I have been trying to create a Messenger with file transfer capabilities, but I keep having too many null characters at the end. any time I use the file length to strip them, for some reason more of the file gets stripped and it just becomes a total mess. I'm not using any Java 7 or higher elements as I want it compatible with Java 6, and Windows 98 (grandma's PC).
I also get a lot of random null characters added into the file, im not sure how to avoid this
This is my code: Transmit
package com.androdome.lunacoffee.management;
import java.io.DataOutputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import com.androdome.lunacoffee.ErrorScreen;
import com.androdome.lunacoffee.SendScreen;
public class FileTransmitter implements Runnable{
String adds;
FileInputStream message;
int filecut = 4096;
byte[] fileName;
long fileSize;
SendScreen send;
public FileTransmitter(String address, FileInputStream msg, byte[] fnme, SendScreen snd, long l) {
adds = address;
send = snd;
message = msg;
fileName = fnme;
fileSize = l;
}
public void run()
{
try {
InetAddress add = InetAddress.getByName(adds);
Socket sock = new Socket(add, 11001);
DataOutputStream da = new DataOutputStream(sock.getOutputStream());
PrintWriter output = new PrintWriter(da);
da.write(fileName);
da.writeLong(message.getChannel().size());
byte[] filebuffer = new byte[filecut];
int g = 0;
int back = 0;
while((g = message.read(filebuffer)) != -1)
{
if(g != filecut && g > 0)
{
back = g;
}
da.write(filebuffer);
filebuffer = new byte[filecut];
}
da.writeInt(back);
System.out.print(back);
output.flush();
output.close();
send.incrementSent();
} catch (UnknownHostException e) {
send.incrementError();
// TODO Auto-generated catch block
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
e.printStackTrace(pw);
new ErrorScreen("Unable to send file", "Your file was not able to send because the host \"" + adds + "\" was not availible!", sw.toString());
pw.close();
try {
sw.close();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
} catch (IOException e) {
send.incrementError();
// TODO Auto-generated catch block
new ErrorScreen("Unable to send file", "Your file was not able to send due to a bad output stream!", e.getMessage());
}
}
}
Recieve:
package com.androdome.lunacoffee.management;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Arrays;
import com.androdome.lunacoffee.ErrorScreen;
import com.androdome.lunacoffee.FileScreen;
import com.androdome.lunacoffee.Main;
public class FileReciever implements Runnable {
int bufferSize = 4096;
int headerSize = 32;
byte[] filebuffer = new byte[bufferSize];
byte[] fileheader = new byte[headerSize];
Main main;
File downloadfile = new File("tmp");
File transferFile = new File("dnl.ldf");
public FileReciever(Main mn)
{
main = mn;
}
static byte[] trim(byte[] bytes)
{
int i = bytes.length - 1;
while (i >= 0 && bytes[i] == 0)
{
--i;
}
return Arrays.copyOf(bytes, i + 1);
}
public void run() {
try {
ServerSocket recieveSocket = new ServerSocket(11001);
while (this != null) {
try{
downloadfile.createNewFile();
Socket connectionSocket = recieveSocket.accept();
DataInputStream reader = new DataInputStream(connectionSocket.getInputStream());
reader.read(fileheader);
long fileSize = reader.readLong();
System.out.println(bufferSize);
filebuffer = new byte[bufferSize];
String fileName = new String(fileheader);
fileheader = new byte[headerSize];
FileOutputStream fw = new FileOutputStream(downloadfile);
while(reader.read(filebuffer) != -1)
{
fw.write(filebuffer);
filebuffer = new byte[bufferSize];
}
//reader.readInt();
reader.close();
fw.close();
//RandomAccessFile file = new RandomAccessFile(downloadfile, "Rwd");
//file.setLength(fileSize); // Strip off the last _byte_, not the last character
//file.close();
connectionSocket.close();
FileScreen fs = new FileScreen(downloadfile, fileName, connectionSocket.getInetAddress().getHostName());
fs.setVisible(true);
fs.setLocationRelativeTo(null);
}
catch(Exception ex)
{}
}
} catch (IOException e) {
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
e.printStackTrace(pw);
new ErrorScreen("Unable to start the File Recieve Thread", "Luna Messenger may already be running, or another program is using port 11001. Please close any program running on port 11001.", sw.toString());
pw.close();
try {
sw.close();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
}
}
In your above code,i think it makes following mistake. The first,you should add a number which indicate the filename's length.like this:
da.writeInt(fileName.length); //the added code
da.write(fileName);
On the FileReciever,the receive code is :
int fileNameLength = reader.readInt();
fileheader=new byte[fileNameLength];
read(reader,fileheader,0,fileNameLength);
the read method can read up to length bytes from input stream into a array of bytes until the stream is end.
public static int read(InputStream in, byte[] b, int off, int len) throws IOException {
if (len < 0) {
throw new IndexOutOfBoundsException("len is negative");
}
int total = 0;
while (total < len) {
int result = in.read(b, off + total, len - total);
if (result == -1) {
break;
}
total += result;
}
return total;
}
The second,it is not correctly that the FileTransmitter translate the file date to the FileReciever,and should not add a number at end.The appropriate approach is just writing file data to socket outputstream in FileTransmitter,and don't do any other things.Like this:
while((g = message.read(filebuffer)) != -1)
{
da.write(filebuffer,0,g);
}
On the orther hand,and how many bytes should be readed depend on the length of bytes that your readed from the socket's inputstream ago, when you read the bytes from socket oupustream into filebuffer.the receiver code:
int readLength;
int sumLength=0;
while((readLength=reader.read(filebuffer,0,(int)(fileSize-sumLength>filebuffer.length?filebuffer.length:fileSize-sumLength))) != -1){
sumLength+=readLength;
fw.write(filebuffer,0,readLength);
if(sumLength==fileSize){
break;
}
}