Develop Reference

Java socket getting only NUL characters after writing byte array

I'm trying to send files in chunks from a client to server via byte arrays. I'm using ObjectInputStream. The write works and the filesize matches but when I open the file, I only get a blank textfile(which when opened in a IDE, shows NUL,NUL,NUL...).
Server code:
try(
FileOutputStream fileOut = new FileOutputStream(file);
ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
){
byte[] arr = new byte[chunkSize];
try {
int len = 0;
long bytesRead = 0;
byte[] bytes = new byte[chunkSize];
int chunkNo = 1;
while(true)
{
len = in.read(bytes,0, chunkSize);
System.out.println();
if(len < 0)
break;
fileOut.write(arr, 0, len);
bytesRead += len;
out.writeObject(Server.CHUNK_ACKNOWLEDGE_MSG);
String ackReply = (String) in.readObject();
if(ackReply.equalsIgnoreCase((Server.UPLOAD_ACKNOWLEDGE_RECEIVE_TIMEOUT_MSG))){
if(Server.DEBUG)
System.out.println(fileName + " send timeout.");
deleteFile();
break;
}else if (ackReply.equalsIgnoreCase(Server.UPLOAD_COMPLETE_MSG)){
if(bytesRead != fileSize){
System.out.println(fileName + " File size mismatch");
deleteFile();
break;
}else{
System.out.println( fileName + " File written");
break;
}
}
}
}catch (IOException ioe){
if(Server.DEBUG)
ioe.printStackTrace();
}
Client code:
try(
FileInputStream fileInput = new FileInputStream(file);
ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
){
byte[] arr = new byte[chunkSize];
try {
int len = 0;
int bytesRead = 0;
int chunkCount = 1;
while((len = fileInput.read(arr, 0, chunkSize)) != -1)
{
out.write(arr, 0, len);
out.flush();
bytesRead += len;
}
try {
System.out.println("wait ack");
socket.setSoTimeout(timeout);
String ack = (String) in.readObject();
System.out.println(ack);
if(bytesRead >= fileSize){
out.writeObject(Server.UPLOAD_COMPLETE_MSG);
System.out.println(Server.UPLOAD_COMPLETE_MSG);
break;
}else{
out.writeObject(Server.CHUNK_ACKNOWLEDGE_MSG);
}
}catch (SocketTimeoutException e){
out.writeObject(Server.UPLOAD_ACKNOWLEDGE_RECEIVE_TIMEOUT_MSG);
System.out.println(Server.UPLOAD_ACKNOWLEDGE_RECEIVE_TIMEOUT_MSG);
break;
}finally {
socket.setSoTimeout(0);
}
}
}
}catch (IOException ioe){
ioe.printStackTrace();
}
}catch (FileNotFoundException fnfe){
System.out.println("No such file: " + fileName);
}catch (Exception e){
e.printStackTrace();
}
finally {
try {
socket.close();
}catch (Exception ex){
ex.printStackTrace();
}
}
I tried writing the byte array to another file on the client side and the copy was identical. So the problem must be during sending data over socket.
The Server.X_MSG is just a constant string. I don't know if mixing readobject() and read(bytearray) on the same ObjectInputStream causes any issues though.

Maybe it's because fileOut.write(arr, 0, len); use arr and len = in.read(bytes,0, chunkSize); use bytes? They are not the same array.

Why socket send only 1KB (425B) of data?

I am learning sockets and now I want to write file transfer program. I have server part and client part. Server part contains 2 ports: 5000 (commands) and 5001 (files). Now I want to send a file via socket and when I did something is wrong because only 425B of data is sending.
Here is client send method:
private void sendFile(Socket socket) {
File file2 = new File("C:\\Users\\barte\\Desktop\\dos.png");
byte[] bytes = new byte[16 * 1024];
System.out.println(file2.exists());
try (InputStream inputStream = new FileInputStream(file2);
OutputStream outputStream = socket.getOutputStream();
OutputStream secondOutput = new FileOutputStream("C:\\Users\\barte\\Desktop\\received\\dos.png")) {
int count;
while ((count = inputStream.read(bytes)) > 0) {
outputStream.write(bytes, 0, count);
secondOutput.write(bytes, 0, count);
}
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
As you can see (image below) I am writing this file also locally and everything is ok, all of 73KB of data is writed.
Now, on server side I am trying to receive this file:
case SEND: {
new Thread(() -> {
printWriter.println("Server is receiving files right now...");
try (ServerSocket serverSocket = new ServerSocket(5001)) {
while (true) {
new FilesTransfer(serverSocket.accept()).start();
}
} catch (IOException e) {
e.printStackTrace();
}
}).start();
break;
}
And inside FilesTransfer run method:
#Override
public void run() {
System.out.println("Hello there");
try {
InputStream inputStream = inSocket.getInputStream();
OutputStream outputStream = new FileOutputStream("C:\\Users\\barte\\Desktop\\received\\file");
byte[] bytes = new byte[16 * 1024];
int count;
while ((count = inputStream.read()) > 0) {
outputStream.write(bytes, 0, count);
}
outputStream.close();
inputStream.close();
inSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Where is a bug? Why only empty bytes are sending when locally everything it's fine?

The problem is:
while ((count = inputStream.read()) > 0) {
Your code uses InputStream.read(), which reads individual bytes (or -1 when end-of-stream). Right now, you are reading individual bytes, interpreting that as a length, and then writing that number of 0x00 bytes from bytes to the file. This stops when you read a 0x00 byte from the stream.
You need to change this to use InputStream.read(byte[]):
while ((count = inputStream.read(bytes)) != -1) {
That is, you need to pass bytes in, and check for the result being unequal to -1, not if it is greater than zero (0), although read(byte[]) will only return 0 if the passed in byte array has length zero, so that is not a real concern.

You could do it in this way:
#Override
public void run() {
System.out.println("Hello there");
try {
InputStream inputStream = inSocket.getInputStream();
OutputStream outputStream = new FileOutputStream("C:\\Users\\barte\\Desktop\\received\\file");
byte[] bytes = new byte[16 * 1024];
int byteRead= 1;
while (byteRead > -1) {
byteRead= inputStream.read();
outputStream.write(byteRead);
}
outputStream.close();
inputStream.close();
inSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
Actually END OF FILE or EOF means -1 and you did > 0 so 0 was taken and it stopped the connection saving the file.
I also recommend to write a logic to transfer the filename as a command to the server so that the file is saved with the correct name and extension!

inputStream read method constantly reading 0 [duplicate]

This question already has answers here:
Java multiple file transfer over socket
(3 answers)
Closed 6 years ago.
I am first transferring a file from a client to my master, the stores the byte array and then sends to the slave. Where the slave stores the byte array. But when The file is sent properly from client to master but when I send the byte array to the slave it to the slave the read method in input stream constantly reads 0.
// This method writes the file to the master
public void writeFile(File file) {
try {
this.write(String.valueOf(file.length()));
byte[] bytearray = new byte[(int) file.length()];
FileInputStream fin = new FileInputStream(file);
BufferedInputStream bin = new BufferedInputStream(fin);
bin.read(bytearray, 0, bytearray.length);
BufferedOutputStream bos;
OutputStream os = socket.getOutputStream();
bos= new BufferedOutputStream(os);
bos.write(bytearray, 0, bytearray.length);
bos.flush();
} catch (IOException e) {
e.printStackTrace();
}
}
//This method reads the file into the master as a byte array and the byte array from the master into slave
public byte[] readFile() {
byte[] bytearray = null;
try {
int currentTot = 0;
int filesize = Integer.parseInt(this.read());
System.out.println(filesize);
bytearray = new byte[filesize];
InputStream is = socket.getInputStream();
int bytesRead;
bytesRead = is.read(bytearray, 0, bytearray.length);
currentTot = bytesRead;
int count = 0;
do {
bytesRead = is.read(bytearray, currentTot, (bytearray.length - currentTot));
if (bytesRead > 0) {
currentTot += bytesRead;
count = 0;
} else {
count++;
System.out.println("count " + count);
}
} while (bytesRead > -1);
System.out.println(currentTot);
// bos.write(bytearray, 0, currentTot);
// bos.flush();
// bos.close();
} catch (IOException e) {
e.printStackTrace();
}
return bytearray;
}
//This method writes from the master to the slave
public void writeByte(byte[] m) {
this.write(String.valueOf(m.length));
System.out.println("File side inside sender" + m.length);
// byte[] bytearray = m;
OutputStream os;
try {
os = socket.getOutputStream();
os.write(m, 0, m.length);
os.flush();
//os.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
Interestingly if I close my output stream after I send my byte array from my master it works well. But I cannot close stream because the slave needs to communicate with the master further. Thanks in advance.
public void write(String output) {
if (pw == null)
this.openWriter();
pw.println(output);
}
public String read() {
try {
if (br == null) {
if (this.socket != null)
br = new BufferedReader(new InputStreamReader(this.socket.getInputStream()));
}
return br.readLine();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}

You're misreading the file length in the receiver. You are getting zero, so you're constructing a zero length byte array, so read() returns zero.
You need to send the length via DataOutputStream.writeLong() and read it via DataInputStream.readLong(). And then your sending and receiving code is all wrong as well. See my answer here for complete code.

how to pass audio between sockets in java

Im try to pass audio between sockets but it pass one time in client than clients stops working.
I think the way im writing and sending may be wrong please help me regarding this code
Following is my server code :
public void run(){
try{
SetInitialSettings();
int bufferSize = (int) format.getSampleRate() * (int) format.getFrameSize();
System.out.println("length :" +bufferSize);
out = new ByteArrayOutputStream();
readagain=true;
while(record){
int count=0;
for(int i=0;i<1000;i++)
{
if(buffer==null){
buffer = new byte[bufferSize];
}
count = line.read(buffer, 0, buffer.length);
if (count > 0) {
//out.write(buffer, 0, count);
//readagain=false;
for (int j=0;i<ser.clientReceiver.audioSender.size();j++){
ser.clientReceiver.audioSender.get(i).cliOut.write("Audio".getBytes());
ser.clientReceiver.audioSender.get(i).cliOut.write('\n');
ser.clientReceiver.audioSender.get(i).cliOut.flush();
ser.clientReceiver.audioSender.get(i).cliOut.write(buffer,0,count);
ser.clientReceiver.audioSender.get(i).cliOut.flush();
Thread.sleep(2000);
}
}
}
}
}
catch(Exception ex)
{
System.out.println(ex.getMessage());
}
}
and following is my client code :
public void run(){
try{
//audioReceiver = new TAudioReceiver(cli);
//audioReceiver.start();
while(true){
//Thread.sleep(1000);
System.out.println("reading token");
cmd= cli.BufferedReader().readLine();
System.out.println("token :" +cmd);
switch (cmd) {
case "Msg":
message = cli.BufferedReader().readLine();
cmd="None";
break;
case "File":
GetFile();
break;
case "Audio":
PlayAudio();
break;
}
}
//reading msgs here
}
catch(Exception ex)
{
//throw new InterruptedException(ex.getMessage());
}
}
this is the function need to run when "audio" msg received from server to client
public void PlayAudio()throws Exception{
try{
cli.ServerInputStream().read(buffer);
audio = buffer;
audioIn = new ByteArrayInputStream(audio);
AudioFormat f = new AudioFormat(8000, 8, 1,true, true);
ain= new AudioInputStream(audioIn,f, audio.length/f.getFrameSize());
DataLine.Info info = new DataLine.Info(SourceDataLine.class, f);
try (SourceDataLine line = (SourceDataLine)AudioSystem.getLine(info)) {
int bufferSize = (int) f.getSampleRate()* f.getFrameSize();
buffer= new byte[bufferSize];
int count;
while ((count = ain.read(buffer, 0, buffer.length)) != -1) {
if (count > 0) {
line.write(buffer, 0, count);
}
}
line.drain();
}
}
catch(Exception ex)
{
System.out.println("file" + ex.getMessage());
}
}

Your original code was better. You must write(buffer, 0, count), not write(buffer). Otherwise you are writing junk at the end of each buffer that wasn't read by the last read. Your second piece of code ignores the result of read().

Knowing How to Detect a Disconnection when Reading Socket Data (InputStream)

I have a thread that is constantly reading data from an InputStream. The InputStream data is coming from a Bluetooth socket. Previously, I wasn't using the if(mmInStream.available() > 0) around the InputStream read statement and when the bluetooth socket went away (someone turned off the device), the mmInStream.read would throw a IOException and then I could process my disconnection logic. What is the best way to determine when a disconnect has occurred?
First byte of 0xEE tells me its the leader of the data packet and the second tells me the length to read.
public void run() {
byte[] tempBuffer = new byte[1024];
byte[] buffer = null;
int byteRead=0;
long timeout=0;
long wait=100;
while (true) {
try {
timeout = System.currentTimeMillis() + wait;
if(mmInStream.available() > 0) {
while((mmInStream.available() > 0) && (tempBuffer[0] != (byte) 0xEE) && (System.currentTimeMillis() < timeout)){
byteRead = mmInStream.read(tempBuffer, 0, 1);
}
if(tempBuffer[0] == (byte) 0xEE){
timeout = System.currentTimeMillis() + wait;
while(byteRead<2 && (System.currentTimeMillis() < timeout)){
byteRead += mmInStream.read(tempBuffer, 1, 1);
}
}
timeout = System.currentTimeMillis() + wait;
while((byteRead<tempBuffer[1]) && (System.currentTimeMillis() < timeout)){
byteRead += mmInStream.read(tempBuffer, byteRead, tempBuffer[1]-byteRead);
}
}
if(byteRead > 0){
//do something with the bytes read in
}
}
catch (IOException e) {
bluetoothConnectionLost();
break;
}
}
}

You don't need all this malarkey with available(). Just set a read timeout with setSoTimeout, read, detect read returning -1, use the count returned by read if > 0 rather than assuming the buffer got filled, catch SocketTimeoutException to detect read timeouts, and catch IOException to detect other breakages.

After a look at the documentation, I think it's like this:
public void run() {
byte[] tempBuffer = new byte[1024];
int byteRead = 0;
while (true) {
try {
bytesRead = mmInStream.read(tempBuffer, 0, tempBuffer.length);
if (bytesRead < 0)
// End of stream.
break;
// Do something with the bytes read in. There are bytesRead bytes in tempBuffer.
} catch (IOException e) {
bluetoothConnectionLost();
break;
}
}
}

I think it's like this:
void fun(){
isOpen = true;
try{
InputStream stream = socket.getInputStream();
while(isOpen){
byte[] buf = new byte[8];
int pos = stream.read(buf);
if (pos < 0) {
throw new IOException();
}
//dosomething...
}
}catch(IOException e) {
isOpen = false;
}finally{
//do dispose here
}
}