I cant seem to get a simple TCP connection going between a java server application and Android (I have tried both the emulator and the Android Dev Phone 2). I am getting this error on the Emulator "The application Data Receive (process com.mdog.datareceive) has stopped unexpectedly. Please try again."
Forgive me but I am very new to android. So I don't know how to debug it... but I am not trying anything too complex. Eventually I want to try and "consume" the bytes I am receiving in the application. and have the TCP run in the background... but for now simply getting the phone and computer to communicate would be great.
If you can help me that would be awesome.
Code for Android side:
public class Receive extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView tv = new TextView(this);
Socket connectionSocket = null;
byte[] inputHolderByteArray = new byte[5*1024];
/* Connect to Server */
try {
connectionSocket = new Socket("192.168.0.104", 11313);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
/* Send an s to server to start transmission */
try {
PrintWriter out = new PrintWriter(connectionSocket.getOutputStream(), true);
out.print('s');
out.flush();
} catch (IOException e1) {
e1.printStackTrace();
}
/* read server transmission */
try {
connectionSocket.getInputStream().read(inputHolderByteArray);
} catch (IOException e) {
e.printStackTrace();
}
tv.setText("done");
setContentView(tv);
}
}
Each instance of the emulator runs behind a virtual router/firewall service that isolates it from your development machine's network interfaces and settings and from the internet.
The virtual router for each instance manages the 10.0.2/24 network address space — all addresses managed by the router are in the form of 10.0.2., where is a number. Addresses within this space are pre-allocated by the emulator/router.
You have to refer to the development machine with address as: 10.0.2.2 instead of 192.168.0.104 in your case. If you want to refer to another machine in your LAN, then you can Use Network Redirections
http://developer.android.com/guide/developing/tools/emulator.html#emulatornetworking
While superfell is correct that the full stack trace would help diagnose this, based on your code the/a likely problem is that you are breaking up every statement into it separate try/catch blocks. This probably isn't your core issue(my guess is you have a networking issue), but it is what is causing the system to crash.
Typically in Java, statements that are reliant on each other which can throw Exceptions are put in the same try/catch statement. What is most likely happening for you is that the code enters your first try catch block where you try to define a new socket. This fails throwing an exception like 'UnknownHostException'. connectionSocket remains null but the code enters the catch for UnknownHostException. You print the stack trace, but the program doesn't exit. Your code continues on to the following try/catch block where you call
PrintWriter out = new PrintWriter(connectionSocket.getOutputStream(), true);
This causes a NullPointerException. This is a RuntimeException which is not checked and, because it is unchecked, you are not forced to catch it in a catch statement. The exception now causes your VM to crash and causes the error screen you have reported.
So, even though getting the logcat stacktrace will tell us more about your issue, the code you have constructed should be condensed into a single try/catch statement since all code is dependent on the first try/catch completing without error.
Edit:
Try constructing your application like this
public class Receive extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView tv = new TextView(this);
Socket connectionSocket = null;
byte[] inputHolderByteArray = new byte[5*1024];
/* Connect to Server */
try {
connectionSocket = new Socket("192.168.0.104", 11313);
PrintWriter out = new PrintWriter(connectionSocket.getOutputStream(), true);
out.print('s');
out.flush();
connectionSocket.getInputStream().read(inputHolderByteArray);
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
tv.setText("done");
setContentView(tv);
}
}
When we say 'get the stacktrace', this means you need to connect to the emulator or device using the android debug bridge (adb) and a program called logcat. If you only have the emulator and no phone connected to your pc, try running the following:
adb logcat *:D
This will output the log information to the terminal. Leave this window open and run your application. You should see a stack trace get printed. Please take the time to get to know logcat and adb.
Related
I m trying to create a simple test application that connect via Socket to my computer (in localhost).But it thows some exception and I can't figure out how to solve it. NOTE: I m running the apk in my phone (not in an emulator)
Java Server Code
public class Main {
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
Thread t = new Thread(){
#Override
public void run(){
System.out.println("Server is running and listening ... ");
try{
ServerSocket ss = new ServerSocket(7000);
while(true){
Socket s = ss.accept();
System.out.println("Connesso");
DataInputStream dis = new DataInputStream(s.getInputStream());
System.out.println("Received from Client: "+ dis.readUTF());
dis.close();
s.close();
}
}catch(IOException e){
e.printStackTrace();
}
}
};
t.start();
}
}
And this is the
Andorid Client Code:
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
Button sendBTN;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
sendBTN=(Button)findViewById(R.id.button);
sendBTN.setOnClickListener(this);
}
#Override
public void onClick(View v) {
Thread t = new Thread(){
#Override
public void run(){
try {
System.out.println("Starting Connection");
Socket s = new Socket("127.0.0.1", 7000);
System.out.println("Connection DONE");
DataOutputStream dos = new DataOutputStream(s.getOutputStream());
dos.writeUTF("Let's Test The Socket");
dos.flush();
dos.close();
s.close();
System.out.println("Closing socket");
} catch (UnknownHostException e){
System.out.println("There was an Unknown Erorr:");
e.printStackTrace();
} catch (IOException e) {
System.out.println("There was an IOException:");
e.printStackTrace();
}
}
};
t.start();
Toast.makeText(this, "Messagge Sent...", Toast.LENGTH_SHORT).show();
}
}
What I get it this error:
I also tried some other ports like 1432 or 8000 or 8080 but the result is the same
Then I tried to change the IP from 127.0.0.1 to my own PC ip.. and what I get is this error..
EDIT:
I tried to run the app inside an Emulator using 10.0.2.2 as IP and everything woks fine.. I also tried to use my Private Ip in another JAVA Client program and it works fine.. So the problem is just the connection beetween my real phone and my PC (even if they are in the same network)
Make sure the IP when set to use your local machine from the emulator is 10.0.2.2
When you are using your phone and your PC:
If you are on the same network, make sure you're using the appropriate IP for your PC on your network as the server connection host. I usually set my physical machines to static IPs on my network (through my router) so I don't have to constantly look at what they are, but this is by no means a requirement.
If you are using your phone off of your home network, you will have to use the IP your ISP gives to connect, and make sure that the port is forwarded appropriately in your router if you have one set up.
In either case, you'll need to make sure the firewall is allowing incoming connections on the port you are specifying.
Ok I found the solution.
Then I deleted the exception I ve made in my firewall for port 7000 and I created a new exception which allow the connection using port 3000 and now it works fine.
If you're trying to connect the localhost listening server via Android Virtual Device, you must first check whether the "mobile data" in the AVD is in "On" state, since it doesn't work if it is in "Off" state, well I don't know the exact reason but it works like that.
I'm trying to write a String to my webpage using Java in Android Studio by reusing some piece of codes of one Java Eclipse project which works well on my PC.
However, the String just cannot be written to the web page using my Android phone.
public void upload(String FTPaddress, String message){
try {
URL url = new URL(FTPaddress); // my server address
URLConnection urlc = url.openConnection();
OutputStream os = (OutputStream) urlc.getOutputStream(); // To upload
OutputStream buffer = new BufferedOutputStream(os);
buffer.write(message.getBytes());
buffer.close();
os.close();
} catch (FileNotFoundException e) {
// print in log
} catch (IOException e) {
// print in log
}
}
Please note that the function is executed, the mobile phone is connected to the internet, thus I am running it on another thread using asyncTask, and there is no exceptions
So can anyone tell me why it worked on my laptop but not for my mobile phone?
I am looking to get/read the Data I passed after I connected a couple of Android Devices, so far I pair, connect and transmit the information between them, but not sure how to implement the reading part, here I am not sure if I should use createRfcommSocketToServiceRecord or listenUsingRfcommWithServiceRecord to create the reading socket for this purpose.
I have two screens, one where the user push a button and transmit the info and the other where the receiver press another button and read the data, I wonder if the sync is incorrect and after I push the "send" button and then the "read" button the connection is unavailable or if this implementation is just not recomendable all together.
These are my two attempts:
Attempt 1:
//Executed after the user press the read data button
private void connectToServerSocket(BluetoothDevice device, UUID uuid) {
try{
BluetoothServerSocket serverSocket = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(device.getName(),uuid);
//Here is where I get the error:
//io to Server Socket JSR82 Connection is not created, failed or aborted
BluetoothSocket clientSocket = serverSocket.accept();
// Start listening for messages.
StringBuilder incoming = new StringBuilder();
listenForMessages(clientSocket, incoming);
// Add a reference to the socket used to send messages.
transferSocket = clientSocket;
} catch (IOException ioe) {
this.printToast("Excep io toServerSocket:" + ioe.getMessage());
} catch (Exception e) {
this.printToast("Excep toServerSocket:" + e.getMessage());
}
}
Attempt 2:
private void connectToServerSocket(BluetoothDevice device, UUID uuid) {
try{
BluetoothServerSocket clientSocket = device.createRfcommSocketToServiceRecord(uuid);
//clientSocket without method and invoke is not working either
Method m = device.getClass().getMethod("createRfcommSocket", new Class[] {int.class});
clientSocket = (BluetoothSocket) m.invoke(device, 1);
//Here is where I get the error:
//io to Server Socket JSR82 Connection is not created, failed or aborted
clientSocket.connect();
// Start listening for messages.
StringBuilder incoming = new StringBuilder();
listenForMessages(clientSocket, incoming);
// Add a reference to the socket used to send messages.
transferSocket = clientSocket;
} catch (IOException ioe) {
this.printToast("Excep io toServerSocket:" + ioe.getMessage());
} catch (Exception e) {
this.printToast("Excep toServerSocket:" + e.getMessage());
}
}
On serverSocket.accept() or clientSocket.connect() I get the exception:
Connection is not created, failed or aborted
I would appreciate if anyone could guide me towards getting the data reading part working. Thanks.
Take a look at Android's BluetoothChat example included with the Android SDK. I think it does exactly what you want.
$ANDROID_SDK/samples/android-19/legacy/BluetoothChat/src/com/example/android/BluetoothChat
Read the managing the connection part.
Its clearly written in the documentation how to exchange (read/write) info between devices through Bluetooth. http://developer.android.com/guide/topics/connectivity/bluetooth.html
I have a working Java client/server program which is very straightforward and basic. This works fine. However, I am now trying to write an Android client, and I have been unable to connect to the server from my android client. I am using almost identical code for the android networking code as I use for the normal client. My android code is simple, all it does is starts this thread from onCreate:
private int serverPort = 8889;
private String serverIP = "192.168.5.230";
private Socket socket = null;
private Thread clientThread = new Thread("ClientThread") {
#Override
public void run() {
try {
socket = new Socket();
socket.connect(new InetSocketAddress(serverIP, serverPort), 1000);
DataInputStream din = new DataInputStream( socket.getInputStream());
DataOutputStream dout = new DataOutputStream(socket.getOutputStream());
while (true) {
String message = din.readUTF();
setPicture("picture1");
}
} catch (UnknownHostException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
The port is the correct port my server is running on, as is the ip address (which I got from ifconfig since I know you cannot use localhost). When I run my normal pc client with the same port and IP address, the connection goes through. But when I run this code on my android device, the socket timesout when I try to connect.
Does anyone have any suggestions for where I am going wrong?
Double check that you added the permission requirement in the manifest file:
<uses-permission android:name="android.permission.INTERNET" />
But, possibly more importantly, 192.168.x.x is a local or non-routable network so you need to be on the same network, or one that knows how to reach the 192.168.5.230 address. You say that it doesn't work when you try it on your device -- are you running on local wifi when you run or are you on your mobile network? If you're on mobile, try it from wifi.
I am working to add Bluetooth capabilities to my app and ultimately the device that I want to use is a headset/earpiece. I have begun assembling the code and I partial functionality with it. When I got to the code for setting up a bluetooth connection by server, I got errors when adding the code. I have tried solving the problems through the hover over the error and autocorrect but every time I fix one problem a different on arises. This leads me to believe that I am missing something that autocorrect doesn't know about. I need some help fixing the errors. Useful suggestions for setting a bluetooth codin for the first time would also be appreciated. Errors are surrounded with ||#| xxx |||. Error 1:cannot be resolved. Error 2:cannot be resolved to a variable. Error 3:undefined for the type AcceptSocket.
import java.io.IOException;
import android.bluetooth.BluetoothServerSocket;
import android.bluetooth.BluetoothSocket;
public class AcceptSocket extends Thread {
private static final String MY_UUID = null;
BluetoothServerSocket mmServerSocket;
public void AcceptThread() {
// Use a temporary object that is later asssigned to mmServerSocket,
// because mmServerSocket is final
BluetoothServerSocket tmp = null;
try {
// MY_UUID is the app's UUID string, also used by the client code
tmp = ||1|mBluetoothAdapter|||.listenUsingRfcommWithServiceRecord(||2|NAME|||,
MY_UUID);
} catch (IOException e) {
}
mmServerSocket = tmp;
}
public void run() {
BluetoothSocket socket = null;
// Keep listening until exception occurs or a socket is returned
while (true) {
try {
socket = mmServerSocket.accept();
} catch (IOException e) {
break;
}
// If a connection was accepted
if (socket != null) {
// Do work to manage the connection (in a separate thread)
||3|manageConnectedSocket|||(socket);
mmServerSocket.close();
break;
}
}
}
/** Will cancel the listening socket, and cause the thread to finish */
public void cancel() {
try {
mmServerSocket.close();
} catch (IOException e) {
}
}
}
Error 1,2: There is no constant called NAME anywhere in the class.
Error 3: There is no method called manageConnectedSocket() in the class.
You can't just copy and paste something from the developer's page and expect it to work. It leads you in the correct direction and you have to fill in the missing pieces.