Help with TCP Connection

Question

I have a server that works with me and I connect to it by wi-fi but I need help to send commands to it, example sending a message using sockets or something like.

Answer 1

Have this example:

Tcpclient

import android.util.Log;
import java.io.*;
import java.net.InetAddress;
import java.net.Socket;

public class TCPClient {

    private String serverMessage;
    public static final String SERVERIP = "192.168.0.102"; //your computer IP address
    public static final int SERVERPORT = 4444;
    private OnMessageReceived mMessageListener = null;
    private boolean mRun = false;

    PrintWriter out;
    BufferedReader in;

    /**
     *  Constructor of the class. OnMessagedReceived listens for the messages received from server
     */
    public TCPClient(OnMessageReceived listener) {
        mMessageListener = listener;
    }

    /**
     * Sends the message entered by client to the server
     * @param message text entered by client
     */
    public void sendMessage(String message){
        if (out != null && !out.checkError()) {
            out.println(message);
            out.flush();
        }
    }

    public void stopClient(){
        mRun = false;
    }

    public void run() {

        mRun = true;

        try {
            //here you must put your computer's IP address.
            InetAddress serverAddr = InetAddress.getByName(SERVERIP);

            Log.e("TCP Client", "C: Connecting...");

            //create a socket to make the connection with the server
            Socket socket = new Socket(serverAddr, SERVERPORT);

            try {

                //send the message to the server
                out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true);

                Log.e("TCP Client", "C: Sent.");

                Log.e("TCP Client", "C: Done.");

                //receive the message which the server sends back
                in = new BufferedReader(new InputStreamReader(socket.getInputStream()));

                //in this while the client listens for the messages sent by the server
                while (mRun) {
                    serverMessage = in.readLine();

                    if (serverMessage != null && mMessageListener != null) {
                        //call the method messageReceived from MyActivity class
                        mMessageListener.messageReceived(serverMessage);
                    }
                    serverMessage = null;

                }

                Log.e("RESPONSE FROM SERVER", "S: Received Message: '" + serverMessage + "'");

            } catch (Exception e) {

                Log.e("TCP", "S: Error", e);

            } finally {
                //the socket must be closed. It is not possible to reconnect to this socket
                // after it is closed, which means a new socket instance has to be created.
                socket.close();
            }

        } catch (Exception e) {

            Log.e("TCP", "C: Error", e);

        }

    }

    //Declare the interface. The method messageReceived(String message) will must be implemented in the MyActivity
    //class at on asynckTask doInBackground
    public interface OnMessageReceived {
        public void messageReceived(String message);
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
        >
    <ListView android:id="@+id/list"
              android:layout_width="fill_parent"
              android:layout_height="0dip"
              android:layout_weight="1"
              android:transcriptMode="alwaysScroll"
              android:cacheColorHint="#00000000"
              android:listSelector="@android:color/transparent"/>

    <LinearLayout android:id="@+id/footer"
                  android:layout_width="fill_parent"
                  android:layout_height="wrap_content"
                  android:orientation="horizontal"
                  android:gravity="bottom">

        <EditText android:inputType="textMultiLine|textNoSuggestions"
                  android:layout_width="0dp"
                  android:layout_height="40dp"
                  android:id="@+id/editText"
                  android:layout_weight="1"/>

        <Button android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/send_button"
                android:layout_gravity="center_vertical"
                android:text="send" />
    </LinearLayout>
</LinearLayout>

list_item.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout
        xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:id="@+id/list_item"
        android:gravity="center_vertical">

    <TextView android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:id="@+id/list_item_text_view"
              android:textSize="20sp"
              android:padding="10dp"
              android:layout_marginLeft="5dp"/>

</LinearLayout>

Mycustomadapter

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

import java.util.ArrayList;

public class MyCustomAdapter extends BaseAdapter {
    private ArrayList<String> mListItems;
    private LayoutInflater mLayoutInflater;

    public MyCustomAdapter(Context context, ArrayList<String> arrayList){

        mListItems = arrayList;

        //get the layout inflater
        mLayoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    @Override
    public int getCount() {
        //getCount() represents how many items are in the list
        return mListItems.size();
    }

    @Override
        //get the data of an item from a specific position
        //i represents the position of the item in the list
    public Object getItem(int i) {
        return null;
    }

    @Override
        //get the position id of the item from the list
    public long getItemId(int i) {
        return 0;
    }

    @Override

    public View getView(int position, View view, ViewGroup viewGroup) {

        //check to see if the reused view is null or not, if is not null then reuse it
        if (view == null) {
            view = mLayoutInflater.inflate(R.layout.list_item, null);
        }

        //get the string item from the position "position" from array list to put it on the TextView
        String stringItem = mListItems.get(position);
        if (stringItem != null) {

            TextView itemName = (TextView) view.findViewById(R.id.list_item_text_view);

            if (itemName != null) {
                //set the item name on the TextView
                itemName.setText(stringItem);
            }
        }

        //this method must return the view corresponding to the data at the specified position.
        return view;

    }
}

Myactivity

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

import java.util.ArrayList;

public class MyActivity extends Activity
{
    private ListView mList;
    private ArrayList<String> arrayList;
    private MyCustomAdapter mAdapter;
    private TCPClient mTcpClient;

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

        arrayList = new ArrayList<String>();

        final EditText editText = (EditText) findViewById(R.id.editText);
        Button send = (Button)findViewById(R.id.send_button);

        //relate the listView from java to the one created in xml
        mList = (ListView)findViewById(R.id.list);
        mAdapter = new MyCustomAdapter(this, arrayList);
        mList.setAdapter(mAdapter);

        // connect to the server
        new connectTask().execute("");

        send.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                String message = editText.getText().toString();

                //add the text in the arrayList
                arrayList.add("c: " + message);

                //sends the message to the server
                if (mTcpClient != null) {
                    mTcpClient.sendMessage(message);
                }

                //refresh the list
                mAdapter.notifyDataSetChanged();
                editText.setText("");
            }
        });

    }

    public class connectTask extends AsyncTask<String,String,TCPClient> {

        @Override
        protected TCPClient doInBackground(String... message) {

            //we create a TCPClient object and
            mTcpClient = new TCPClient(new TCPClient.OnMessageReceived() {
                @Override
                //here the messageReceived method is implemented
                public void messageReceived(String message) {
                    //this method calls the onProgressUpdate
                    publishProgress(message);
                }
            });
            mTcpClient.run();

            return null;
        }

        @Override
        protected void onProgressUpdate(String... values) {
            super.onProgressUpdate(values);

            //in the arrayList we add the messaged received from server
            arrayList.add(values[0]);
            // notify the adapter that the data set has changed. This means that new message received
            // from server was added to the list
            mAdapter.notifyDataSetChanged();
        }
    }
}

Include in AndroidManifest.xml the following line:

<uses-permission android:name="android.permission.INTERNET" />