Question

So i want to make one application send data to the other via wi-fi. Since IPs are private, for the devices that are used to run the apps on, i figured i should go with something like this in order to make the two apps communicate:

App1<——>RemoteServer<——->App2

I need help to setup the server that would just receive data from App1 and forward them to App2. I suppose i should use sockets for both apps, do i have to use 2 sockets? How do i pass the data that i receive from app1 to app2?

I will be using Java.

Ty in advance.

Answer 1

Yes, two sockets would be the right thing (if you don’t want to tunnel via HTTP or similar).

public void proxy() {
    ServerSocket s = ...;
    Socket app1 = s.accept();
    Socket app2 = s.accept();
    InputStream app1Input = app1.getInputStream();
    InputStream app2Input = app2.getInputStream();
    OutputStream app1Output = app1.getOutputStream();
    OutputStream app2Output = app2.getOutputStream();

    pipeInToOut(app1Input, app2Output);
    pipeInToOut(app2Input, app1Output);
}

public void pipeInToOut(final InputStream in, final OutputStream out) {
    new Thread() { public void run() {
       byte[] buffer = new byte[2000];
       int r;
       while((r = in.read(buffer) > 0) {
          out.write(buf, 0, r);
       }
    }}.start();
}

Add some exception handling, stream closing and logic 🙂