We Keep Coding

How to stream data between server and client

I am using Apache Mina SSHD to communicate with two Android devices. I have server-side code and client-side I'd like to establish a connection and start streaming data (byte array packet) from server to client and client to server until a button pressed to disconnect. How can I do this?
SERVER
I use this link SSHD SERVER stackOverflow
public void startSSHServer() {
int port = 22;
SshServer sshd = SshServer.setUpDefaultServer();
sshd.setPort(port);
sshd.setKeyPairProvider(new SimpleGeneratorHostKeyProvider(
"src/test/resources/hostkey.ser"));
sshd.setSubsystemFactories(Arrays
.<NamedFactory<Command>>asList(new SftpSubsystem.Factory()));
sshd.setCommandFactory(new ScpCommandFactory());
sshd.setShellFactory(new ProcessShellFactory(new String[]{"/system/bin/sh", "-i", "-l"})); // necessary if you want to type commands over ssh
sshd.setPasswordAuthenticator(new PasswordAuthenticator() {
#Override
public boolean authenticate(String u, String p, ServerSession s) {
return ("sftptest".equals(u) && "sftptest".equals(p));
}
});
try {
sshd.start();
} catch (IOException e) {
e.printStackTrace();
}
}
CLIENT
I use this link SSHD CLIENT geeksforgeeks
Thread thread = new Thread(new Runnable() {
#Override
public void run() {
try {
// Connection establishment and authentication
try (ClientSession session = client.connect(username, host, port).verify(10000).getSession()) {
session.addPasswordIdentity(password);
session.auth().verify(50000);
System.out.println("Connection establihed");
// Create a channel to communicate
channel = session.createChannel(Channel.CHANNEL_SHELL);
System.out.println("Starting shell");
ByteArrayOutputStream responseStream = new ByteArrayOutputStream();
channel.setOut(responseStream);
// Open channel
channel.open().verify(5, TimeUnit.SECONDS);
try (OutputStream pipedIn = channel.getInvertedIn()) {
pipedIn.write(command.getBytes());
pipedIn.flush();
}
// Close channel
channel.waitFor(EnumSet.of(ClientChannelEvent.CLOSED),
TimeUnit.SECONDS.toMillis(5));
// Output after converting to string type
String responseString = new String(responseStream.toByteArray());
System.out.println(responseString);
shellOutput.setText(responseString);
} catch (IOException e) {
e.printStackTrace();
} finally {
client.stop();
}
} catch (Exception e) {
e.printStackTrace();
}
}
});
thread.start();

How to create a socket that listens a localhost port in Android

Before explain my doubt I want to mension that there're three "actors" in this enviorement:
A desktop program executed in some server
A person who uses this program remotely through a computer
And an Android tablet application that is connected with the computer via USB
When the person clicks on a link bar in this program that he is using remotely there's a shell script that sends a string to the person's computer port(e.g 1100). The requirement is: After recive this string from the desktop send it to the tablet.
So, what is the best way to recive this string from the desktop to the tablet?
Now there's a java daemon that is running in the desktop computer who is listening the 1100 port. This java app is working as a intermidiate between the desktop computer and the tablet, but I think that maybe there's a way to delete this daemon and just using the tablet to recive the computer data creating a socket.

You can also implement Java Sockets in Android. Like wise on Desktop Sockets in Android listens on ports but this will be accessed locally as there is no such way to assign static usable IP to an Android device.
There is another solution which is socket.io
Socket.io is one of the best socket library i have ever used. Implement socket.io on Node.js server and on Android simply connect to Node.js server and you can send same string to all connected users whether it is a Desktop or Android.

private class ServerThread extends Thread {
#Override
public void run() {
try {
serverSocket = new ServerSocket(portNumber);
while (true) {
try {
clientSocket = serverSocket.accept();
} catch (IOException e) {
LOGGER.error("Error on accept!");
}
// new thread for a client
new EchoThread(clientSocket).start();
}
}catch (Exception e) {
e.printStackTrace();
}
finally {
if (serverSocket != null) {
try {
serverSocket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
public class EchoThread extends Thread {
protected Socket clientSocket;
BufferedReader br = null;
public EchoThread(Socket clientSocket) {
this.clientSocket = clientSocket;
}
public void run() {
try {
br = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
} catch (IOException e) {
...
}
isConnected = true;
while (isConnected) {
try {
receivedMessage = br.readLine();
if (!Strings.isNullOrEmpty(receivedMessage)) {
....
}
else {
//sleep 0,1s
//TODO (ver): Thread.sleep(100);
}
} catch (Exception e) {
if (e instanceof IOException) {
}
else if (e instanceof JsonSyntaxException){
}
else {
try {
Thread.sleep(2000);
} catch (InterruptedException inte) {
inte.printStackTrace();
}
}
}
if (//yourmessagecondition){
isConnected = false;
}
}
if (!isConnected){
try {
br.close();
clientSocket.close();
}catch (IOException ioe){
ioe.printStackTrace();
}
}
}
}
Hope this helps, it is working here... You probably find easier/simple examples on the Internet.
PS: If you are using a USB cable to communicate with the computer app, you can use the "adb forward" command, just google for some examples and accept this answer if it helped ;)

Manage all incoming chat messages in java socket programming

I am developing a program that has a chat feature and I am using sockets in it.
In my case, I want to handle each of the client in a different window chat(PLEASE SEE ATTACHED IMAGE).
As of now, when 1 client is connected, there is no problem. But when 2 clients are connected, the first client will be overridden by the 2nd one and he can't receive messages from server not unless I close the connection for the latest client connected(Server still receiving messages from all client although only 1 client can receive from server).
How am I gonna do this? I am using captain casa framework
I want to manage it like what did the image below do.
IMAGE HERE
Here is my code:
Server:
public void mainserver(){
Thread server = new Thread(new Runnable() {
#Override
public void run() {
try {
serverSocket = new ServerSocket(port);
System.out.println("Server Online... \nWaiting for Connections");
} catch (IOException e) {
e.printStackTrace();
}
while (accept){
try {
socket = serverSocket.accept();
System.out.println("New Connection Estasblished!!!");
chatHandler chat = new chatHandler(socket);
chat.start();
} catch (IOException e) {
System.out.println("server not terminate all connections");
System.exit(-1);
}
}
}
});
server.start();
}
public class chatHandler extends Thread{
Socket socket;
public chatHandler(Socket socket){
this.socket = socket;
}
public void run(){
try {
din = new DataInputStream(socket.getInputStream());
dout = new DataOutputStream(socket.getOutputStream());
dout.writeUTF("Hi! Thank you for reaching us! How may I help you!?");
while (!read.equals(".end")){
read = din.readUTF();
if (getServerArea()!=null){
setServerArea(getServerArea()+"\n"+read);
}else {
setServerArea(read);
}
}
System.out.println("end of chat server");
} catch (IOException e) {
e.printStackTrace();
}finally {
System.out.println("Exit");
try {
dout.close();
din.close();
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
public void serverSend(javax.faces.event.ActionEvent event) { // "Send" button
write = getServerField();
try {
dout.writeUTF(write);
dout.flush();
if (getServerArea()!=null){
setServerArea(getServerArea()+"\n"+write);
setServerField("");
}else {
setServerArea(write);
setServerField("");
}
} catch (IOException e) {
e.printStackTrace();
}
System.out.println(write);
}
Client:
public void client(){
Thread client = new Thread(new Runnable() {
#Override
public void run() {
try {
socket = new Socket("localhost",port);
din = new DataInputStream(socket.getInputStream());
dout = new DataOutputStream(socket.getOutputStream());
while (!read.equals("bye")){
read = din.readUTF();
if (getClientArea()!=null){
setClientArea(getClientArea()+"\n"+read);
}else {
setClientArea(read);
}
}
} catch (IOException e) {
e.printStackTrace();
}finally {
try {
din.close();
dout.close();
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
});
client.start();
}
public void clientSend(javax.faces.event.ActionEvent event) {
write = getClientField();
try {
dout.writeUTF(write);
dout.flush();
if (getClientArea()!=null){
setClientArea(getClientArea()+"\n"+write);
setClientField("");
}else {
setClientArea(write);
setClientField("");
}
} catch (IOException e) {
e.printStackTrace();
}
System.out.println(write);
}

I believe I understand the problem, and how to correct it.
You are using a unique thread (chatHandler) for each new connection.
This thread writes an automatic "Hello" upon connection, but thereafter is dedicated to reading messages (in the while loop you only read din) and updating the console accordingly. Since each thread is managing a reference to din, all incoming messages are OK.
However, it seems that writing back to a client (serverSend) is not in a thread; it is triggered by a button event. At this point, dout will be a reference to the most recent connection, and not a reference to the client intended to get the message. That is why the most recent client gets all future messages.
The correction is to choose the correct 'dout' for the intended client. When the server 'operator' chooses to write a message back (clicking the send button), somehow you need to obtain the correct 'dout' for that client.
One way to do this is to establish dout prior to creating the thread (using socket), and maintain a relationship between each client, and it's corresponding dout (i.e. in a Map).
If the problem is still not clear (that each client must have a unique reference to dout), please let me know and I will try to clarify.

Multithreaded Server in Java - connection timeout exception while connecting from other computer

I have a problem with my application. If I run server and clients on the same computer it works fine. No errors. But if I run server on one PC and I try to connect form other computers I get "timeout exception" or If I manage to connect I will get errors while sending data.
Server code (not all):
// server loop - listening for connections
public void runServer()
{
try {
ServerSocket serverSocket = new ServerSocket(port, 10);
System.out.println("Server up.");
while (true)
{
System.out.println("waiting for new connection...");
Socket socket = serverSocket.accept();
System.out.println("Someone connected");
Thread t = new Thread (new ServerThread(socket));
t.start();
System.out.println("new thread");
}
} catch (IOException ex) {
Logger.getLogger(KsiegarniaServer.class.getName()).log(Level.SEVERE, null, ex);
System.out.println("Server error");
}
// this is thread that is opened when new client connects
private class ServerThread implements Runnable
{
Socket socket;
ObjectInputStream in;
ObjectOutputStream out;
String playerLogin;
int playerID;
public ServerThread(Socket s) {
this.socket = s;
}
public void run() {
try {
Msg m;
in = new ObjectInputStream(socket.getInputStream());
out = new ObjectOutputStream(socket.getOutputStream());
System.out.println("Streams are ready!");
while ( (m = (Msg) in.readObject()).getHeader() != 0 )
{
respondToClient(m); // switch with cases that are running depending on message header
}
} catch (IOException ex) {
//Logger.getLogger(SpaceBattleGameServer.class.getName()).log(Level.SEVERE, null, ex);
System.out.println("IOException - public void run()");
} catch (ClassNotFoundException e) {
System.out.println("ClassNotFoundException - public void run()");
} finally {
// other stuff
}

How to start Server Application on Windows

I created a simple Client-Server Application, which is working fine.
The server is listening to a port and then starts a thread for the job.
At the moment the only way (outside the IDE) is, to kill the java.exe to stop the server.
Both example classes are very stripped-down.
Main Class:
public static void main(String[] args) {
MultiThreadedServer server = new MultiThreadedServer(9000);
new Thread(server).start();
}
MultiThreadedServer Class:
public class MultiThreadedServer implements Runnable {
protected int serverPort = 9000;
protected ServerSocket serverSocket = null;
protected Thread runningThread = null;
protected ExecutorService threadPool = Executors.newFixedThreadPool(Options.getInstance().getThreadCount());
public MultiThreadedServer(int port) {
this.serverPort = port;
}
public void run() {
synchronized (this) {
this.runningThread = Thread.currentThread();
}
openServerSocket();
while (true) {
Socket clientSocket;
try {
clientSocket = this.serverSocket.accept();
} catch (IOException e) {
throw new RuntimeException("Error accepting client connection", e);
}
try {
this.threadPool.execute(new WorkerRunnable(clientSocket, Constants.appName + " Thread"));
} catch (Exception e) {
e.printStackTrace();
}
}
}
private void openServerSocket() {
try {
this.serverSocket = new ServerSocket(this.serverPort);
} catch (IOException e) {
throw new RuntimeException("Cannot open port " + serverPort, e);
}
}
}
I am wondering, what is the best practice to start the server application?

I have solved it on my own.
I´ve created a windows batch script, which processes some pre-requirements and starts the server application.
And with nssm nssm I have installed this batch file as windows service. Not the server application is controllable by windows services.