Develop Reference

Java request file, send file (Client-server)

I'm making a Client-Server. I've gotten as far as that the server can send a hardcoded file, but not a client specified. I will have to send only text files. As far as I have understood: the clients firstly sends the file name and then, the server sends it, nothing complicated, but I'm getting all kinds of errors, this code is getting a connection reset/socket closed error. The main problem is, that hadn't got much time to research networking.
Ill appreciate any help I can get.
EDIT.
I found a work around, closing a stream causes the socket to close, why is that? It shouldn't happen, should it?
Server Side:
InputStream sin=newCon.getInputStream();
DataInputStream sdata=new DataInputStream(sin);
location=sdata.readUTF();
//sdata.close();
//sin.close();
File toSend=new File(location);
byte[] array=new byte[(int)toSend.length()];
FileInputStream fromFile=new FileInputStream(toSend);
BufferedInputStream toBuffer=new BufferedInputStream(fromFile);
toBuffer.read(array,0,array.length);
OutputStream out=newCon.getOutputStream(); //Socket-closed...
out.write(array,0,array.length);
out.flush();
toBuffer.close();
newCon.close();
ClientSide:
int bytesRead;
server=new Socket(host,port);
OutputStream sout=server.getOutputStream();
DataOutputStream sdata=new DataOutputStream(sout);
sdata.writeUTF(interestFile);
//sdata.close();
//sout.close();
InputStream in=server.getInputStream(); //socket closed..
OutputStream out=new FileOutputStream("data.txt");
byte[] buffer=new byte[1024];
while((bytesRead=in.read(buffer))!=-1)
{
out.write(buffer,0,bytesRead);
}
out.close();
server.close();

Try reading the file in chunks from Server while writing to client output stream rather than creating a temp byte array and reading entire file into memory. What if requested file is large? Also close the new Socket on server-side in a finally block so socket is closed even if an exception is thrown.
Server Side:
Socket newCon = ss.accept();
FileInputStream is = null;
OutputStream out = null;
try {
InputStream sin = newCon.getInputStream();
DataInputStream sdata = new DataInputStream(sin);
String location = sdata.readUTF();
System.out.println("location=" + location);
File toSend = new File(location);
// TODO: validate file is safe to access here
if (!toSend.exists()) {
System.out.println("File does not exist");
return;
}
is = new FileInputStream(toSend);
out = newCon.getOutputStream();
int bytesRead;
byte[] buffer = new byte[4096];
while ((bytesRead = is.read(buffer)) != -1) {
out.write(buffer, 0, bytesRead);
}
out.flush();
} finally {
if (out != null)
try {
out.close();
} catch(IOException e) {
}
if (is != null)
try {
is.close();
} catch(IOException e) {
}
newCon.close();
}
If you use Apache Common IOUtils library then you can reduce much of the code to read/write files to streams. Here 5-lines down to one line.
org.apache.commons.io.IOUtils.copy(is, out);
Note that having a server that serves files by absolute path to remote clients is potentially dangerous and the target file should be restricted to a given directory and/or set of file types. Don't want to serve out system-level files to unauthenticated clients.

Weird stuff while viewing a file which was transferred with sockets in java

Well i am trying to transfer a file using sockets in java
Here is the code
Client Code
try{
// get streams
DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
DataInputStream din = new DataInputStream (socket.getInputStream());
dos.writeUTF(fileName);
dos.flush();
boolean isOk = din.readBoolean();
if(!isOk){
throw new StocFileNotFound("Fisierul: " + fileName +" was not found on:" + address.toString());
} else {
baos = new ByteArrayOutputStream();
byte biti [] = new byte[1024];
while(din.read(biti,0,1024) != -1){
baos.write(biti,0,biti.length);
}
}
}
catch(IOException e){}
finally {
try{ socket.close(); } catch (IOException e){}
}
and then I return the baos.toByteArray() and write it to a file with the OutputStream`s write method.
Server code
try{
DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
DataInputStream din = new DataInputStream (socket.getInputStream());
// check if it is really a file or if it is an existing file
File file = new File(din.readUTF());
// write false
if ( !file.exists() || !file.isFile() ){
dos.writeBoolean(false);
dos.flush();
}
// write true and write the file
else {
byte biti[] = new byte[1024];
dos.writeBoolean(true);
FileInputStream fis = new FileInputStream(file);
while(fis.read(biti,0,1024) != -1){
dos.write(biti,0,biti.length);
}
dos.flush();
try{ fis.close(); } catch (IOException e){}
}
} catch (IOException e){}
finally {
try{socket.close();}catch(IOException e){}
}
The problem
When i transfer a .txt file and view it in gedit it shows the text followed by multiple \00\00\00, though when i open it using notepad(in wine) it shows only the text. Plus viewing images and .doc works also. So is it something with gedit or is it with my program?
Edit
i was sending something like "hi, hope it works!"

This is the problem (or at least a problem):
while(fis.read(biti,0,1024) != -1)
{
dos.write(biti,0,biti.length);
}
You're always writing out the whole buffer, however many bytes were actually read. You should have:
int bytesRead;
while ((bytesRead = fis.read(biti, 0, 1024)) != -1)
{
dos.write(biti, 0, bytesRead);
}
(You've got the same problem in both bits of code.)
You might want to look at Guava which has various utility methods to relieve you of a lot of the tedium (and possible error) of writing this kind of code over and over again.

The read method will return the actual number of bytes read from the stream. You should use that as a parameter to your write method, or else you will be writing garbage to it.

Sending file from one client to another client using socket in java

Hello everyone ,
I am trying to develop the application for transfering/sending the file like SKYPE works.So I am using socket for transfering file from one computer(client) to another computer(client) .I am able to transfer file from one client to server using this. code.But when I try to send the same file from server to second client.It is transfering with 0 byte also give socket close exception so I try to create new socket object at client side.So Now the Exception not coming but file not transfering to client.After debugging I found that the file is successfully sent to client by server but at client side socket is not able to read the data and waiting for data.I can’t find any better solution.If anyone knows anything about this Please tell me.If you have any other solution for file transfer than also tell me.Thanks in advance
Below is my code
Server code:
public class ChatServer
{
serversocket = new ServerSocket(1436);
thread = new Thread(this);
thread.start();
/*************Thread Implementation***************/
public void run()
{
/*********Accepting all the client connections and create a seperate thread******/
while(thread != null)
{
try
{
/********Accepting the Server Connections***********/
socket = serversocket.accept();
/******* Create a Seperate Thread for that each client**************/
chatcommunication = new ChatCommunication(this,socket);
thread.sleep(THREAD_SLEEP_TIME);
}
catch(InterruptedException _INExc) { ExitServer(); }
catch(IOException _IOExc) { ExitServer(); }
}
}
protected void SendGroupFile(Socket ClientSocket, String FileName,String GroupName,String UserName) throws IOException
{
try
{
// receive file from Client
byte [] mybytearray = new byte [filesize];
InputStream is = socket.getInputStream();
FileOutputStream fos = new FileOutputStream(Filepath);
BufferedOutputStream bos = new BufferedOutputStream(fos);
int bytesRead = is.read(mybytearray,0,mybytearray.length);
current = bytesRead;
do {
bytesRead =is.read(mybytearray, current, (mybytearray.length-current));
System.out.println("Reading Bytes server"+bytesRead);
if(bytesRead >= 0)
current += bytesRead;
} while(bytesRead > -1);
bos.write(mybytearray,0,current);
bos.flush();
bos.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/***** Function To Send a File to Client **********/
protected void SendGroupFileClient(Socket ClientSocket, String FileName,String GroupName,String UserName)
{
try {
int m_userListSize = userarraylist.size();
clientobject = GetClientObject(GroupName);
if(clientobject != null)
for(G_ILoop = 0; G_ILoop < m_userListSize; G_ILoop++)
{
clientobject = (ClientObject) userarraylist.get(G_ILoop);
if((clientobject.getGroupName().equals(GroupName)) && (!(clientobject.getUserName().equals(UserName))))
{
{
File myFile = new File (Filepath);
byte [] mybytearray = new byte [(int)myFile.length()];
FileInputStream fis = new FileInputStream(myFile);
BufferedInputStream bis = new BufferedInputStream(fis);
bis.read(mybytearray,0,mybytearray.length);
os = socket.getOutputStream();
System.out.println("Sending...");
os.write(mybytearray,0,mybytearray.length);
os.flush();
os.close();
}
}catch(IOException _IOExc)
{
_IOExc.printStackTrace();
}
}
}
ChatCommunication .java
public class ChatCommunication implements Runnable,CommonSettings
{
Thread thread;
Socket socket;
DataInputStream inputstream;
String RFC;
ChatServer Parent;
/********Initialize the Socket to the Client***********/
ChatCommunication(ChatServer chatserver,Socket clientsocket)
{
Parent = chatserver;
socket = clientsocket;
try
{
inputstream = new DataInputStream(new BufferedInputStream(socket.getInputStream()));
}catch(IOException _IOExc) { }
thread = new Thread(this);
thread.start();
}
public void run()
{
while(thread != null)
{
try {
RFC = inputstream.readLine();
if(RFC.startsWith("FILEGRUP"))
{
Parent.SendGroupFile(socket,RFC.substring(9,RFC.indexOf("!")),RFC.substring(RFC.indexOf("!")+1,RFC.indexOf("*")),RFC.substring(RFC.indexOf("*")+1));
}
if(RFC.startsWith("FILEGET"))
{
Parent.SendGroupFileClient(socket,RFC.substring(8,RFC.indexOf("!")),RFC.substring(RFC.indexOf("!")+1,RFC.indexOf("*")),RFC.substring(RFC.indexOf("*")+1));
}
}catch(Exception _Exc)
{
Parent.RemoveUserWhenException(socket);QuitConnection();
}
}
}
Client code
class Client extends JFrame
{
ServerName="192.168.1.103";
ServerPort=1436;
Client()
{
socket = new Socket(ServerName,ServerPort);
SendGroupFileToServer(Filepath,SelectedGroup);
}
/*******Function To Send File To Server and receiving the file ***********/
protected void SendGroupFileToServer(String FileName, String ToGroup)
{
try {
dataoutputstream.writeBytes(FileName.concat("!").concat(ToUser)+"\r\n");
//send file to sever
File myFile = new File (FileName.substring(9));
byte [] mybytearray = new byte [(int)myFile.length()];
FileInputStream fis = new FileInputStream(myFile);
BufferedInputStream bis = new BufferedInputStream(fis);
bis.read(mybytearray,0,mybytearray.length);
OutputStream os = socket.getOutputStream();
System.out.println("Sending...");
os.write(mybytearray,0,mybytearray.length);
os.flush();
os.close();
System.out.println("File successfully Sended to server");
}catch(IOException _IoExc) { QuitConnection(QUIT_TYPE_DEFAULT);}
try {
socket1 = new Socket(ServerName,ServerPort); //Creating new Socket
dataoutputstream = new DataOutputStream(socket1.getOutputStream());
dataoutputstream.writeBytes("FILEGET"+FileName.concat("!").concat(ToGroup+"*"+UserName)+"\r\n"); //sending string to server
} catch (IOException e1) {
e1.printStackTrace();
}
// receive file sended by server
byte [] mybytearray = new byte [filesize];
InputStream is;
try {
is = socket1.getInputStream();
FileOutputStream fos = new FileOutputStream(Filepath);
BufferedOutputStream bos = new BufferedOutputStream(fos);
int bytesRead = is.read(mybytearray,0,mybytearray.length);
current = bytesRead; //up to this working fine
do {
bytesRead =is.read(mybytearray, current, (mybytearray.length-current)); //not reading the file data sent by server just waiting and not go ahead
if(bytesRead >= 0)
current += bytesRead;
} while(bytesRead > -1);
bos.write(mybytearray,0,current);
bos.flush();
bos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

There are so many problems here that it is difficult to know where to start.
The thread.sleep() in the accept() loop is literally a waste of time. It serves no useful purpose except possibly to throttle the rate at which clients are accepted. If that wasn't your intention, don't do it.
All you are doing when you catch an exception is exiting the server without even printing the exception message. So when something goes wrong, as it is here, you can't possibly know what it was. Don't do that.
readLine() returns null at EOS, on which you must close the socket, stop reading, and exit the thread. You aren't testing that, and you are therefore omitting all three of those required steps. Don't do that.
You are constructing a DataInputStream around a BufferedInputStream for use when reading commands, but you aren't passing it to the methods that process those commands. You are just passing the socket. You are therefore losing data. Don't do that. Every part of the program must use the same input stream or reader for the socket.
You are reading the entire file into memory. This (a) assumes the file size fits into an int; (b) does not scale to large files; (c) wastes space, and (d) adds latency. Don't do that.
You are ignoring the result of the read() into that buffer and assuming it was filled. You can't do that. The correct way to copy streams in Java is shown below. This works with a buffer of any size, e.g. 8192, for an input of any length, and doesn't require you to buffer the entire input into memory. You can use this loop at both the client when sending the file and at the server when receiving it.
while ((count = in.read(buffer)) > 0)
{
out.write(buffer, 0, count);
}
Similarly to (4) above, you are using a DataOutputStream around a BufferedOutputStream for some things and the socket output stream directly for others. Don't do that. All parts of the program must the same output stream or writer for the socket.
You don't need to flush() before close(); it happens automatically.
For some reason after sending the file you are creating a new connection and sending another command. You aren't even closing the connection afterwards. The server will have no easy way of knowing that this connection and this command referred to the file just sent in the code above. It is also redundant, as the receipt of the final EOS tells the server that the file has been sent successfully. Don't do this. If you need to send more information with the file, send it first, before the file, on the same connection.
The reference you cite exhibits many of the above issues. Make an effort to find a reputable starting point.

This is the solution. Please Apply this logic to your code.
I am able to send a file from server to client and client to server.
Check the following code to send the file from Client to Server. It is working great.
If you have any issues let me know.
Server Side Code:
public class ServerRecieveFile {
public static void main(String[] args) throws IOException {// TODO Auto-enerated method stub int filesize=1022386;
int bytesRead; int currentTot= ;
ServerSocket serverSocket=new ServerSocket(15123);
Socket socket=rverSocket.accept();
byte [] bytearray = new byte [filesize];
InputStream is=socket.getInputStream();
File copyFileName=new File("c:/Files Sockets/2.txt");
FileOutputStream fos = new FileOutputStream(copyFileName);
BufferedOutputStream bos = new BufferedOutputStream(fos);
bytesRead = is.read(bytearray,0,bytearray.length);
currentTot = bytesRead;
do {
bytesRead =is.read(bytearray, currentTot, (bytearray.length-currentTot)); if(bytesRead >= 0)
currentTot += bytesRead;
} while(bytesRead > -1);
bos.write(bytearray, 0 , currentTot);
bos.flush();
bos.close();
socket.close();
}
}
Client Side code:
public class ClientSendFile {
public static void main(String[] args) throws UnknownHostException, IOException {// TODO Auto-generated method stub
Client client=new Client();
Socket socket = new Socket(InetAddress.getLocalHost(),15123);
System.out.println("Accepted connection : " + socket);
File transferFile = new File ("c:/Files Sockets/1.txt");
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();
System.out.println("Sending Files...");
os.write(bytearray,0,bytearray.length);
os.flush();
socket.close();
System.out.println("File transfer complete");
}
}

Java Android Sockets

I'm currently working on an Android app which sends an string and a file to a java server app running on remote computer. This java server app should find the index on the file and send back the value of this index (The file structure is: index value. Example: 1 blue) The file is properly sent and received on the remote machine and I have a method which finds the value of the received index on the file. But when I'm trying to send the found value back to the phone I get an exception (closed socket), but I'm not closing the socket or any buffer. I'm not sure if the socket which is closed is the mobile app socket or the java server app socket. I'm using the same socket I use to send to receive (which is the way to work on Android). Sending the answer back to the phone is what my project is missing and is what I need help in. Here is my code:
Client app (Android app):
private class HeavyRemProcessing extends AsyncTask<String, Void, String>
{
protected String doInBackground(String... urls)
{
begins = System.currentTimeMillis();
remoteExecution();
ends= System.currentTimeMillis();
procTime=ends-begins;
aux= Long.toString(procTime);
return aux;
} //doInBackground() ends
protected void onPostExecute(String time)
{
textView1.setText("Result: "+result+". Processing Time: "+time+" milisecs");
}// onPostExecute ends
} //HeavyRemProcessing ends
public void executor(View view)
{
key="74FWEJ48DX4ZX8LQ";
HeavyRemProcessing task = new HeavyRemProcessing();
task.execute(new String[] { "????" });
} //executor() ends
public void remoteExecution()
{
// I have fixed IP and port I just deleted
String ip; //SERVER IP
int port; // SERVER PORT
try
{
cliSock = new Socket(ip, port);
file= new File("/mnt/sdcard/download/Test.txt");
long length = file.length();
byte[] bytes = new byte[(int) length];
FileInputStream fis = new FileInputStream(file);
BufferedInputStream bis = new BufferedInputStream(fis);
BufferedOutputStream out = new BufferedOutputStream(cliSock.getOutputStream());
BufferedReader in = new BufferedReader(new InputStreamReader(cliSock.getInputStream()));
int count;
key=key+"\r\n";
out.write(key.getBytes());
while ((count = bis.read(bytes)) > 0)
{
out.write(bytes, 0, count);
} //It works perfectly until here
//// PROBABLY HERE IS THE PROBLEM:
out.flush();
out.close();
fis.close();
bis.close();
result= in.readLine(); //RECEIVE A STRING FROM THE REMOTE PC
}catch(IOException ioe)
{
// Toast.makeText(getApplicationContext(),ioe.toString() + ioe.getMessage(),Toast.LENGTH_SHORT).show();
}
}catch(Exception exp)
{
//Toast.makeText(getApplicationContext(),exp.toString() + exp.getMessage(),Toast.LENGTH_SHORT).show();
}
} //remoteExecution ends
Java Server App (Remote PC)
public void receivingFile()
{
System.out.println("Executing Heavy Processing Thread (Port 8888).");
try
{
serverSocket = new ServerSocket(8888);
InputStream is = null;
OutputStream os= null;
FileOutputStream fos = null;
BufferedOutputStream bos = null;
BufferedOutputStream boSock =null;
DataOutputStream dataOutputStream=null;
int bufferSize = 0;
try
{
socket = serverSocket.accept();
System.out.println("Heavy Processing Task Connection from ip: " + socket.getInetAddress());
} catch (Exception ex)
{
System.out.println("Can't accept client connection: "+ex);
}
try
{
is = socket.getInputStream();
dataOutputStream = new DataOutputStream(socket.getOutputStream());
bufferSize = socket.getReceiveBufferSize();
}
catch (IOException ex)
{
System.out.println("Can't get socket input stream. ");
}
try
{
fos = new FileOutputStream(path);
bos = new BufferedOutputStream(fos);
}
catch (FileNotFoundException ex)
{
System.out.println("File not found. ");
}
byte[] bytes = new byte[bufferSize];
int count;
System.out.println("Receiving Transfer File!.");
while ((count = is.read(bytes)) > 0)
{
bos.write(bytes, 0, count);
}
System.out.println("File Successfully Received!.");
fos.close();
bos.flush();
bos.close();
is.close();
result= obj.searchIndex();
System.out.println("Found: "+result); //This correctly print the found value
dataOutputStream.writeUTF(result);
dataOutputStream.flush();
dataOutputStream.close();
System.out.println("Data sent back to the Android Client. ");
} catch (IOException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
} // receivingFile() ends
Please if someone can help me I will really appreciate it. I'm thinking is something probably related with the buffers and the socket. My java server app throws an exception: "Closed Socket"... Thanks for your time,
Alberto.

I think your problem is that you closing the outputstream before closing the inputstream. This is a bug in android. Normally in java closing outputstream only flushes the data and closing inputstream causes the connection to be closed. But in android closing the outputstream closes the connection. That is why you are getting closed socket exception,
Put the statements
out.flush();
out.close();
after
result=in.readLine();
or just avoid those statements(out.flush and out.close). I had also faced a similar problem. See my question

Sending Files Through Stream

Here is what I have right now.
Receiver:
public static void read(Socket socket, ObjectInputStream in) {
try {
String separator = in.readUTF();
while (in.readByte() == -3) {
String path = in.readUTF().replaceAll(separator, System.getProperty("file.separator"));
File file = new File(new File(path).getParent());
if (!file.exists()) {
file.mkdirs();
}
FileOutputStream fos = new FileOutputStream(path);
int b = 0;
while ((b = in.readByte()) != -4) {
fos.write(b);
}
fos.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
Sender:
public static void send(String[] path) {
Socket socket;
try {
socket = new Socket(ip, port);
socket.setKeepAlive(true);
} catch (UnknownHostException e) {
return;
} catch (IOException e) {
return;
}
try {
ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
out.writeUTF(Devbox.getSeparator());
for (String s : path) {
send(s, out);
out.writeByte(-2);
}
out.close();
socket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
private static void send(String path, ObjectOutputStream out) {
File file = new File(path);
if (file.isDirectory()) {
File[] files = file.listFiles();
for (File f : files) {
send(path + f.getName(), out);
}
} else {
try {
out.writeByte(-3);
out.writeUTF(path);
FileInputStream fis = new FileInputStream(file);
int b = 0;
while ((b = fis.read()) != -1) {
out.writeByte(b);
}
fis.close();
out.writeByte(-4);
} catch (Exception e) {
e.printStackTrace();
}
}
}
This is the error I get in the sender.
java.net.SocketException: Software caused connection abort: socket write error
at java.net.SocketOutputStream.socketWrite0(Native Method)
at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:109)
at java.net.SocketOutputStream.write(SocketOutputStream.java:153)
at java.io.ObjectOutputStream$BlockDataOutputStream.writeBlockHeader(ObjectOutputStream.java:1874)
at java.io.ObjectOutputStream$BlockDataOutputStream.drain(ObjectOutputStream.java:1855)
at java.io.ObjectOutputStream$BlockDataOutputStream.writeByte(ObjectOutputStream.java:1895)
at java.io.ObjectOutputStream.writeByte(ObjectOutputStream.java:760)
It points to
out.writeByte(b);
It sends about 25 files successfully, then throws this error. The file it throws it on is different each time, but it is in the same range of about 5 files. The receiver stops after one specific file which is usually a couple before the file the sender stops on. It stops because in.readByte() == -3 is false. When it happens, I got numbers like -85 and 16. I tried it on another computer, since it said something about software, and it was the exact same. Does anyone know why this is happening? I've spent a day trying to figure it out, and gotten nowhere. Any help is greatly appreciated.

Please read this answer, I don't think anything else can be said beyond that, also I don't see anything in your code which will close the connection.
From OTN Discussion
WinSock description: The error can occur when the local network system
aborts a connection. This would occur if WinSock aborts an established
connection after data retransmission fails (receiver never
acknowledges data sent on a datastream socket).
TCP/IP scenario: A connection will timeout if the local system doesn't
receive an (ACK)nowledgement for data sent. It would also timeout if a
(FIN)ish TCP packet is not ACK'd (and even if the FIN is ACK'd, it
will eventually timeout if a FIN is not returned).
It seems to happen more with WindowsXP and it seems also to be
possibly related to Windows firewall settings. In any case the salient
point is that the abort has originated inside the local machine.

Use a BufferedInputStream to read the FileInputStream in the send method.
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));
while ((b = bis.read()) != -1) {
out.writeByte(b);
}
Also try a complementary BufferedOutputStream
BufferedInputStream bos = new FileOutputStream(path);
int b = 0;
while ((b = in.readByte()) != -4) {
bos.write(b);
}
In addition, you need to flush out your connections when the file finishes transfer.
out.flush;