
}
}
O código acima funciona bem para transferir arquivos entre o cliente e o servidor.
Mais uma vez, realmente aprecio qualquer ajuda!