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After successfully establishing a socket connection, how does the server actively send string messages to the client?

I am building a server. I hope that after the Java server and the C# client are connected, I can send information from the HTML to the Java server, and then the Java server sends this information to the client.But I can't get the socket after the successful establishment in the service layer, so my Java server can only send fixed information to the client.
I tried using Class object = new Class(); object.setObject(socket); to save the socket, but when I call this object in the service layer, I get null;
I tried to save the socket using (Map) socket.put("socket", socket), but when I call this method in the service layer, I get null.
This is the code to make the socket. from SocketThread.java
public void run() {
ServerSocket serverSocket = null;
try{
serverSocket = new ServerSocket(5656);
LOGGER.info("socket server start, monitor 5656 port ! ");
Socket socket = serverSocket.accept();
new SocketClientRequest(socket).start();
LOGGER.info("send success ! ");
}catch (Exception ex){
LOGGER.error("send fail ! ");
}
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
LOGGER.error("服务器延时重启失败 ! ");
}
}
This is a method of reading the information sent by the client using the socket and sending the information to the client. from SocketClientRequest.java
public void run() {
try {
//获取socket中的数据
bufferedInputStream = new
BufferedInputStream(socket.getInputStream());
byte[] clientCharStream = new byte[messageLengthBytes];
bufferedInputStream.read(clientCharStream);
System.out.println(new String(clientCharStream, "utf-8"));
OutputStream out = socket.getOutputStream();
out.write(new String("welcome_send_server!").getBytes());
} catch (IOException e) {
LOGGER.error("read massage error [{}]", e);
}
}
Create a connection when the project starts
#EnableScheduling
#SpringBootApplication
public class GzserverApplication {
public static void main(String[] args) {
SpringApplication.run(GzserverApplication.class, args);
SocketServer socketServer = new SocketServer();
socketServer.start();
}
}
Until this step, everything is fine, but the key problem is coming.
I need to send information to the client through my controller.
this is controller
#ResponseBody
#RequestMapping(value = "firstSend)
public SResult<String> firstSend(String uName, String pNum, String time){
try{
return httpService.firstSend(uName, pNum, time);
}catch (Exception ex){
LOGGER.error(ex.getMessage(), ex);
}
return SResult.failure("fail of connect");
}
this is service
public SResult<String> firstSend(String uName, String pNum, String time) throws Exception {
String token = TokenUtil.sign(uName);
System.out.println("token code : "+token);
SocketObject socketObject = new SocketObject();
Map<String, Socket> socketMap = socketObject.socket();
Socket socket1 = socketMap.get("Socket"); // is null
Socket socket2 = socketObject.getSocket(); // is null
return SResult.success(token);
}
I hope that after the connection is successfully created, the socket can be used in the service layer, and the information is sent to the client through the socket, but no matter what I do, the socket is null in the service layer.please give me a help, thank you very much

You should not be dealing with Sockets if using Spring. Spring is a very extensive abstraction layer, that lets you avoid having to deal with the nasty details that Sockets introduce.
In your controller, you call: SocketObject socketObject = new SocketObject(); This creates a new object, presumably with a null-initialized Socket object. Nowhere in this code do you pass a socket object from the main() scope to any other scope (for example using a method named setSocket(Socket socket).
However, and I cannot stress this enough, you should not use Sockets in Spring. Think about what problem you are trying to solve, and ask yourself (why do I need to send information to the client). It is likely that Spring has a module that will do this for you in a much more scalable and manageable way.
For example, perhaps you need to establish 2-way communication between the server and the client, and need to post information to the client periodically. In this case, the WebSocket protocol (and associated Spring Websocket library) might be for you.
This is likely an XY problem. If you edit your question to illustrate the functionality you are trying to implement, it may be easier to help

Sending a string through a socket using TCP

I am trying to send a string (and later also an image) from one Android app, to another Android app. I know that I am very close.
The code "SendString" is one Android app on one phone. And the code "AppListener" is on the other phone. "SendString" seems to be working correctly and sending the string because all of my print statements are printing.
"SendString", which is sending a string to "AppListener":
(the string that I am sending "applicationName" is getting passed to "SendString" from a different activity in the project)
I know this code is working because I get all the print statements in "try" and it never gets passed to the catch Exception.
public class SendString extends AsyncTask<String, String, String> {
#Override
protected String doInBackground(String... params) {
Log.d("tag_name", "Entered AsyncTask");
String applicationName = params[0];
// SEND APPLICATION NAME AND ICON TO OTHER APP
try {
Log.d("tag_name", "TRY TO SEND STRING");
Socket socket = new Socket("192.168.0.26", 1755);
DataOutputStream DOS = new DataOutputStream(socket.getOutputStream());
DOS.writeUTF(applicationName);
Log.d("tag_name", "Application Name Sent!");
socket.close();
}
catch (Exception e){
Log.d("tag_name", "Did not send string");
}
return null;
}
}
Here is the other Android app code that is listening for a port connection, and then it should be receiving the string from "SendString".
public class AppListener extends AsyncTask<String, String, String> {
#Override
protected String doInBackground(String... uri) {
String msg_received = null;
System.out.println("LISTENING FOR LAST INSTALLED APP");
try {
System.out.println("TRY");
ServerSocket socket = new ServerSocket(1755);
System.out.println("Connect to Socket and listening");
Socket clientSocket = socket.accept(); //This is blocking. It will wait.
System.out.println("This should print after connection");
DataInputStream DIS = new DataInputStream(clientSocket.getInputStream());
msg_received = DIS.readUTF();
System.out.println("Message from server" + msg_received);
clientSocket.close();
socket.close();
} catch (Exception e) {
System.out.println("Did not connect to SendString");
}
System.out.println("Return Statement is Reached");
return msg_received;
}
}
The problem is that it seems to be getting stuck at the line
Socket clientSocket = socket.accept(); //This is blocking. It will wait.
because I never get the print statement "this should print after connection", but I get all the print statements before that. Does anyone see what the problem is and why my AppListener activity seems to not connect to the port to receive the string, even though I know that the "SendString" app is connecting and sending the string as it should be (because I see all the print statements).

Does anyone see what the problem is and why my Client seems to not connect to the port to receive the string, even though I know that the server side is connecting and sending the string as it should be.
You have 'server' and 'client' mixed up. Clients connect: servers accept.
Your real server, which you described as your client, isn't accepting a connection.
This can only mean that your real client, which you described as your server, isn't creating one.
You must have either not executed your real client at all, or else got a ConnectException you haven't told us about.

AngularJS ngWebscoket not send message to all user

I am using ngWebsocket for listening user actions and update all users page according to current action not just page that who send action.
And I make a end point in java who catch all actions and send message all open sessions. but when i testing, end point find sessions and send message to all of them but message just come to person who send action.
my java code like
#OnMessage
public String onMessage(Session session, String message) { Gson gson = new Gson();
SocketMessage sm = gson.fromJson(message, new SocketMessage().getClass());
if (sm.getEvent().equals("teklif")) {
Set<Session> openSessions = session.getOpenSessions();
for (Session openSession : openSessions) {
try {
openSession.getBasicRemote().sendText("{\"event\":\"teklif\",\"data\":" + sm.getData() + "}");
} catch (Exception ioe) {
System.out.println(ioe.getMessage());
}
}
}
return message;
}`
when i debug Set<Session> openSessions = session.getOpenSessions(); it show me two session and send message to all remote. And I listen in my controller
$rootScope.ws.$on('teklif', function (data) { console.log(data);
});
it is shown only person who emit the message
note : I send message like this -->$rootScope.ws.$emit('teklif', data.content);
How can I make this socket that all user listen all actions ?
Thanks in advance.

Your are using Session.getOpenSessions(). The Javadoc states:
Return a copy of the Set of all the open web socket sessions that
represent connections to the same endpoint to which this session
represents a connection. The Set includes the session this method is
called on. These sessions may not still be open at any point after the
return of this method. For example, iterating over the set at a later
time may yield one or more closed sessions. Developers should use
session.isOpen() to check.
So it does not give you the set of all client sessions connected to your endpoint.
Instead you need to keep track of all session connected to your endpoint for yourself and iterate over that set. Here is an example.

I found my problem what is it .
#OnMessage
public String onMessage(Session session, String message) {
Gson gson = new Gson();
SocketMessage sm = gson.fromJson(message, new SocketMessage().getClass());
if (sm.getEvent().equals("teklif")) {
//SoncketTestMessage fromJson = gson.fromJson(test.getData(), SoncketTestMessage.class);
Set<Session> openSessions = session.getOpenSessions();
for (Session openSession : openSessions) {
try {
SocketResponse rsp = new SocketResponse();
rsp.setEvent("teklif");
rsp.setData(gson.toJson(sm.getData()));
//openSession.getBasicRemote().sendText("{\"event\":\"teklif\",\"data\":" + sm.getData() + "}");
openSession.getBasicRemote().sendText(gson.toJson(rsp, SocketResponse.class));
} catch (Exception ioe) {
System.out.println(ioe.getMessage());
}
}
}
return null;
}
i made a mistake at
openSession.getBasicRemote().sendText("{\"event\":\"teklif\",\"data\":" + sm.getData() + "}");
i just changed sm.getData and send right json format then it send to all user.
It send just to owner before because of that function return message and it is at right format and only owner get the return. Now all user are getting the message.

My server stops working when reading .accept(), using Sockets

please excuse my writing errors...
I'm using NetBeans to run a homemade server and a client, and it all works fine. As I said before, I'm using "Socket" on my client, and "ServerSocket" on my sv. I'm also using JDBC Mysql in the server.
The problem starts when I generate both java files in their distributable folders and use them. The client sends information to the server (it starts with .getOutputStream() and .getInputStream(), then .flush() ), but the server doesn't receive any message. I tried seeing where it stops and it's in
clients[i] = new Client (server.accept(), i);
The crazy thing happens when I try executing my server from NetBeans and the client from my desktop... It works! So the server must be the problem. I'm also using an opened UDP port, and i'm looking for the IP of the server on 192.168.0.10 (which is my computer, in LAN).
I hope someone can help me, thanks in advance!
Here I paste my code, i'm sorry some variables are in spanish:
public ServidorMultiCliente() {
super("Servidor MultiCliente");
initComponents();
try{
servidor = new ServerSocket( 500, maxNumberClients);
}catch(IOException excepcion){
excepcion.printStackTrace();
System.exit(1);
}
serverWriteBox.append("Server iniciated, waiting for connections..."); }
I run these, from the Server:
public void ejecutar(){
clientsAcceptor.start();
messagesListener.start(); }
Where clientsAcceptor is:
private class aceptadorClientes extends Thread{
public void run(){
for( int i = 1; i < maxNumberClients; i++ ){
try{
clientes[i] = new Cliente (servidor.accept(), i); // **Here it stops**
// It never reaches here... (without using NetBeans)
clientes[i].start();
clientes[i].aceptado = true;
}catch(IOException excepcion){
excepcion.printStackTrace();
}
}
That's how I accept clients in different threads. I make the same thing with messageListener, which is a new thread for every new client. It's in a loop, always listening. And here I paste my executable Client, which is different from the Cliente class I was using in ServidorMultiCliente:
public Cliente(){
}
public Cliente(String host){
this.host = host;
this.executeConnection();
}
public void executeConnection(){
int connect = 0;
try {
cliente = new Socket(InetAddress.getByName(host), 500);
conectar = 1;
} catch (IOException ex) {
conectar = 0;
this.ejecutarConexion();
}
if(conectar == 1){
obtainFlows();
}
}
private void obtainFlows(){
try{
output= new ObjectOutputStream( cliente.getOutputStream());
output.flush(); // Here I should be "connected"
input = new ObjectInputStream(cliente.getInputStream());
} catch(IOException ex){
this.initiateDisconnection();
}
sendFlows("I'm connected!");
new messageListener().start(); // This is a thread
}

ServerSocket#accept is a blocking call. It listens to a port and returns a Socket when a client connects. You don't show very much of your server logic but it seems you put clients in an array so you obviously want to support more than one client. You don't show if your Client class starts a thread and returns immediatly.
You should have a server loop that just listens to a server socket and creates clients after it retrieved a client socket. Even if you do this in your Client constructor (I can't tell without the code) it is not a very good place for this and seriously hinders debugging.
If you don't start threads for your clients this would explain a server that "stops" (if "stops" means "blocks" and not "crashes"). See "Writing the Server Side of a Socket" in the Java Tutorial for a detailed explanation.
I can't think of why it behaves different when started via Netbeans. A little bit more of code context is needed.

Receiving SMS Messages using WMA in Java ME

I am trying to develop a sms sending and receiving test application in J2ME using the WMA API. I have separate threads for sending and receiving.
The Sending thread's run method -
public void run() {
try {
MessageConnection connection = (MessageConnection) Connector.open("sms://+" + number + ":1234");
BinaryMessage messageBody = (BinaryMessage) connection.newMessage(connection.BINARY_MESSAGE);
messageBody.setPayloadData(message.getBytes());
connection.send(messageBody);
connection.close();
} catch (IOException ex) {
}
}
The receiving thread's run method
public void run() {
try {
while (true) {
MessageConnection connection = (MessageConnection) Connector.open("sms://:1234");
BinaryMessage messageBody = (BinaryMessage) connection.receive();
message = new String(messageBody.getPayloadData());
number = messageBody.getAddress();
number = number.substring(6, 15);
App.setDisplay(number, message);
connection.close();
}
} catch (IOException ex) {
ex.printStackTrace();
}
}
I am initializing the receiving thread in the startApp() and initializing the sending thread when the send command is pressed. The problem I have is that if I use two Emulators, both sides can't send messages. One emulator can continuously send messages to the other but when the other emulator tries to send a message the message isn't received.
When a message is received by the emulator console shows -
[INFO] [sms ] ## javacall: SMS
sending...
when that line appears the emulator doesn't receive any messages. Where is the problem in my code?
PS: I saw that their is a way to use a listener to work around this problem with using a separate thread for receiving but I want to know where is the problem is in the above code?
Any help is really appreciated ^^

If you are running in emulator, use wma console available to send or receive messages. You can't do it from emulator to emulator. wma console is available at
utilities -> wma console

I found the problem... It's because SMS doesn't work in Netbeans above versions. It only works in Netbeans 6.1 ... Something is wrong with the emulator