Develop Reference

client.on not getting data on single connect

I am using net module to connect client with my server. And here is my code.
const Net = require('net');
client = Net.connect(parseInt(port), host, function() {
console.log('server connected')
})
console.log("ooooooooooooooooooooooooooooo")
client.on('data', function(chunk) {
let data = chunk.toString()
console.log(data)
});
client.on('error', function(error) {
console.error('error', error);
});
The issue is when I connect it with single client it doesn't give me data inside client.on('data' but when I connect it will two or more clients it gets connected and I am getting my data. Someone pls help.
If there any other module I can use ?

I have three Java TCP servers each running on their own thread, this particular one handles localhost connections from the NodeJS server which is mainly TEXT or JSON objects. It will read a command and respond.
The NodeJS server then sends that data back to the client browser using socket.io.
/*
* Handle the nodejs interaction on localhost port 2000
*/
public class DeviceServer3 extends Thread {
private static DeviceServer dev_server = null;
private boolean quit = false;
private final int port = 2000;
public DeviceServer3(DeviceServer server) {
dev_server = server; // store original server
}
public void quitSignal() { // safely shutdown thread
System.out.println("WLMedia Node Java Server exiting...");
quit = true;
while (dev_server.thread_count.get() != 0) {
try { Thread.sleep(5);
} catch (InterruptedException ex) {}
}
}
#Override
public void run() { // main thread
ServerSocket listen_socket = null;
while (!quit) {
try {
listen_socket = new ServerSocket(port);
//listen_socket.setSoTimeout(5000);
listen_socket.setReuseAddress(true);
while (!quit) {
Socket connection = listen_socket.accept();
checkSocket(connection);
}
} catch (IOException e) {
System.out.println("Node Server catch: " + e.getLocalizedMessage());
try {
Thread.sleep(5000);
} catch (InterruptedException ex) {
}
} finally {
try {
if (listen_socket != null) {
listen_socket.close();
}
} catch (IOException e) {
System.out.println("server finally: " + e.getMessage());
}
}
}
}
private void checkSocket(Socket socket) {
// Only allow 'localhost' connections
if (socket.getInetAddress().isLoopbackAddress()) {
handleSocket(socket); // TODO change to a thread
} else {
System.out.println("WARNING: Outside connection attempt from: "
+ socket.getInetAddress().toString());
}
try {
socket.close();
System.out.println("Port 2000 socket disconnected");
} catch (IOException e) {
e.printStackTrace();
}
}
private BufferedReader getBufferedReader(Socket socket)
throws IOException {
InputStreamReader is = new InputStreamReader(socket.getInputStream());
return new BufferedReader(is);
}
private BufferedWriter getBufferedWriter(Socket socket)
throws IOException {
OutputStreamWriter os = new OutputStreamWriter(socket.getOutputStream());
return new BufferedWriter(os);
}
// Safely here to handle the socket connection
private void handleSocket(Socket socket) {
System.out.println("Port 2000 socket connected");
try {
BufferedReader br = getBufferedReader(socket);
BufferedWriter bw = getBufferedWriter(socket);
String command = br.readLine();
switch (command) {
/* Media Manager */
case "media_areas":
System.out.println("NodeJS media_areas");
get_media_areas(br, bw);
break;
case "media_categories":
System.out.println("NodeJS media_categories");
get_media_categories(br, bw);
break;
/* Device manager */
case "devices_get":
System.out.println("NodeJS get_devices");
get_devices(br, bw);
break;
default:
System.out.println("NodeJS command not recognised: " + command);
}
} catch (IOException e) {
e.printStackTrace();
}
}
/*
* Handle commands
*/
// Command: media_areas
private void get_media_areas(BufferedReader br, BufferedWriter bw)
throws IOException {
JSONArray area_list = new JSONArray(); // create JSON array
System.out.println("Getting Area list");
synchronized (dev_server.library.media_lock) {
for (Area area : dev_server.library.media) {
area_list.put(area.name);
System.out.println("Area: " + area.name);
}
}
bw.write(area_list.toString()); // send JSON array back to NodeJS server
bw.flush(); // ensure a flush before the socket is closed
}
// ...
The issue I had was the data not being sent to the Node server, which using the flush() fixed that issue before the socket was closed.
This is a snipped from the Node server which connects to the Java TCP server and then sends the JSON data back to the clients browser.
const global = require("../global/global.js");
const login = require("../login/login");
const node_port = 2000;
const host = "localhost";
function m_get_media_areas(socket) {
// check user logged in (return to login page)
if (!login.check_logged_in(socket)) { return; }
client = new global.net.Socket(); // connect to Java TCP server
client.connect({port: node_port, host: host}, () =>
{ client.write("media_areas\n"); });
// send the JSON string to clients browser over socket.io
client.on("data", (data) => { socket.emit("media_areas", data); });
client.on("end", () => {});
client.on("error", () => { console.log("ERROR: getting areas"); });
}
module.exports = {
get_media_areas : m_get_media_areas,
// ...
}
On the clients browser side I just use socket.io to emit the command and then just listent for the event so that I can use the data.
// get area list
socket.emit("media_areas");
// media variables
media_area = "";
media_category = "";
media_videos = {}; // a JSON array of JSON objects
socket.on("media_areas", (res) => {
json = JSON.parse(new TextDecoder().decode(res));
$("#list_media_area").empty();
$("#list_media_category").empty();
$("#list_media_videos").empty();
json.forEach(area => {
if (area !== null && area !== "")
$("#list_media_area").append("<li>" + area);
});
media_area = "";
$("#list_media_area li").click(function() {
$(this).addClass("li_selected").siblings().removeClass("li_selected");
media_area = $(this).text();
console.log("Media Area Selected: " + media_area);
$("#accordion_video_category").click();
socket.emit("media_categories", {"area": media_area});
});
});
That's how I've managed to get around it and it works for me great.
The Java JSON library I used is:
https://search.maven.org/classic/#search%7Cgav%7C1%7Cg%3A%22org.json%22%20AND%20a%3A%22json%22

Without more information on your server implementation it is difficult to answer this question directly. Here is a general example that should be helpful for you.
server.js
const net = require('net');
net.createServer(function(socket) {
// listen for data from the client
socket.on('data', function(data) {
console.log('data from client: ', String(data));
});
// write data to the client
socket.write('hello from the server\n');
}).listen('3000', function() {
console.log('server listening on 3000');
});
client.js
const net = require('net');
const socket = net.connect(3000, 'localhost')
// listen for data from the server
socket.on('data', function(data) {
console.log('data from server: ', String(data));
});
// write data to the server
socket.write('hello from the client\n');
First run node server.js then from a separate tab run node client.js. You should see the communication between the server and client. Another tool that may be helpful for you is telnet, which provides a simple tcp interface. You can test your server by using telnet localhost 3000

Spring WebSockets Stomp.subscribe not working

I've been trying to implement a basic Spring WebSockets application following the official Spring guide. The files I have are the following:
WebSocketConfig.java
#Configuration
#EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {
#Override
public void configureMessageBroker(MessageBrokerRegistry registry) {
registry.enableSimpleBroker("/chat");
registry.setApplicationDestinationPrefixes("/message");
}
#Override
public void registerStompEndpoints(StompEndpointRegistry stompEndpointRegistry) {
stompEndpointRegistry.addEndpoint("/ws-connect").setAllowedOrigins("*").withSockJS();
}
}
MessageController.java
#Controller
public class MessageController {
#MessageMapping(value = "/test")
#SendTo("/private")
public Message message(String messageText) {
Message message = new Message();
message.setMessage(messageText);r);
message.setTimestamp(new Date());
return message;
}
}
sockets.js
var stompClient = null;
function connect() {
var socket = new SockJS('http://localhost:8080/ws-connect');
stompClient = Stomp.over(socket);
stompClient.connect({}, function(frame) {
console.log('Connected: ' + frame);
stompClient.subscribe('/chat/private', function(message) {
console.log('Here');
console.log('Message is: ' + message);
});
console.log('Here2');
})
}
connect();
function sendMessage() {
stompClient.send('/message/test', {}, "Hello self!");;
}
I have a button in my index.html that when clicked calls the sendMessage function and I get a console log that the message has been sent, however I never get the reply in the subscribe function. The client successfully connects to the WebSocket server and I get this outputted in the console. What am I doing wrong?

Change /private to /chat/private
Change it like below :
#Controller
public class MessageController {
#MessageMapping(value = "/test")
#SendTo("/chat/private")
public Message message(String messageText) {
Message message = new Message();
message.setMessage(messageText);
message.setTimestamp(new Date());
return message;
}
}

SignalR js client wrong Server port

I'm starting with signalr but got some trouble, my test server run at http://localhost:22660/ and my web run at
http://localhost:61963/.I got this error when connect from client to server:
GET http://localhost:61963/signalr/negotiate?clientProtocol=1.4&connectionData=%5B%7B%22name%22%3A%22chathub%22%7D%5D&_=1496809403215 404 (Not Found)
I already config: $.connection.hub.url = 'http://localhost:22660/signalr'; but not work, this my js code:
var connection = $.hubConnection();
$.connection.hub.url = 'http://localhost:22660/signalr';
var chatHub = connection.createHubProxy('ChatHub');
connection.start()
.done(function () { console.log('Now connected, connection ID=' + connection.id); })
.fail(function () { console.log('Could not connect'); });
Server:
namespace test
{
public class Startup
{
public void Configuration(IAppBuilder app)
{
app.Map("/signalr", map =>
{
map.UseCors(CorsOptions.AllowAll);
var hubConfiguration = new HubConfiguration
{
EnableJSONP = true
};
map.RunSignalR(hubConfiguration);
});
}
}
}
namespace SignalRChat
{
public class ChatHub : Hub
{
public void Send(string name, string message)
{
// Call the addNewMessageToPage method to update clients.
Clients.All.addNewMessageToPage(name, message);
}
}
}

I dont sure, but i think because i using different version of signalr (2.1.2 and 2.2.0). Using same version solved my problem.

Accessing hubs - Angularjs, asp.net mvc and SignalR

I am new in using SignalR and I find it hard to setup in my application.
App.js
I got code here in my app.run(); that checks whether a user was already logged in.
LoginUserService.isLogged().then(function(msg){
if (msg.data["authenticated"]) {
var id = $cookies.get('UserId');
var TestHub= $.connection.testHub;
$.connection.hub.start()
.done(function () {
//I get the id of online user and pass it on makeOnline method in my testHub
TestHub.server.makeOnline(id);
});
}
});
controller.js
Here in my controller I made connection to the same hub in my app.js in order for me to get the online clients. This controller can be accessed by admin only
app.controller('Users',function($scope){
var hub = $.connection.testHub;
hub.client.allOnline = function (users) {
console.log("client.allonline(" + JSON.stringify(users) + ")");
}
$.connection.hub.start()
.done(function () {
})
.fail(function (error) {
console.log(error);
});
});
TestHub.cs
private static ConcurrentDictionary<string, int> _locks = new ConcurrentDictionary<string, int>();
private static object _lock = new object();
public void MakeOnline(int userid)
{
lock (_lock)
{
foreach (int id in _locks.Values)
{
if (userid == id)
{
return;
}
}
_locks.AddOrUpdate(Context.ConnectionId, userid, (key, oldValue) => userid);
Clients.All.allOnline(_locks.Values);
}
}
My codes in app.js works but whenever I go to Users controller I can't get any result in hub.client.allOnline. I tried refreshing the browser and that's the only time I got result. Any ideas what should I do?

SignalR must call .done or .fail before logic

I'm trying to create a simple hello world with SignalR. I have a hub,
public class MyHub : Hub
{
public void TestConnection(string message)
{
Clients.Caller.testConnection(message);
}
}
and a JS file (using Angular),
var hub = $.connection.myHub;
hub.client.testMessage = function (message) {
console.log("Test: " + message);
};
$.connection.hub.start().done(function () {
alert('signalR started');
}).fail(function (reason) {
console.log("SignalR connection failed: " + reason);
});
hub.server.testConnection("hello signalR").done(function () { });
When I load the page, I just want the console to say "hello signalR". I get a the error message: SignalR: Connection has not been fully initialized. Use .start().done() or .start().fail() to run logic after the connection has started.
What am I doing wrong?

Try this:
$.connection.hub.start().done(function () {
alert('signalR started');
hub.server.testConnection("hello signalR").done(function () { });
});
And on the server :
Clients.All.testConnection(message);
Functions from hub.server must be called after the connection has been started. In your example the javascript was being run but the hub connection hasn't finished starting so you put it in the callback to the .done()

This may not solve the issue but you should be calling testMessage from the C# method, not testConnection.