Android App Connecting to Node.js server using Socket.io

Question

I'm having trouble getting my Android app to connect to a socket.io chat server. I'm using socket.io-java-client created by Gottox which can be found here: https://github.com/Gottox/socket.io-java-client

The server runs locally over port 7000. I'm using the android emulator, so I'm using 10.0.2.2:7000 to access the server.

Any help would be appreciated, I don't have much experience at all with SSL. If I find a working solution I'll also post it.

Node.js Server

var express = require('express'); var app = express(); var server = require('http').createServer(app).listen(7000); var io = require('socket.io').listen(server); io.sockets.on('connection', function(client){     client.on('message', function(err, msg){         client.broadcast.emit('message', msg);     });  }); 

package.json

{   "name": "simplechat",   "version": "0.0.1",   "main": "app.js",   "dependencies": {     "express" : "~4.0.0",     "socket.io" : "~0.9.13"   } } 

Android: SendMessageActivity

public class SendMessageActivity extends Activity {      private static final String SERVER_ADDRESS = "https://10.0.2.2:7000";      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_send_message);          System.out.println("Sever: " + SERVER_ADDRESS);          try {             SocketIO socket = new SocketIO(new URL(SERVER_ADDRESS), new IOCallback() {                 @Override                 public void onDisconnect() {                     System.out.println("disconnected");                 }                  @Override                 public void onConnect() {                     System.out.println("connected");                 }                  @Override                 public void onMessage(String s, IOAcknowledge ioAcknowledge) {                 }                  @Override                 public void onMessage(JSONObject jsonObject, IOAcknowledge ioAcknowledge) {                 }                  @Override                 public void on(String event, IOAcknowledge ioAcknowledge, Object... objects) {                 }                  @Override                 public void onError(SocketIOException e) {                     e.printStackTrace();                 }             });          } catch (MalformedURLException ex) {             ex.printStackTrace();         }     } 

Android Permissions

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

Error Code

08-09 16:07:28.224    8411-8441/com.example.puma.chatexample W/System.err﹕ io.socket.SocketIOException: Error while handshaking 08-09 16:07:28.225    8411-8441/com.example.puma.chatexample W/System.err﹕ at io.socket.IOConnection.handshake(IOConnection.java:322) 08-09 16:07:28.225    8411-8441/com.example.puma.chatexample W/System.err﹕ at io.socket.IOConnection.access$600(IOConnection.java:39) 08-09 16:07:28.225    8411-8441/com.example.puma.chatexample W/System.err﹕ at io.socket.IOConnection$ConnectThread.run(IOConnection.java:199) 08-09 16:07:28.226    8411-8441/com.example.puma.chatexample W/System.err﹕ Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'javax.net.ssl.SSLSocketFactory javax.net.ssl.SSLContext.getSocketFactory()' on a null object reference 08-09 16:07:28.226    8411-8441/com.example.puma.chatexample W/System.err﹕ at io.socket.IOConnection.handshake(IOConnection.java:302) 08-09 16:07:28.227    8411-8441/com.example.puma.chatexample W/System.err﹕ ... 2 more 

Answer 1

I actually solved the problem. I used my PC's local IP http://192.168.0.xxx:7000 and the app was able to connect to the chat server from the emulator. I don't know why this works, but it might help out someone in the future :)

Update:

This is how I ended up structuring the project. I created a singleton class to handle socket connections Android side (you could also do it as a service). When receiving a message, the singleton class broadcasts an intent to the rest of the app. The intent is then picked up by a broadcast receiver in the relevant activity.

Android Side (singleton):

public class SocketSingleton {      private static SocketSingleton instance;     private static final String SERVER_ADDRESS = "http://1.2.3.4:1234";     private SocketIO socket;     private Context context;      public static SocketSingleton get(Context context){         if(instance == null){             instance = getSync(context);         }         instance.context = context;         return instance;     }      public static synchronized SocketSingleton getSync(Context context){         if (instance == null) {             instance = new SocketSingleton(context);         }         return instance;     }      public SocketIO getSocket(){         return this.socket;     }      private SocketSingleton(Context context){         this.context = context;         this.socket = getChatServerSocket();         this.friends = new ArrayList<Friend>();     }      private SocketIO getChatServerSocket(){         try {             SocketIO socket = new SocketIO(new URL(SERVER_ADDRESS), new IOCallback() {                 @Override                 public void onDisconnect() {                     System.out.println("disconnected");                 }                  @Override                 public void onConnect() {                     System.out.println("connected");                 }                  @Override                 public void on(String event, IOAcknowledge ioAcknowledge, Object... objects) {                     if (event.equals("chatMessage")) {                         JSONObject json = (JSONObject) objects[0];                         ChatMessage chatMessage = new ChatMessage(json);                          Intent intent = new Intent();                         intent.setAction("newChatMessage");                         intent.putExtra("chatMessage", chatMessage);                         context.sendBroadcast(intent);                     }                 }                 @Override                 public void onError(SocketIOException e) {                     e.printStackTrace();                 }             });             return socket;         } catch (MalformedURLException ex) {             ex.printStackTrace();         }         return null;     } } 

Android Side (activity):

public class ChatActivity extends Activity {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_chat);     IntentFilter newChatMessageFilter = new IntentFilter("newChatMessage");     this.registerReceiver(new MessageReceiver(), newChatMessageFilter);      ...      public class MessageReceiver extends BroadcastReceiver {         @Override         public void onReceive(Context context, Intent intent){             final ChatMessage chatMessage =(ChatMessage) intent.getExtras().get("chatMessage");             runOnUiThread(new Runnable() {                 @Override                 public void run() {                     mAdapter.add(chatMessage);                     mAdapter.notifyDataSetChanged();                 }             });         }     } }  

Server Side:

var express = require('express'); var app = express(); var server = require('http').createServer(app).listen(1234); var io = require('socket.io').listen(server);  io.sockets.on('connection', function(client){      console.log("client connected: " + client.id);      client.on("sendTo", function(chatMessage){         console.log("Message From: " + chatMessage.fromName);         console.log("Message To: " + chatMessage.toName);           io.sockets.socket(chatMessage.toClientID).emit("chatMessage", {"fromName" : chatMessage.fromName,                                                                     "toName" : chatMessage.toName,                                                                     "toClientID" : chatMessage.toClientID,                                                                     "msg" : chatMessage.msg});      }); }); 

Answer 2

I know this not really answers to the OP's posts, but for those who may be interested, this is a tutorial I made to make communicate your Android with a Node.js server -without any additional library- :

https://causeyourestuck.io/2016/04/27/node-js-android-tcpip/

This is a foretaste of how it looks like at the end:

Client socket = new Client("192.168.0.8", 1234); socket.setOnEventOccurred(new Client.OnEventOccurred() {     @Override     public void onMessage(String message) {     }      @Override     public void onConnected(Socket socket) {         socket.send("Hello World!");         socket.disconnect();     }      @Override     public void onDisconnected(Socket socket, String message) {     } });  socket.connect();