Re: java - problem on code to send file
- From: Sérgio Neves <mailpgrupos@xxxxxxxxxx>
- To: <programmingblind@xxxxxxxxxxxxx>
- Date: Fri, 18 Apr 2008 17:46:37 +0100
Hi,
Yes, it works well, thanks!
So, it's normal that the loop on the server side executes more times than the
loop on the client side, depending on the bytes that the server is able to read
(I thought the problem was on this, because I thought they had to execute the
same number of times).
I think you are saying is related to tcp congestion and these low-level things,
so I have forgotten this, although I have already had a network course.
But.. Is it a thing we have to know?
Imagine one person that has never had a network course and whishes to work with
sockets. On Sun's documentation, I don't find what you said (maybe I haven't
searched well, lol).
Thanks again
Best regards
Sérgio Neves
----- Original Message -----
From: public.niran
To: programmingblind@xxxxxxxxxxxxx
Sent: Friday, April 18, 2008 2:47 PM
Subject: Re: java - problem on code to send file
Although you are reading data on the server in pieces of 1024 bytes, it is
not necessary that each time there is 1024 bytes in the buffer to read. so the
read function can only read the available bytes which may be less than 1024
bytes.
so you should not asume that 1024 bytes has been read and write it to the
file, instead you should only write the number of bytes that are actualy
received.
Change
f.write(buf, 0, MAX);
to
f.write(buf, 0, RedBytes);
Also test the code with a text file rather than a zip. so that you can know
how much is getting send etc by just looking the output.
I am not a java programmer, so let me know if it solves your problem.
Niran
----- Original Message -----
From: Sérgio Neves
To: programmingblind@xxxxxxxxxxxxx
Sent: Friday, April 18, 2008 6:22 PM
Subject: java - problem on code to send file
Hi,
I need your help to solve this problem:
I've made a short application (one client and one server) which the unique
function is to send a file from the client to the server, but the file is not
sent correctly.
I send the file in pieces of 1024 bytes.
The server creates a socket to accept connections and after creates a
thread to handle the client, receiving the file size and after receives the
file content.
The client creates a socket to connect to the server, and after sends the
size of the file and then the file content.
Server and client finish their execution when the file is sent.
I've created two directories: c:\testclient (which owns the file to send to
the server) and c:\testserver (into which the file is copied) (I don't test if
the directories exist or things like that to not complicate the code).
What happens is that the loop which receives the file content (on the
server side) is executing more times than the loop on the client side (the
client loop always executes the correct number of iterations). I know this
because I've put a variable named "i" in both loops. And the stranger thing is
that the suplementary number of iterations on the server side is not always the
same. For example, in one execution it executes 3 more times, in another
execution it executes 4 more times.. I don't understand this.
Could anyone help with this, please? You can say if I wasn't clear enough.
The code follows
Best regards
Sérgio Neves
// client
import java.io.DataInputStream;
import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Inet4Address;
import java.net.Socket;
import java.net.UnknownHostException;
public class Client {
private static final int MAX = 1024;
static Socket s;
static ObjectInputStream ois;
static ObjectOutputStream oos;
public static void main (String[] args) throws UnknownHostException,
IOException, ClassNotFoundException {
try {
s = new Socket(Inet4Address.getByName("localhost"), 44444);
System.out.println("socket created");
ois = new ObjectInputStream(s.getInputStream());
oos = new ObjectOutputStream(s.getOutputStream());
System.out.println("get streams");
File file = new File("c:/testclient/eclipse-SDK-3.2.2-win32.zip");
long size = file.length();
oos.writeObject(size);
DataInputStream f = new DataInputStream(new FileInputStream(file));
long sentRemaining = size;
byte[] buf = new byte[MAX];
int i = 0;
do{
int writtenBytes;
if (sentRemaining < MAX){
writtenBytes = f.read(buf, 0, (int)sentRemaining);
oos.write(buf, 0, (int)sentRemaining);
oos.flush();
}else{
writtenBytes= f.read( buf, 0, MAX);
oos.write(buf, 0, MAX);
oos.flush();
}
sentRemaining -= writtenBytes;
i++;
}while(sentRemaining > 0);
System.out.println("terminated");
System.out.println("the loop executed " + i + " times");
} catch (EOFException eofException) {
System.out.println("end connection");
} catch (IOException ioException) {
System.out.println("error");
} finally {
ois.close();
oos.close();
s.close();
}
}
}
// server
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class Server implements Runnable {
private static final int MAX = 1024;
static ServerSocket s;
private Socket sb;
public static void main (String[] args) {
try{
s = new ServerSocket(44444);
//while (true) {
Socket sb;
sb = s.accept();
System.out.println("Connection accepted");
Server ser = new Server(sb);
new Thread(ser).start();
//}//close o while
}//close try
catch(IOException ex){
System.out.println();
}
}//close main
public void run () {
try{
ObjectOutputStream oos = new ObjectOutputStream(sb.getOutputStream());
ObjectInputStream ois = new ObjectInputStream(sb.getInputStream());
try{
DataOutputStream f = new DataOutputStream(new
FileOutputStream("c:/testserver/eclipse-SDK-3.2.2-win32.zip", true));
long receivedRemaining = (Long)ois.readObject();
byte[] buf = new byte[MAX];
int i = 0;
do{
int redBytes;
//System.out.println("itera");
if (receivedRemaining < MAX){
redBytes = (Integer)ois.read(buf, 0, (int)receivedRemaining);
f.write(buf, 0, (int)receivedRemaining);
//f.flush();
} else{
redBytes = (Integer)ois.read(buf, 0, MAX);
f.write(buf, 0, MAX);
//f.flush();
}
//System.out.println("red " + redBytes);
receivedRemaining -= redBytes;
//System.out.println("received remaining " + receivedRemaining);
i++;
}while(receivedRemaining > 0);
System.out.println("the loop executed " + i + " times");
f.close();
}catch(ClassNotFoundException ex){
} catch(IOException ex){
System.out.println("error");
} finally{
oos.close();
ois.close();
sb.close();
}
}
catch(IOException ex){
}
}
public Server (Socket sock) throws IOException{
sb = sock;
}
}
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