How to download an image with Sockets

Question

So I'm doing the exercise of getting an image from the web using Sockets. I'm not sure which class to use when storing bytes of an image to then create the file. My code so far is:

    import java.io.*;
    import java.net.*;
    import java.awt.image.*;
    import javax.imageio.stream.ImageInputStream;
    import javax.imageio.ImageIO;

    class MyClass{
        public static void main(String[] args)throws IOException{
            Socket s = new Socket();
            ImageInputStream s_in = null; //I'm not sure about this
            PrintWriter s_out = null;

            try{
                s.connect(new InetSocketAddress("data.pr4e.org",80));
                System.out.println("Connected");

                s_out = new PrintWriter(s.getOutputStream(), true);

                s_in = ImageIO.createImageInputStream(s.getInputStream());//nor this
            }
            catch (UnknownHostException e){
                System.err.println("Don't know about host");
                System.exit(1);
            }

            //Message to server
            String message = "GET http://data.pr4e.org/cover3.jpg HTTP/1.0\r\n\r\n";
            s_out.println(message);

            //This is where it gets confusing
            OutputStream out = null;
            while (true){
            try{
            out = new BufferedOutputStream(new 
            FileOutputStream("C:\\Users\\Steff\\Desktop\\Java ejemplos\\cover3.jpg"));
            out.write(s_in.read());
            }
            finally{
              if(out != null){
              out.close();
           }  
        }
    }
}

}

score 0 · Accepted Answer · answered Aug 01 '18 at 23:22

I fixed your code a bit. It saves all the data to file.

public static void main(String[] args) throws IOException {
    Socket s = new Socket();
    InputStream s_in = null;
    PrintWriter s_out = null;

    try {
        s.connect(new InetSocketAddress("data.pr4e.org", 80));
        System.out.println("Connected");
        s_out = new PrintWriter(s.getOutputStream(), true);
        s_in = s.getInputStream();
    } catch (UnknownHostException e) {
        System.err.println("Don't know about host");
        System.exit(1);
    }

    // Message to server
    String message = "GET http://data.pr4e.org/cover3.jpg HTTP/1.0\r\n\r\n";
    s_out.println(message);

    OutputStream out = new BufferedOutputStream(new FileOutputStream("C:\\Users\\Steff\\Desktop\\Java ejemplos\\cover3.jpg"));
    int count;
    byte[] buffer = new byte[4096];
    while ((count = s_in.read(buffer)) > 0) {
        out.write(buffer, 0, count);
    }
    out.close();
}

Unfortunately the image is not readable. Why? Because saved data contains whole stream along with HTTP response. That's what you get for using sockets without using some HTTP-aware library like Apache HttpClient. You can open file using any text editor to see the contents.

If you're really sure and want to continue using sockets please consult possible duplicate linked by gtgaxiola. It contains more code to cope with separating headers from actual data.

How to download an image with Sockets

1 Answers1