Most “internet of things” applications require tcp-ip socket connections to be able to communicate with an android device of course you can do it with http-post/http-get as well but why create unnecessary overhead if it is not needed . Besides that ,we want to communicate real-time and get notifications when something is changing .
One of the problems I came across had to do with the fact that I need to read continuously to make sure I was not missing any messages, and I should be able to stop reading at any time to send messages.
To make the connection I use a socketchannel:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.SocketChannel;
import java.nio.channels.WritableByteChannel;
SocketChannel sc = null;
InetAddress lh;
InetSocketAddress isa;
try {
sc = SocketChannel.open();
sc.configureBlocking(false);
lh = InetAddress.getByName(host);
isa = new InetSocketAddress(lh, port );
sc.connect(isa);
while(!(sc.finishConnect()));
while(!(sc.isConnected()));
while((sc.isConnectionPending()));
} catch (IOException e) {
e.printStackTrace();
}
Now that we have a connection we need to be able to read messages unless we want to send a message , we can do this with help of an asynctask.
private class ReadTask extends AsyncTask<Socket,Integer,Long>
{
int amountofchars=0;
@Override
protected Long doInBackground(Socket... params)
{
String gw,hws,sws,memp;
char[] buf = new char[128];
sk= new SocketClient("192.168.2.31", 6697, "0");
sk.SendPing();
while(true)
{
sk.receiveDataFromServer();
//ChangeValues();
if(sendping)
{
sk.SendPing();
sendping=false;
}
}
}
}
The sk.receiveDataFromServer() contains :
size=sc.read(buffer);
In case we want to send something we can set a boolean value like we do with sendping, sk.SendPing() contains:
sc.write(buffer);
Now we have a very flexible socket solution that enables me to connect with my gateway at any time I want
, but more about that later . I also selected this microcontroller because I have experience with it and the ide is free to download and furthermore I have the jtag here.
