removing delay in sending string through tcp/ip

Question

My project has a light switch which has an IP address and port and accepts strings to control. I am trying to create an application to switch this on and off. My code works, however after the first click, there is a significant delay between the next click and the switch actually switching.

I have a button for on and off. main.java:

package com.android.lswitch;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class lightswitch extends Activity {
/** Called when the activity is first created. */

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

    // Handle swon button
    Button swon = (Button) findViewById(R.id.swon);
    swon.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            sw(true);
        }
    });

    // Handle swoff button
    Button swoff = (Button) findViewById(R.id.swoff);
    swoff.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            sw(false);
        }
    });


}

private void sw(boolean swstate) {
    if (swstate == true) {
        Thread swonThread = new Thread(new swon());
        swonThread.start();    
    }

    if (swstate == false) {
    Thread swoffThread = new Thread(new swoff());
    swoffThread.start();    
    }

}
}

and button on java: package com.android.lswitch;

import java.io.BufferedWriter;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;

public class swon implements Runnable {
public static final String SERVERIP = "10.0.0.25";
public static final int SERVERPORT = 4000;


public void run(){
try {
    InetAddress serverAddr = InetAddress.getByName(SERVERIP);

    Socket socket = new Socket(serverAddr, SERVERPORT);

    String swon = "A55A6B0550000000FFFBDE0030C8";
    String but0 = "A55A6B0500000000FFFBDE002066";

    PrintWriter out = new PrintWriter( new BufferedWriter
            ( new OutputStreamWriter(socket.getOutputStream())),true);

    out.println(swon);
    out.println(but0);
    socket.close();
} catch(Exception e) {
}
    finally {

    }
}
}

button off is virtually the same but with different strings. I'm new to android coding (and java coding) so can't see where the hold up is. Do I need to flush the strings somewhere? or is there a better way of tackling this project?

Cheers

Answer 1

PrintWriter may be buffered, so you should definitely flush() it before issuing any close() operation on the underlying socket.

It is also preferable to call PrintWriter.close() instead of Socket.close() , eg, in a finally block, such as:

PrintWriter out = new PrintWriter( new BufferedWriter
        ( new OutputStreamWriter(socket.getOutputStream())),true);

try {
  out.println(swon);
  out.println(but0);
  out.flush();
} finally {
  out.close();
}