如何使用后台线程检查套接字是否已连接

Question

i am developing application in which i am checking availability of port before reading and writing on socket. i am using following code to check status

private boolean isAvailable(String host, int port) {
        try {
            Socket socket = new Socket();
            socket.connect(new InetSocketAddress(host, port), 1000);
            isPortAvailable = socket.isConnected();
        } catch (IOException e) {
            isPortAvailable = false;
        }
        return isPortAvailable;
    }

After this i am checking this status on onClick()

if (isAvailable(ip, Integer.parseInt(portLVR))) {
    startActivity(new Intent(getApplicationContext(),ActivityLivingRoom.class));
} else
    Toast.makeText(getApplicationContext(),"Connection Error !", Toast.LENGTH_SHORT).show();

but my problem is if i check this status on main thread then android will give me networkonMainThradException so how do i manage this operation using background thread?

Answer 1

Try this

 private class SocketCheckTask extends AsyncTask<String , Integer , Boolean> {
       String classname="";
     public SocketCheckTask (String classname) {
              this.classname=classname;
    } 
@Override
protected Boolean doInBackground(String... params) {
    return isAvailable(params[0], Integer.parseInt(params[1]);
  }

@Override
protected void onPostExecute(Boolean isAvailable) {
   if (isAvailable)) {
     Class c=Class.forName("yourpackage"+classname);
startActivity(new Intent(getApplicationContext(),c));
     } else
Toast.makeText(getApplicationContext(),"Connection Error !", Toast.LENGTH_SHORT).show();
     }
}

And send it like this

 SocketCheckTask task=new SocketCheckTask ("ActivityLivingRoom");
task.execute(ipadress,port);

Answer 2

Like this:

private class CheckAvailabilityTask extends AsyncTask<Void, Void, Boolean> {
    String ip;
    int port;

    public CheckAvailabilityTask(String ip, int port) {
        this.ip = ip;
        this.port = port;
    }
    @Override
    protected Boolean doInBackground(Void... params) {
        return isAvailable(this.ip, this.port);
    }

    @Override
    protected void onPostExecute(Boolean isAvailable) {
        if (iisAvailable) {
            startActivity(new Intent(getApplicationContext(),ActivityLivingRoom.class));
        } else
        Toast.makeText(getApplicationContext(),"Connection Error !", Toast.LENGTH_SHORT).show();
    }
}

And in onClick() event:

new CheckAvailabilityTask(IP, PORT).execute();

Answer 3

I think best solution would be, start a new thread on click event and putting your start activity code inside the same thread.

If you are using toast you can do it from that thread but if you plan to update UI (like red/green status) you have to use handler and messages.

FYI, Asynctask just remove the implementation of Thread and shows people a nice abstraction.

Answer 4

You can't open a socket and never close it just to establish whether a host:port is available.

The only real way to test whether any service or resource is available is to try to use it.

Just do the connect, and the I/O, when you need to do them, and handle the resulting exceptions at that point. You have to catch them anyway.

Don't write code that tries to predict the future.