Develop Reference

Java Socket Programming Buffer for Large File

I am trying to transfer a large file from a server to a client. My code so far works but only if I set the buffer size in the client code to the exact size of the file. I won't always know what the file size is going to be. I keep finding examples that claim it doesn't matter what the size of the file or buffer is because it will just keep reading from the input stream...? However, when I implement the code that supposedly does this, it transfers 0 bytes.
Client:
public static void main (String [] args ) throws IOException {
int bytesRead;
int current = 0;
FileOutputStream fos = null;
BufferedOutputStream bos = null;
Socket sock = null;
try {
sock = new Socket(hostname, 20000);
System.out.println("Connecting...");
// receive file
InputStream is = sock.getInputStream();
fos = new FileOutputStream(FILE_TO_RECEIVE);
bos = new BufferedOutputStream(fos);
//////////// replaced this ////////////////////////////
byte[] buffer = new byte[BUFFER_SIZE];
bytesRead = is.read(buffer,0,buffer.length);
current = bytesRead;
do {
bytesRead = is.read(buffer, current, (buffer.length-current));
if(bytesRead >= 0){ current += bytesRead;}
} while(bytesRead > 0);
bos.write(buffer, 0 , current);
///////////////////////////////////////
// with this:
// int count;
// byte[] buffer = new byte[8192];
// while ((count = is.read(buffer)) > 0)
// {
// bos.write(buffer, 0, count);
// }
//////////// transfers 0 bytes ///////////
bos.flush();
System.out.println("File " + FILE_TO_RECEIVE
+ " downloaded (" + current + " bytes read)");
}
finally {
if (fos != null){ fos.close();}
if (bos != null){ bos.close();}
if (sock != null){ sock.close();}
}
}
Server:
public static void main(String[] args) throws IOException{
FileInputStream fis = null;
BufferedInputStream bis = null;
OutputStream os = null;
ServerSocket servsock = null;
Socket sock = null;
try {
servsock = new ServerSocket(20000);
while (true) {
System.out.println("Waiting...");
try {
sock = servsock.accept();
System.out.println("Accepted connection : " + sock);
// send file
File myFile = new File (FILE_TO_SEND);
byte [] mybytearray = new byte [(int)myFile.length()];
fis = new FileInputStream(myFile);
bis = new BufferedInputStream(fis);
bis.read(mybytearray,0,mybytearray.length);
os = sock.getOutputStream();
System.out.println("Sending " + FILE_TO_SEND + "(" + mybytearray.length + " bytes)");
os.write(mybytearray,0,mybytearray.length);
os.flush();
System.out.println("Done.");
}
finally {
if (bis != null){ bis.close();}
if (os != null){ os.close();}
if (sock!=null){ sock.close();}
}
}
}
finally {
if (servsock != null){
servsock.close();
}
}
}
Thank you for your help

Your copy loops are both different, and both nonsense. One of them isn't even a loop. Try this:
while ((count = in.read(buffer)) > 0)
{
out.write(buffer, 0, count);
}
This works for any buffer of size >= one byte.
Use this at both ends.

I want to download all files from PC's folder from my android for this m doing java sockets but achieved 1st file correctly others are garbage

*i have have a folder in my pc in c:/ name share and in that i have 4 pictures after running my client and server code i got all 4 picture downloaded in my android emulator but only first image is correctly download other 3 are garbage
here is my code
SERVER SIDE
public class Multiplefilessending
{
public static void main(String[] args) throws IOException,EOFException
{
FileOutputStream fos;
BufferedOutputStream bos;
OutputStream output;
int len;
int smblen;
InputStream in;
boolean flag=true;
DataInputStream clientData;
BufferedInputStream clientBuff;
System.out.println("Waiting for Connection");
ServerSocket serverSocket = new ServerSocket(5991);
Socket clientSocket = null;
clientSocket = serverSocket.accept();
////////////////////////
File myFile = new File("C:/share");
File[] Files = myFile.listFiles();
OutputStream os = clientSocket.getOutputStream();
DataOutputStream dos = new DataOutputStream(os);
dos.writeInt(Files.length);
for (int count=0;count<Files.length;count ++)
{
dos.writeUTF(Files[count].getName());
}
for (int count=0;count<Files.length;count ++)
{
int filesize = (int) Files[count].length();
dos.writeInt(filesize);
}
for (int count=0;count<Files.length;count ++)
{
int filesize = (int) Files[count].length();
byte [] buffer = new byte [filesize];
//FileInputStream fis = new FileInputStream(myFile);
FileInputStream fis = new FileInputStream(Files[count].toString());
BufferedInputStream bis = new BufferedInputStream(fis);
//Sending file name and file size to the server
bis.read(buffer, 0, buffer.length); //This line is important
dos.write(buffer, 0, buffer.length);
dos.flush();
//dos.close();
}
if (flag==false){
clientSocket = serverSocket.accept();
flag = true;
}
//Closing socket
//dos.close();
clientSocket.close();
}
}
And
CLIENT SIDE
Socket sock = new Socket("10.0.2.2", 5991);
System.out.println("Connecting.........");
FileOutputStream fos;
BufferedOutputStream bos;
OutputStream output;
DataOutputStream dos;
int len;
int smblen;
InputStream in;
boolean flag=true;
DataInputStream clientData;
BufferedInputStream clientBuff;
while (true)
{
//while(true && flag==true){
while(flag==true)
{
in = sock.getInputStream(); //used
clientData = new DataInputStream(in); //use
clientBuff = new BufferedInputStream(in); //use
int fileSize = clientData.read();
ArrayList<File>files=new ArrayList<File>(fileSize); ArrayList<Integer>sizes = new ArrayList<Integer>(fileSize); //store file size from client
//Start to accept those filename from server
for (int count=0;count < fileSize;count ++){
File ff=new File(clientData.readUTF());
files.add(ff);
}
for (int count=0;count < fileSize;count ++){
sizes.add(clientData.readInt());
}
for (int count =0;count < fileSize ;count ++)
{
if (fileSize - count == 1)
{
flag =false;
}
len=sizes.get(count);
//System.out.println("File Size ="+len);
output = new FileOutputStream("/mnt/sdcard/" + files.get(count));
dos=new DataOutputStream(output);
bos=new BufferedOutputStream(output);
byte[] buffer = new byte[1024];
bos.write(buffer, 0, buffer.length); //This line is important
while (len > 0 && (smblen = clientData.read(buffer)) > 0)
{
dos.write(buffer, 0, smblen);
len = len - smblen;
dos.flush();
}
dos.close(); //It should close to avoid continue deploy by resource under view
}
}
if (flag==false)
{
sock = new Socket("10.0.2.2", 5991);
flag = true;
}
} }
catch (UnknownHostException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}

Your read loop is incorrect. You need to constrain the read length so you don't over-run into the next file:
while (len > 0 && (smblen = clientData,read(buffer, 0, len > buffer.length ? buffer.length : (int)len)) > 0)
{
bos.write(buffer, 0, smblen);
len -= smblen;
}
Other comments:
File lengths are longs, not ints.
Use a bigger buffer, at least 8192, and declare it once at the top of the method. You don't need a new one per file.
Don't flush inside the loop.
Don't keep recreating the streams. Use the same ones for the life of the socket, at both ends.
You should be writing to 'bos', not 'dos'. In fact you don't need the DataOutputStream to write to the file at all. Just the BufferedOutputStream and the FileOutputStream.
You should send one filename, one length, then one file, then the next filename, ... That way the sender can stop any time. That gets rid of the initial count, and it also gets rid of all that 'flag' nonsense. If you get EOFException reading the next name, the peer has closed the connection.

File download from PC to Android device - OutputStream write( ) stucks for large files

I'm trying to download a file from PC to Android device (emulator or physical)
Everything goes fine for small and medium sized files, but when I try to send something larger than say 10Mb, server never reaches this statement out2.println("ready");, hence the client hangs waiting for "ready" from server
Seems that server stucks at this: os.write(bytearray, 0, bytearray.length);
So far I've tried this on emulator, I'm going to report about results on a real device shortly
Here is my client part, in Android app: Android client sends "download" string to server, then receives "ready" reply from it, and starts reading file from InputStream
int filesize = 2022386;
int bytesRead;
int currentTot = 0;
Socket socket1 = new Socket("172.16.6.119", 50001); //data line
Socket socket2 = new Socket("172.16.6.119", 50001); //control line
BufferedReader in2 = new BufferedReader(new InputStreamReader(socket2.getInputStream()));
PrintWriter out2 = new PrintWriter(socket2.getOutputStream(), true);
out2.println("download:"); //control line
String usrtxt = in2.readLine();
if(usrtxt.substring(0,5).equals("ready")) //control line
{
byte [] bytearray = new byte [filesize];
InputStream is = socket1.getInputStream(); //data line
FileOutputStream fos = new FileOutputStream(Environment.getExternalStorageDirectory().toString() + "/sunset.jpg");
BufferedOutputStream bos = new BufferedOutputStream(fos);
bytesRead = is.read(bytearray,0,bytearray.length);
currentTot = bytesRead;
Log.e("DOWNLOAD", "init value: bytesread = " + Integer.toString(bytesRead));
do {
bytesRead =
is.read(bytearray, currentTot, (bytearray.length-currentTot)); //<--does not pull data (WHY?)
Log.e("DOWNLOAD", "bytesread = " + Integer.toString(bytesRead));
if(bytesRead >= 0) currentTot += bytesRead;
} while(bytesRead > -1);
out1.println("finished:");
bos.write(bytearray, 0 , currentTot);
Log.e("DOWNLOAD", Integer.toString(currentTot));
bos.flush();
bos.close();
socket1.close(); socket2.close();
}
And this is my server code: it accepts connection from client, then receives "download" string from it, replies with "ready", and puts the file onto OutputStream
while (true) {
final Socket socket = serverSocket.accept(); //data line
final Socket socket2= serverSocket.accept(); //control line
BufferedReader in2 = new BufferedReader(new InputStreamReader(socket2.getInputStream()));
PrintWriter out2 = new PrintWriter(socket2.getOutputStream(), true);
String usrtxt = in2.readLine(); //control line
if(usrtxt.substring(0,8).equals("download"))
{
System.out.println("accepted download request. sending file");
File transferFile = new File("sunset.jpg");
byte[] bytearray = new byte[(int)transferFile.length()];
FileInputStream fin = new FileInputStream(transferFile);
BufferedInputStream bin = new BufferedInputStream(fin);
bin.read(bytearray, 0, bytearray.length);
OutputStream os = socket.getOutputStream();
os.write(bytearray, 0, bytearray.length); //data line
os.flush();
os.close();
out2.println("ready"); //control line
socket.close(); socket2.close();
bin.close(); fin.close();
System.out.println("file transfer complete");
}//end if
}//end while

This is no way to copy streams. It assumes too many things that may not be true.
The canonical way in Java is as follows:
byte[] buffer = new byte[8192]; // or whatever you like, anything above zero. Note that it doesn't have to be the size of the file
int count;
while ((count = in.read(buffer)) > 0)
{
out.write(buffer, 0, count);
}
If you know the length in advance and you want to keep the socket open afterwards, keep track of the bytes transferred so far via 'total += count;' after the read call inside the loop, and change the read call to read(buffer, 0, length-total > buffer.length ? buffer.length : (int)(length-total)).

java send file using sockets

I am trying to send a file from one computer to another using Java. I have written the code below, it works fine if both sender and receiver are started in the same computer but if they work on different machines received file size is bigger than the original file and it is corrupted.
Note: I am trying to transfer files which are max 10 MBs.
How can I fix this?
Sender:
ServerSocket server_socket = new ServerSocket(8989);
File myFile = new File(myPath);
Socket socket = server_socket.accept();
int count;
byte[] buffer = new byte[1024];
OutputStream out = socket.getOutputStream();
BufferedInputStream in = new BufferedInputStream(new FileInputStream(myFile));
while ((count = in.read(buffer)) > 0) {
out.write(buffer, 0, count);
out.flush();
}
socket.close();
Receiver:
Socket socket = new Socket(address, 8989);
FileOutputStream fos = new FileOutputStream(anotherPath);
BufferedOutputStream out = new BufferedOutputStream(fos);
byte[] buffer = new byte[1024];
int count;
InputStream in = socket.getInputStream();
while((count=in.read(buffer)) >0){
fos.write(buffer);
}
fos.close();
socket.close();

On the client side you write up to count bytes and send them:
while ((count = in.read(buffer)) > 0) {
out.write(buffer, 0, count);
on the server side you read up to count bytes - but then you write the whole buffer to file!
while((count=in.read(buffer)) > 0){
fos.write(buffer);
Just change it to:
fos.write(buffer, 0, count);
and you'll be on the safe side. BTW your program has another small bug: read() can return 0 which doesn't mean InputStream ended. Use >= instead:
count = in.read(buffer)) >= 0
Have you considered IOUtils.copy(InputStream, OutputStream) from Apache Commons? It would reduce your whole while loops to:
OutputStream out = socket.getOutputStream();
InputStream in = new FileInputStream(myFile);
IOUtils.copy(in, out);
socket.close();
Less code to write, less code to test. And buffering is done internally.

Remember that in.read(buffer) not necessarily fills up the whole buffer with new data. Therefore you should make sure you don't write the whole buffer. Change
while((count=in.read(buffer)) >0){
fos.write(buffer);
}
to
while((count=in.read(buffer)) >0){
fos.write(buffer, 0, count);
}

sender
Socket sock = new Socket("127.0.0.1", 5991);
System.out.println("Connecting.........");
File myFile = new File("/root/qrcode/");
File[] files = myFile.listFiles();
OutputStream os = sock.getOutputStream();
BufferedOutputStream bos = new BufferedOutputStream(os);
DataOutputStream dos = new DataOutputStream(bos);
dos.writeInt(files.length);
long totalBytesRead = 0;
int percentCompleted = 0;
for(File file : files)
{
long length = file.length();
dos.writeLong(length);
String name = file.getName();
dos.writeUTF(name);
FileInputStream fis = new FileInputStream(file);
BufferedInputStream bis = new BufferedInputStream(fis);
int theByte = 0;
while((theByte = bis.read()) != -1)
{
totalBytesRead += theByte;
bos.write(theByte);
}
// System.out.println("file read");
bis.close();
}
dos.close();
//Closing socket
sock.close();
receiver
ServerSocket serverSocket = new ServerSocket(5991);
while(true) {
Socket clientSocket = null;
System.out.println("Starting...");
clientSocket = serverSocket.accept();
InputStream in = clientSocket.getInputStream(); //used
BufferedInputStream bis = new BufferedInputStream(in);
String dirPath ;
dirPath = "/root/NewFolder";
try{
DataInputStream dis = new DataInputStream(bis);
int filesCount = dis.readInt();
File[] files = new File[filesCount];
long f_l = 0;
int count =0 ;
long totalBytesRead = 0;
int percentCompleted = 0;
for(int i = 0; i < filesCount; i++)
{
long fileLength = dis.readLong();
String fileName = dis.readUTF();
f_l = f_l +fileLength;
files[i] = new File(dirPath + "/" + fileName);
FileOutputStream fos = new FileOutputStream(files[i]);
BufferedOutputStream bos = new BufferedOutputStream(fos);
int tot = 0;
for(int j = 0; j < fileLength; j++) {
bos.write(bis.read());
}
bos.close();
}
}catch(Exception ex)
{
System.out.println("error in socket programming ");
}
}

problem with server and client , working on my machine not working on another

hello guys i have designed a server client which transfers data through sockets. Everything is ok when i run it on my machine it works 100% of the time. When i run the server on another machine and the client on mine, i am unable to get data. when i run the server on my machine and the client on theirs i am unable to put data , but i can get. i dont know what is going on, maybe you can shed some light.
There is more code that makes this work correctly but i omit that out to reduce the complications . Please if you get a chanse look at this and tell me why it works on my system but not on the server? and does anyone know how to debug this? i mean this is run on the server how can i debug a server since i cannot be there (and everything works correctly on my system?)
Server :
if (get.equals("get")) {
try {
Copy copy = new Copy(socket, dir);//maybe dir is not needed
String name = input.substring(4);
File checkFile = new File(dir.getCurrentPath(), name);
DataOutputStream outToClient = new DataOutputStream(socket.getOutputStream());
if (checkFile.isFile() && checkFile.exists()) {
outToClient.writeBytes("continue" + "\n");
BufferedReader inFromServer = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
boolean cont = false;
String x;
while (!cont) {
if ((x = inFromServer.readLine()).equals("continue")) {
cont = true;
}
}
copy.copyFile(name);
output = "File copied to client successfully" + "\n";
} else {
outToClient.writeBytes("File failed to be copied to client" + "\n");
output = "";
}
} catch (Exception e) {
output = "Failed to Copy File to client" + "\n";
}
} else if (get.equals("put")) {
//so the client sends: the put request
//then sends the length
try {
DataInputStream inFromClient = new DataInputStream(socket.getInputStream());
DataOutputStream outToClient = new DataOutputStream(socket.getOutputStream());
outToClient.writeBytes("continue" + "\n");
long lengthLong = (inFromClient.readLong());
int length = (int) lengthLong;
byte[] recieveFile = new byte[length];//FIX THE LENGTH
// InputStream is = socket.getInputStream();
FileOutputStream fos = new FileOutputStream("Copy " + input.substring(4));
BufferedOutputStream bos = new BufferedOutputStream(fos);
int bytesRead;
int current = 0;
bytesRead = inFromClient.read(recieveFile, 0, recieveFile.length);
current = bytesRead;
do {
bytesRead = inFromClient.read(recieveFile, current, (recieveFile.length - current));
if (bytesRead >= 0)
current += bytesRead;
} while (bytesRead > 0); // FIX THE LENGTH
bos.write(recieveFile, 0, current);
bos.flush();
bos.close();
output = "File copied to Server successfully" + " \n";
The copy class:
File checkFile = new File(dir.getCurrentPath(), file);
if (checkFile.isFile() && checkFile.exists()) {
DataOutputStream outToClient = new DataOutputStream(socket.getOutputStream());
// byte[] receivedData = new byte[8192];
File inputFile = new File(dir.getCurrentPath(), file);
byte[] receivedData = new byte[(int) inputFile.length()];
long length = inputFile.length();
outToClient.writeLong(length);
//maybe wait here for get request?
DataInputStream dis = new DataInputStream(new FileInputStream(getCopyPath(file)));
dis.read(receivedData, 0, receivedData.length);
OutputStream os = socket.getOutputStream();
outToClient.write(receivedData, 0, receivedData.length);//outputStreasm replaced by Datatoutputstream
outToClient.flush();
The client class:
else if (sentence.length() > 3 && sentence.substring(0, 3).equals("get")) {
outToServer.writeBytes(sentence + "\n");
String response = inFromServer.readLine();
if (response.equals("File failed to be copied to client")) {
System.out.println(response);
} else {
DataInputStream inFromClient = new DataInputStream(clientSocket.getInputStream());
DataOutputStream outToClient = new DataOutputStream(clientSocket.getOutputStream());
outToClient.writeBytes("continue" + "\n");
long lengthLong = (inFromClient.readLong());
int length = (int) lengthLong;
byte[] recieveFile = new byte[length];
FileOutputStream fos = new FileOutputStream("Copy " + sentence.substring(4));
BufferedOutputStream bos = new BufferedOutputStream(fos);
int bytesRead;
int current = 0;
bytesRead = inFromClient.read(recieveFile, 0, recieveFile.length);
current = bytesRead;
do {
bytesRead = inFromClient.read(recieveFile, current, (recieveFile.length - current));
if (bytesRead >= 0)
current += bytesRead;
} while (bytesRead > 0);
bos.write(recieveFile, 0, current);
bos.flush();
bos.close();
}
} else if (sentence.length() > 3 && sentence.substring(0, 3).equals("put")) {
File checkFile = new File(dir.getCurrentPath(), sentence.substring(4));
if (checkFile.isFile() && checkFile.exists()) {
try {
outToServer.writeBytes(sentence + "\n");
boolean cont = false;
String x;
while (!cont) {
if ((x = inFromServer.readLine()).equals("continue")) {
cont = true;
}
}
String name = sentence.substring(4);
copy.copyFile(name);