How to download two or multiple files at a time in Android using NanoHTTPD?

Question

I use NanoHTTPD as web server in my Android app.

I pass two file names from client browser to NanoHTTPD server, and I hope to download the two files at a time, but the following code only download the file1, and the file2 isn't downloaded.

How to download two or multiple files at a time?

public class MyWebServer extends NanoHTTPD
{

    private final String rootDir;

    public MyWebServer(int port, String rootDir)
    {
        super("192.168.1.4", port);
        this.rootDir = rootDir;
    }

    @Override
    public Response serve(IHTTPSession session)
    {       
        Map<String, String> parms = session.getParms();

        String filename1=GetFilename(parms);
        String filename2=GetFilename(parms);

        File file1 = new File(rootDir + filename1);
        File file2 = new File(rootDir + filename2);

        return downloadFile(file1);
        return downloadFile(file2);
    }


    private Response downloadFile(File file)
    {
        FileInputStream fis = null;
        try
        {
            fis = new FileInputStream(file);
        } catch (FileNotFoundException ex)
        {
            Logger.getLogger(MyWebServer.class.getName()).log(Level.SEVERE, null, ex);
        }
        return newFixedLengthResponse(Response.Status.OK, "application/octet-stream", fis, file.getTotalSpace());
    }



    @Override
    public Response newFixedLengthResponse(IStatus status, String mimeType, String message)
    {
        Response response = super.newFixedLengthResponse(status, mimeType, message);
        response.addHeader("Accept-Ranges", "bytes");
        return response;
    }


}

Answer 1

Below NanoHTTPD constructor creates an async task when you call super(..) in the MyWebServer constructor.

public NanoHTTPD(String hostname, int port) {
        this.hostname = hostname;
        this.myPort = port;
        setTempFileManagerFactory(new DefaultTempFileManagerFactory());
        setAsyncRunner(new DefaultAsyncRunner());

        // creates a default handler that redirects to deprecated serve();
        this.httpHandler = new IHandler<IHTTPSession, Response>() {

            @Override
            public Response handle(IHTTPSession input) {
                return NanoHTTPD.this.serve(input);
            }
        };
    }

So the answer must be to have one downloadFile() for each operation. That is to say you should call new MyWebServer() to start each download task.

@Override
    public Response serve(IHTTPSession session)
    {       
        Map<String, String> parms = session.getParms();

        String filename=GetFilename(parms);

        File file = new File(rootDir + filename);

        return downloadFile(file);
    }

EDIT:

By using 2 instance of MyWebServer class, u can listen to client requests for each of 2 params. (I didn't try this but it must work and I recommend you should send multiple requests on the client side and one webserver instance on the server side).

public class MyWebServer extends NanoHTTPD
{

    private final String rootDir;
    private final int param_type = 1; //default 1

    public MyWebServer(int port, String rootDir, int param)
    {
        super("192.168.1.4", port);
        this.rootDir = rootDir;
        this.param_type = param;
    }

    @Override
    public Response serve(IHTTPSession session)
    {       
        Map<String, String> parms = session.getParms();
        File file;

        if (param_type == 1){
             String filename=parms.get("param1");
             file = new File(rootDir + filename);
        }else if(param_type == 2){ 
             String filename=parms.get("param2");
             file = new File(rootDir + filename);
        }


        return downloadFile(file);
    }


    private Response downloadFile(File file)
    {
        FileInputStream fis = null;
        try
        {
            fis = new FileInputStream(file);
        } catch (FileNotFoundException ex)
        {
            Logger.getLogger(MyWebServer.class.getName()).log(Level.SEVERE, null, ex);
        }
        return newFixedLengthResponse(Response.Status.OK, "application/octet-stream", fis, file.getTotalSpace());
    }



    @Override
    public Response newFixedLengthResponse(IStatus status, String mimeType, String message)
    {
        Response response = super.newFixedLengthResponse(status, mimeType, message);
        response.addHeader("Accept-Ranges", "bytes");
        return response;
    }


}

In MainActivity.java

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        MyWebServer server1 = new MyWebServer(port, rootDir, 1);
        MyWebServer server2 = new MyWebServer(port, rootDir, 2);

        server1.start();
        server2.start();

    }