What is a simple way to implement a websocket client in Android? Is the following example correct?

android websocket network-programming java-websocket
Kreshnik picture Kreshnik · Dec 7, 2015 · Viewed 48.9k times · Source

I was trying to use a class that implements a WebSocket client in Android. But I get the following error: 

12-07 11:22:46.286 31579-31579/com.domain.wsocketchat W/System: ClassLoader referenced unknown path: /data/app/com.domain.wsocketchat-2/lib/arm
12-07 11:22:46.392 31579-31579/com.domain.wsocketchat W/System.err: an error occurred:java.net.SocketException: socket failed: EACCES (Permission denied)

The class that I'm using follows: 

import org.java_websocket.client.WebSocketClient;
import org.java_websocket.drafts.Draft;
import org.java_websocket.drafts.Draft_10;
import org.java_websocket.handshake.ServerHandshake;

import java.net.URI;

public class EmptyClient extends WebSocketClient {
    public EmptyClient(URI serverUri, Draft draft) {
        super(serverUri, draft);
    }

    public EmptyClient(URI serverURI) {
        super(serverURI);
    }

    @Override
    public void onOpen(ServerHandshake handshakedata) {
        System.out.println("new connection opened");
    }

    @Override
    public void onClose(int code, String reason, boolean remote) {
        System.out.println("closed with exit code " + code + " additional info: " + reason);
    }

    @Override
    public void onMessage(String message) {
        System.out.println("received message: " + message);
    }

    @Override
    public void onError(Exception ex) {
        System.err.println("an error occurred:" + ex);
    }
}

The class is called within the onCreate():

WebSocketClient client = null;
try {
    client = new EmptyClient(new URI("ws://192.168.1.135:9000/server.php"), new Draft_10());
} catch (URISyntaxException e) {
    e.printStackTrace();
}
client.connect();

AndroidManifest: 

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

Sdk: minSdkVersion 16

Anyone have any idea, what could be the problem? It seems everything allright! Thank you in advance.

Answer

Kreshnik picture Kreshnik · Dec 7, 2015

I already resolved the problem by using another class, that handles the websocket client: 

    import android.app.Activity;
    import android.app.Fragment;
    import android.os.Build;
    import android.os.Bundle;
    import android.util.Log;
    import android.view.LayoutInflater;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.EditText;
    import android.widget.TextView;

    import org.java_websocket.client.WebSocketClient;
    import org.java_websocket.handshake.ServerHandshake;

    import java.net.URI;
    import java.net.URISyntaxException;

    public class MainActivity extends Activity {
        private WebSocketClient mWebSocketClient;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);

            connectWebSocket();

            if (savedInstanceState == null) {
                getFragmentManager().beginTransaction()
                        .add(R.id.container, new PlaceholderFragment())
                        .commit();
            }
        }


        @Override
        public boolean onCreateOptionsMenu(Menu menu) {

            // Inflate the menu; this adds items to the action bar if it is present.
            getMenuInflater().inflate(R.menu.main, menu);
            return true;
        }

        @Override
        public boolean onOptionsItemSelected(MenuItem item) {
            // Handle action bar item clicks here. The action bar will
            // automatically handle clicks on the Home/Up button, so long
            // as you specify a parent activity in AndroidManifest.xml.
            switch (item.getItemId()) {
                case R.id.action_settings:
                    return true;
            }
            return super.onOptionsItemSelected(item);
        }

        /**
         * A placeholder fragment containing a simple view.
         */
        public static class PlaceholderFragment extends Fragment {

            public PlaceholderFragment() {
            }

            @Override
            public View onCreateView(LayoutInflater inflater, ViewGroup container,
                    Bundle savedInstanceState) {
                View rootView = inflater.inflate(R.layout.fragment_main, container, false);
                return rootView;
            }
        }

        private void connectWebSocket() {
            URI uri;
            try {
                uri = new URI("ws://192.168.1.135:9000/");
            } catch (URISyntaxException e) {
                e.printStackTrace();
                return;
            }

            mWebSocketClient = new WebSocketClient(uri) {
                @Override
                public void onOpen(ServerHandshake serverHandshake) {
                    Log.i("Websocket", "Opened");
                    mWebSocketClient.send("Hello from " + Build.MANUFACTURER + " " + Build.MODEL);
                }

                @Override
                public void onMessage(String s) {
                    final String message = s;
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            TextView textView = (TextView)findViewById(R.id.messages);
                            textView.setText(textView.getText() + "\n" + message);
                        }
                    });
                }

                @Override
                public void onClose(int i, String s, boolean b) {
                    Log.i("Websocket", "Closed " + s);
                }

                @Override
                public void onError(Exception e) {
                    Log.i("Websocket", "Error " + e.getMessage());
                }
            };
            mWebSocketClient.connect();
        }

        public void sendMessage(View view) {
            EditText editText = (EditText)findViewById(R.id.message);
            mWebSocketClient.send(editText.getText().toString());
            editText.setText("");
        }
    }

For anyone that is interested, I've used a Websocket-ChatServer written in PHP: 

<?php
$r = $_SERVER['SERVER_ADDR'];
if($r=="::1") $r="localhost";

$host = $r; //'localhost'; //host
$port = '9000'; //port
$null = NULL; //null var

//Create TCP/IP sream socket
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
//reuseable port
socket_set_option($socket, SOL_SOCKET, SO_REUSEADDR, 1);

//bind socket to specified host
socket_bind($socket, 0, $port);

//listen to port
socket_listen($socket);

//create & add listning socket to the list
$clients = array($socket);

//start endless loop, so that our script doesn't stop
while (true) {
    //manage multipal connections
    $changed = $clients;
    //returns the socket resources in $changed array
    socket_select($changed, $null, $null, 0, 10);

    //check for new socket
    if (in_array($socket, $changed)) {
        $socket_new = socket_accept($socket); //accpet new socket
        $clients[] = $socket_new; //add socket to client array

        $header = socket_read($socket_new, 1024); //read data sent by the socket
        perform_handshaking($header, $socket_new, $host, $port); //perform websocket handshake

        socket_getpeername($socket_new, $ip); //get ip address of connected socket
        $response = mask(json_encode(array('type'=>'system', 'message'=>$ip.' connected'))); //prepare json data
        send_message($response); //notify all users about new connection

        //make room for new socket
        $found_socket = array_search($socket, $changed);
        unset($changed[$found_socket]);
    }

    //loop through all connected sockets
    foreach ($changed as $changed_socket) { 

        //check for any incomming data
        while(socket_recv($changed_socket, $buf, 1024, 0) >= 1)
        {
            $received_text = unmask($buf); //unmask data
            $tst_msg = json_decode($received_text); //json decode 
            $user_name = $tst_msg->name; //sender name
            $user_message = $tst_msg->message; //message text
            $user_color = $tst_msg->color; //color

            //prepare data to be sent to client
            $response_text = mask(json_encode(array('type'=>'usermsg', 'name'=>$user_name, 'message'=>$user_message, 'color'=>$user_color)));
            send_message($response_text); //send data
            break 2; //exist this loop
        }

        $buf = @socket_read($changed_socket, 1024, PHP_NORMAL_READ);
        if ($buf === false) { // check disconnected client
            // remove client for $clients array
            $found_socket = array_search($changed_socket, $clients);
            socket_getpeername($changed_socket, $ip);
            unset($clients[$found_socket]);

            //notify all users about disconnected connection
            $response = mask(json_encode(array('type'=>'system', 'message'=>$ip.' disconnected')));
            send_message($response);
        }
    }
}
// close the listening socket
socket_close($sock);

function send_message($msg)
{
    global $clients;
    foreach($clients as $changed_socket)
    {
        @socket_write($changed_socket,$msg,strlen($msg));
    }
    return true;
}


//Unmask incoming framed message
function unmask($text) {
    $length = ord($text[1]) & 127;
    if($length == 126) {
        $masks = substr($text, 4, 4);
        $data = substr($text, 8);
    }
    elseif($length == 127) {
        $masks = substr($text, 10, 4);
        $data = substr($text, 14);
    }
    else {
        $masks = substr($text, 2, 4);
        $data = substr($text, 6);
    }
    $text = "";
    for ($i = 0; $i < strlen($data); ++$i) {
        $text .= $data[$i] ^ $masks[$i%4];
    }
    return $text;
}

//Encode message for transfer to client.
function mask($text)
{
    $b1 = 0x80 | (0x1 & 0x0f);
    $length = strlen($text);

    if($length <= 125)
        $header = pack('CC', $b1, $length);
    elseif($length > 125 && $length < 65536)
        $header = pack('CCn', $b1, 126, $length);
    elseif($length >= 65536)
        $header = pack('CCNN', $b1, 127, $length);
    return $header.$text;
}

//handshake new client.
function perform_handshaking($receved_header,$client_conn, $host, $port)
{
    $headers = array();
    $lines = preg_split("/\r\n/", $receved_header);
    foreach($lines as $line)
    {
        $line = chop($line);
        if(preg_match('/\A(\S+): (.*)\z/', $line, $matches))
        {
            $headers[$matches[1]] = $matches[2];
        }
    }

    $secKey = $headers['Sec-WebSocket-Key'];
    $secAccept = base64_encode(pack('H*', sha1($secKey . '258EAFA5-E914-47DA-95CA-C5AB0DC85B11')));
    //hand shaking header
    $upgrade  = "HTTP/1.1 101 Web Socket Protocol Handshake\r\n" .
    "Upgrade: websocket\r\n" .
    "Connection: Upgrade\r\n" .
    "WebSocket-Origin: $host\r\n" .
    "WebSocket-Location: ws://$host:$port/demo/shout.php\r\n".
    "Sec-WebSocket-Accept:$secAccept\r\n\r\n";
    socket_write($client_conn,$upgrade,strlen($upgrade));
}

In order to start the websocket server it's needed to run a console command like this: php -q myserver.php

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