Question

That’s my first question so I hope I write it correctly.

I am trying to send an byte[] array through a Java socket, that array contains an image.

Here is the code to send the file:

public void WriteBytes(FileInputStream dis) throws IOException{
    //bufferEscritura.writeInt(dis.available()); --- readInt() doesnt work correctly
    Write(String.valueOf((int)dis.available()) + "\r\n");
    byte[] buffer = new byte[1024];
    int bytes = 0;
    while((bytes = dis.read(buffer)) != -1){
        Write(buffer, bytes);
    }
    System.out.println("Photo send!");
}
 public void Write(byte[] buffer, int bytes) throws IOException {
    bufferEscritura.write(buffer, 0, bytes);
}
public void Write(String contenido) throws IOException {
    bufferEscritura.writeBytes(contenido);
}

My image:

URL url = this.getClass().getResource("fuegos_artificiales.png");
FileInputStream dis = new FileInputStream(url.getPath());
sockManager.WriteBytes(dis);

My code to get the image file:

public byte[] ReadBytes() throws IOException{
DataInputStream dis = new DataInputStream(mySocket.getInputStream());
int size = Integer.parseInt(Read());
System.out.println("Recived size: "+ size);
byte[] buffer = new byte[size];
System.out.println("We are going to read!");
dis.readFully(buffer);
System.out.println("Photo received!");
return buffer;

}

public String Leer() throws IOException {
    return (bufferLectura.readLine());
}

And to create an image file:

byte[] array = tcpCliente.getSocket().LeerBytes();
FileOutputStream fos = new FileOutputStream("porfavor.png");
try {
    fos.write(array);
}
finally {
    fos.close();
}

The image file is created but when I try to open it for example with Paint it says that it can’t open it because it is damaged…
I also tried to open both images (the original and the new one) with notepad and they have the same data inside!

I don’t know what is happening…

I hope you help me.

Thanks!

Answer 1

1. Don’t use available() as a measure of file length. It isn’t. There is a specific warning in the Javadoc about that.

2. Use DataOutputStream.writeInt() to write the length, and DataInputStream.readInt() to read it, and use the same streams to read the image data. Don’t use multiple streams on the same socket.

Also in this:

URL url = this.getClass().getResource("fuegos_artificiales.png");
FileInputStream dis = new FileInputStream(url.getPath());

the second line should be:

InputStream in = URL.openConnection.getInputStream();

A class resource is not a file.