Creating a singleton for maintaining TCP socket connection across different activities in Android

Question

As the title suggests, I am trying to create a singleton class for maintaining a TCP socket across different activities in my application. I am almost an absolute beginer to this and would really appreciate someone pointing me in the right direction.

UPDATE:

Here is the code for the class that I wrote:

public static ConnectionManager getInstance() {
    if(instance == null) {
    instance = new ConnectionManager();
    }
   return instance;
}



public void send(String str){

    try{
        PrintWriter out = new PrintWriter(new BufferedWriter(
        new OutputStreamWriter(access_point.getOutputStream())),true);
        out.println(str);
    }

    catch(IOException e){       
        e.printStackTrace();
    }


}

}

AND HERE IS HOW I CALLED IT ON ONE OF THE ACTIVITIES

private static ConnectionManager command = ConnectionManager.getInstance();
.........
command.send("Turn on");