I have two Android devices which I want to connect, using Bluetooth, and transfer data over an RFCOMM channel. I only one one device to receive data, while the other device sends it...
Using this code, I am able to connect to the other device and begin listening to an RFCOMM channel:
Method m = device.getClass().getMethod("createRfcommSocket", new Class[] { int.class });
socket = (BluetoothSocket) m.invoke(device, 2);
socket.connect();
class BasicThread implements Runnable{
public void run() {
try {
InputStream stream = socket.getInputStream();
BufferedReader r = new BufferedReader(new InputStreamReader(stream));
while (true){
Log.d("myapp", "now listening...");
latestLine = r.readLine();
Log.d("myapp", latestLine);
}
} catch (IOException e) {
}
}
}
new Thread(new BasicThread()).run();
Using the other device, I have implemented a listening socket like this:
Method m = blue.getClass().getMethod("listenUsingRfcommOn", new Class[] { int.class });
BluetoothServerSocket socket = (BluetoothServerSocket) m.invoke(blue, 2);
BluetoothSocket sock = socket.accept();
Log.d("myapp", "Connected...\n\n\n\n\n\n\n\n");
OutputStream s = sock.getOutputStream();
final PrintWriter out = new PrintWriter(s);
They both connect on RFCOMM channel 2, and both SEE eachother, however, the second device always remains blocked at the BluetoothSocket sock = socket.accept();
Any help?
OK, I am newbie, but I can try to help. So here is my experience, I managed to connect two devices using reflection. My Android phone is receiving data using method listenUsingInsecureRfcommOn, while other devices are masters in communication and send the data over BT SPP. I had a problem with this method since it makes no visible SDP record, so I could not detect it with other devices. Because of that, I made small sniffer using Bluecove and Java SE that tries to connect to every port in given range. Here's the code:
package application.test;
import static java.lang.System.out;
import java.io.InputStream;
import java.io.PrintStream;
import java.text.SimpleDateFormat;
import javax.microedition.io.Connector;
import javax.microedition.io.StreamConnection;
public class RfCommClient {
public static void main(String args[]) {
try {
Thread.sleep(1000);
} catch (InterruptedException e1) {
e1.printStackTrace();
}
String add = "btspp://8C71F894A36D:";
String par = ";authenticate=false;encrypt=false;master=true";
String url = null;
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd;HH-mm-ss-SSS");
for (int i = 1; i < 15; ++i) {
try {
url = add + i + par;
out.format("Time: %s, port = %d\n", sdf.format(System.currentTimeMillis()), i);
StreamConnection conn = (StreamConnection) Connector.open(url);
PrintStream ops = new PrintStream(conn.openOutputStream());
ops.println("Hi there...");
// response
Thread.sleep(1000);
InputStream is = conn.openInputStream();
byte[] resp = new byte[5];
int r = is.read(resp);
out.println("r = " + r + ", response = " + new String(resp, "US-ASCII"));
Thread.sleep(10 * 1000);
conn.close();
} catch (Exception e) {
out.println("Exception occured, time = " + sdf.format(System.currentTimeMillis()) + ", i = " + i);
//e.printStackTrace();
}
}
}
}
What I've learned it that some ports are taken, and that some ports can not be uses (as documentation says, e.g. port 0). For example, port 2 I believe was taken, because when I send some data to it I receive 5 chars back beginning with ERR :).
While, on the other hand, my thread is still waiting?! :)
That leads us to another thing I noticed, ports (or channels) are not always mapped to desired number. For example, to me often happened that I want to send something on port 15, but on Android, thread waiting on port 9 received the data :)
So I suggest, check which port is really allocated!
You can achieve that using the code I posted.
And another thing, here is a link to channelPicker function, which selects channel when ordinary API is used, if I am not mistaken, inside some constants should represent reserved channels.
I just noticed something, my code for registering port is slightly different, here is how I do it:
Method m = cba.getDeclaredMethod("listenUsingInsecureRfcommOn", int.class);
ss = (BluetoothServerSocket) m.invoke(BluetoothAdapter.getDefaultAdapter(), port);
Anyway, I know that this is probably too late, but, maybe someone in future has similar question.
Related
I get bit problem, The problem is as follows:
At server socket, server receive data type as byte array:
this.receiveStream = new DataInputStream(this.clientSocket.getInputStream());
byte[] receiveBuffer = new byte[bufferSize];
while (this.receiveStream.read(receiveBuffer, 0, receiveBuffer.length) > -1) {
String dataReceive = new String(receiveBuffer, StandardCharsets.UTF_8).trim();
}
If client send text message in one thread then server run well, but if client run >=2 thread concurrent to send text message then at server, the message were mixed, it mean clientThead1 send "ABC", clientThead2 send "XYZ" => server receive "AXBC" OR "AXYZ",... => It is not expected message.
How to solve this problem???
P/S: I have tested with server receive message as text, it work well:
while (true) {
String dataReceive = this.receiveStream.readUTF().trim();
}
But i can not use it, because server serve muti platform client, so i want to server use byte array to receive data
Thanks all,
UPDATE:
I can not post full code because it is very long character
This is link all code Client + Server:https://www.mediafire.com/folder/j4d041uqfowt6/SocketApp
Do you use TCP or UDP? It is important, the sockets do not hide the difference.
For TCP,
the client threads must not reuse the same connection.
Each client thread must open its own connection, as if it were applications on different devices.
The server must start a new thread each time it listening socket receives a job. That thread will use its own connection; threads servicing different clients are independent as if it were applications on different devices.
I think you see the logic: one client thread <--> one service thread.
(I think you know that a listening socket does not receive data, it creates a data socket).
For UDP, on the server side you have to distinguish the clients yourself.
It would not be possible if you were sending single bytes, but packets are not single bytes, UDP packets include auxiliary information. You have the sender's IP and port, so you can distinguish the clients if they are not two threads using the same port on the same IP.
Use a child thread to read data from socket and main thread to accept request and hand over to child..
Server
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;
public class Server extends Thread {
public Server(String ip, int port) {
try {
ServerSocket ser = new ServerSocket(port);
System.out.println("Listening....");
while (true) {
Socket soc = ser.accept();
new Child(soc).start();
System.out.println("Child Started...");
}
} catch (IOException e) {
}
}
private class Child extends Thread {
Socket cSoc;
public Child(Socket soc) {
this.cSoc = soc;
}
#Override
public void run() {
try {
String data = "";
InputStream in = cSoc.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(in));
int ch = 0, cnt = 0;
byte[] buffer = new byte[1024];
int length = Integer.parseInt(br.readLine());
System.out.println("Message Length = " + length);
while ((ch = in.read(buffer)) != -1) {
data += new String(buffer);
cnt += ch;
if (cnt >= length) {
break;
}
}
System.out.println("Message = " + data);
} catch (IOException ex) {
}
}
}
public static void main(String[] args) {
new Server("localhost", 1234).start();
}
}
Client
import java.io.OutputStream;
import java.io.PrintStream;
import java.net.Socket;
public class Client {
public static void main(String[] args) {
try {
Socket s = new Socket("localhost", 1234);
OutputStream o = s.getOutputStream();
PrintStream ps = new PrintStream(o);
String data = "your data";
ps.println(data.length());
Thread.sleep(100);
o.write(data.getBytes());
ps.close();
o.close();
} catch (Exception e) {
}
}
}
It's just a sample implementation you can wrap the concept.
I'm writing an Android app using sockets for communication. In a class called sever I accept clients (android devices) and open sockets for them.
Server side:
public void run() {
while (!Thread.currentThread().isInterrupted()) {
try {
Socket socket = serverSocket.accept();
Client clientThread = new Client(socket);
System.out.println("New client: " + clientThread.getName());
new Thread(clientThread).start();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
After a succesful connection the user may create a group, which is like a room for number of clients to connect and play together.
The group creation is done here:
Server side:
Client:
private void client_create() {
this.mGroup = new Group();
mGroup.joinPlayer(this);
System.out.println("New group for: " + name);
}
Group:
public Group(int nClients){
// Clients in this group
this.clients = new ArrayList<Client>();
}
public void joinPlayer(Client player){
clients.add(player);
}
Client Side:
Connection handling:
try {
socket = new Socket(hostName, portNumber);
out = new PrintWriter(new BufferedWriter(
new OutputStreamWriter(socket.getOutputStream())), true);
in = new BufferedReader(new InputStreamReader(
socket.getInputStream()));
Listener listener = new Listener();
new Thread(listener).start();
} catch (IOException e) {
e.printStackTrace();
}
I ran this programm on 2 android devices and on my localhost as the server. After the connection was made, I tried creating 2 independent different groups. While debugging it all seems legit until I reached to a point where I lost it due to the 2 different running threads.
The odd thing that happened is that after the first group was created with the first client (clients contains the first device client object), and then the second group with the second player (clients contains the second device client object), the first group clients array contains the second client object (from the second device).
Have you got any thoughts on that? Did I do something wrong?
Figured it out.
Clients was mistakly defined as static, so I guess when accessing to the clients array of the static object it received the last one who was created.
This is a continuation of this question because it my orginal question was answered, but it did not solve the bug.
Question:
How do I fix the code hanging on this line inStream.readline()
My Intent:
This is in a thread that will loop through checking if there is an outMessage, if there is, it will send the message.
Next it will check it if there is anything in the in-stream, if there is, it will send it to the handler in my main activity.
Lastly, it will sleep for 1 second, then check again.
This should allow me to read/write multiple times without needing to close and open the socket.
Problem:
It is reading and writing better, but still not working properly
What is happening now:
If outMessage is initialized with a value, upon connection with the server, the socket:
writes and flushes the value (server receives & responds)
updates value of outMessage (to null or to "x" depending on how i have it hard-coded)
reads and shows the response message from the server
re-enters for the next loop
IF i set outMessage to null, it skips over that if statements correctly then hangs; otherwise, if i set outMessage to a string (lets say "x"), it goes through the whole if statement, then hangs.
The code it hangs on is either of the inStream.readline() calls (I currently have one commented out).
Additional info:
- once connected, I can type in the "send" box, submit (updates the outMessage value), then disconnect. Upon re-connecting, it will read the value and do the sequence again until it get stuck on that same line.
Changes since the referenced question:
- Made outMessage and connectionStatus both 'volatile'
- added end-of-line delimiters in neccesary places.
Code:
public void run() {
while (connectionStatus != TCP_SOCKET_STATUS_CONNECTED) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
while (connectionStatus == TCP_SOCKET_STATUS_CONNECTED) {
try {
if (outMessage != null){
OutStream.writeBytes(outMessage + "\n");
OutStream.flush();
sendMessageToAllUI(0, MAINACTIVITY_SET_TEXT_STATE, "appendText" , "OUT TO SERVER: " + outMessage);
outMessage = "x";
}
Thread.sleep(100);
// if (InStream.readLine().length() > 0) {
String modifiedSentence = InStream.readLine();
sendMessageToAllUI(0, MAINACTIVITY_SET_TEXT_STATE, "appendText" , "IN FROM SERVER: " + modifiedSentence);
// }
Thread.sleep(1000);
} catch (IOException e) {
connectionLost();
break;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
The thread that makes the socket:
public void run() {
setName("AttemptConnectionThread");
connectionStatus = TCP_SOCKET_STATUS_CONNECTING;
try {
SocketAddress sockaddr = new InetSocketAddress(serverIP, port);
tempSocketClient = new Socket(); // Create an unbound socket
// This method will block no more than timeoutMs. If the timeout occurs, SocketTimeoutException is thrown.
tempSocketClient.connect(sockaddr, timeoutMs);
OutStream = new DataOutputStream(tempSocketClient.getOutputStream());
InStream = new BufferedReader(new InputStreamReader(tempSocketClient.getInputStream()));
socketClient = tempSocketClient;
socketClient.setTcpNoDelay(true);
connected();
} catch (UnknownHostException e) {
connectionFailed();
} catch (SocketTimeoutException e) {
connectionFailed();
} catch (IOException e) {
// Close the socket
try {
tempSocketClient.close();
} catch (IOException e2) {
}
connectionFailed();
return;
}
}
Server:
public static void main(String[] args) throws IOException {
String clientSentence;
String capitalizedSentence;
try {
ServerSocket welcomeSocket = new ServerSocket(8888);
SERVERIP = getLocalIpAddress();
System.out.println("Connected and waiting for client input!\n Listening on IP: " + SERVERIP +"\n\n");
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
while(true)
{
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
clientSentence = inFromClient.readLine();
System.out.println("clientSentance == " + clientSentence);
String ip = connectionSocket.getInetAddress().toString().substring(1);
if(clientSentence != null)
{
System.out.println("In from client ("+ip+")("+ System.currentTimeMillis() +"): "+clientSentence);
capitalizedSentence = clientSentence.toUpperCase() + '\n';
outToClient.writeBytes(capitalizedSentence + '\n');
System.out.println("Out to client ("+ip+"): "+capitalizedSentence);
}
}
} catch (IOException e) {
//if server is already running, it will not open new port but instead re-print the open ports information
SERVERIP = getLocalIpAddress();
System.out.println("Connected and waiting for client input!\n");
System.out.println("Listening on IP: " + SERVERIP +"\n\n");
}
}
Thanks in advance!
Edits:
added the server code after updating
I tried messing around with setting the SoTimout for the socket but took that back out
Your server is specifically designed to receive exactly one line from a client and send exactly one line back. Look at the code:
while (true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient = new BufferedReader(
new InputStreamReader(connectionSocket.getInputStream()));
DataOutputStream outToClient = new DataOutputStream(
connectionSocket.getOutputStream());
clientSentence = inFromClient.readLine();
String ip = connectionSocket.getInetAddress().toString()
.substring(1);
System.out.println("In from client (" + ip + "): "
+ clientSentence);
if (clientSentence != null) {
capitalizedSentence = clientSentence.toUpperCase() + '\n';
System.out.println("Out to client (" + ip + "): "
+ capitalizedSentence);
outToClient.writeBytes(capitalizedSentence + "\n");
}
Notice that inside the loop it accepts a new connection, reads exactly one line, and then writes exactly one line. It doesn't close the connection. It doesn't sanely end the conversation. It just stops reading.
A client that worked with this server would have to connect, send exactly one line, read exactly one line back, and then the client would have to close the connection. Your client doesn't do that. Why? Because you had no idea that's what you had to do. Why? Because you had no design ... no plan.
So that's your specific issue. But please, let me urge you to take a huge step back and totally change your approach. Before you write a single line of code, please actually design and specify a protocol at the byte level. The protocol should say what data is sent, how messages are delimited, who sends when, who closes the connection, and so on.
Otherwise, it's impossible to debug your code. Looking at the server code above, is it correct? Well, who knows. Because it's unclear what it's supposed to do. When you wrote the client, you assumed the server behaved one way. Was that assumption valid? Is the server broken? Who knows, because there's no specification of what the server is supposed to do.
You need to check if there is data available:
if (InStream.available > 0) {
String modifiedSentence = InStream.readLine();
sendMessageToAllUI(0, MAINACTIVITY_SET_TEXT_STATE, "appendText" , "IN FROM SERVER: " + modifiedSentence);
}
But to be honest, even that is not ideal because you have no gurantee that the eond-of-line will have been received. If the server sends a few bytes but never sends the end-of-line then you will still be blocking forever. Production socket code should never rely on readLine but instead read into a buffer and check that buffer for end-of-line (or whatever criteria your protocol needs).
Didn't read closely enough, I thought InStream was an InputStream instance. InputStream has available. InputStreamReader has ready (which in turn calls InputStream.available. As long as you keep a refernce to either of these then you can see if data is available to be read.
Just to make it short. I want to connect to three devices and read the data from all the three at the same time. I know how to connect to one and i can read the data from that But What i want is to connect the other two and read from them.Any suggestions , or other example i can follow.
Here is part of the code which is similar to mine but shorter . This code can connect to one device using the mac. So How to modify this to connect to three devices at the same time and display the data they are sending?
Please help i really need it cause am stuck at this part of my project. Thanks for the help.
private boolean connected = false;
private BluetoothSocket sock;
private InputStream in;
public void test() throws Exception {
if (connected) {
return;
}
BluetoothDevice zee = BluetoothAdapter.getDefaultAdapter().
getRemoteDevice("00:14:C5:A1:02:67");
Method m = zee.getClass().getMethod("createRfcommSocket",
new Class[] { int.class });
sock = (BluetoothSocket)m.invoke(zee, Integer.valueOf(1));
devicecon.setText("Connecting......");
sock.connect();
devicecon.setText("Connected");
in = sock.getInputStream();
byte[] buffer = new byte[50];
int read = 0;
Log.d("ZeeTest", "++++ Listening...");
try {
while (true) {
read = in.read(buffer);
connected = true;
StringBuilder buf = new StringBuilder();
for (int i = 0; i < read; i++) {
int b = buffer[i] & 0xff;
if (b < 0x10) {
buf.append("0");
}
buf.append(Integer.toHexString(b)).append(" ");
}
Log.d("ZeeTest", "++++ Read "+ read +" bytes: "+ buf.toString());
}
} catch (IOException e) {}
Log.d("ZeeTest", "++++ Done: test()");
All you need to do is create a new thread (I suggest using an instance of AsyncTask for this rather than an actual Thread) for each device and call the connection code snippet
BluetoothDevice zee = BluetoothAdapter.getDefaultAdapter().
getRemoteDevice("00:14:C5:A1:02:67");
Method m = zee.getClass().getMethod("createRfcommSocket",
new Class[] { int.class });
sock = (BluetoothSocket)m.invoke(zee, Integer.valueOf(1));
devicecon.setText("Connecting......");
sock.connect();
from inside that new thread.
I'm designin an application in Android that connects the mobile to a bluetooth device. I can do this, as I open a BluetoothSocket like this:
Method m = device.getClass().getMethod("createRfcommSocket", new Class[] {int.class});
socket = (BluetoothSocket) m.invoke(device, 1);
socket.connect();
Where device is the paired device with the mobile bluetooth desired. The thing is, this external device is a bit special, and it has different times for writing and answering to the mobile, so I need to put some timeouts on my socket for reading and writing, but I've searched a lot and it seems like BluetoothSocket doesn't support this.
Can anybody tell me a different way to admin timeouts on reading and writing to the port on the BluetoothSocket class for Android?
Thank you!
There are many Exceptions a socket or it's streams can throw. The socket.connect() for example can throw a ConnectTimeoutException. Every method in the BluetoothSocket context can through an IOException just take a look at the documentation and you will see which exception you have to catch in order to make your program work properly.
Here is the code for reading and writing code:
Writng code on port:
try
{
// Enviamos los bytes
DataOutputStream dOut = null;
dOut = new DataOutputStream(socket.getOutputStream());
// Send message
dOut.writeBytes(res);
dOut.flush();
}
catch (IOException e)
{
Dialogs.showErrorDialog("Error al recuperar la fecha y hora del dispositivo Nonin.", this);
}
Then, reading from port until response available:
DataInputStream dIn = null;
// We receive the answer
try
{
dIn = new DataInputStream(socket.getInputStream());
}
catch (IOException e)
{
Dialogs.showAlertDialog("An exception occured during bluetooth io stream creation", this);
}
while (true)
{
try
{
String data = dIn.readLine(); // readLine();
byte[] total = EncodingUtils.getBytes(data, "ASCII");
Dialogs.showInfoDialog("Mensaje ok: " + data.toString(), this);
}
catch (IOException e)
{
break;
}
}
The thing is that I think the writing works, as I convert the desired string into bytes, and it works. But then, when I'm waiting for response, it mixes further responses with the desired, and I think this is because timings.
There's no more code in the middle related with sockets. First, I create it. Then, I try to send a byte String. Then I wait until I receive the answer for the byte String that I just sent.
Thank you in advance.