I am trying to create a websocket connection from JavaScript code to a Java server. I have managed to do this with a unsecure ws connection, but because the website that I want to use this code on is a secure https side, I have to use a secure websocket.
I have spend quite some time on research trying to get this to work, however I can't figure out how to get them connected. I have absolutely no experience with stuff like keystores or ciphers, but I don't need that security, I don't want to send any sensitive data.
Anyways, here is what I've tried:
SLLServerSocket server = (SSLServerSocket) SSLServerSocketFactory
.getDefault().createServerSocket(1234);
SSLSocket client = (SSLSocket) server.accept();
with corresponding JavaScript code:
var socket = new WebSocket("wss://localhost:1234")
socket.onopen = () => console.log("Connected");
socket.onmessage = m => console.log("Message received:", m);
Running this resulted in a Caused by: javax.net.ssl.SSLHandshakeException: No available authentication scheme which I managed to fix by adding
System.setProperty("jdk.tls.server.protocols", "TLSv1.2");
Now I am getting the exception javax.net.ssl.SSLHandshakeException: no cipher suites in common. I've done some research on that as well but whatever I find seems assume that a keystore or something is already there, which it is not for me. In fact I don't really know what encryption it should use, I did not find anything about that
To be fair, part of the problem may very well be that I don't know what to actually search for, but that is why I am asking. There are already articles about these exceptions I am showing, I know them, and they didn't help.
I have been trying to create an online game but when I try to use socket.on(...); or socket.emit(...) it comes up with an error like what is socket. I have seen some posts similar to this one and tried all the solutions but none worked. I have already got io.connect(...); working and it works (I assume this means I have properly set up socket.io-client). I just don't see what I am doing wrong. If you need the code you can simply request it though I don't think it was necessary. Thanks.
To use SocketIO on the client-side, first import it via
import * as io from 'socket.io-client';
Then, probably in a constructor, establish a connection to the server's ip and port running the SocketIO server
const socket = io(`172.16.1.3:81`);
Also in the constructor you will likely want to setup a function to be called when the server sends a certain message type:
socket.on("update-player", handlePlayerUpdateFunction);
and
function handlePlayerUpdateFunction(message) {
console.log(`Received message from server: ${message}`);
}
If this client does not receive the message sent from your server, then something is wrong with your server not being set up correctly to listen on the port.
After trying some things and doing some research I found the solution to my problem. Adding in var socket = io.connect(x.x.x.x:3000); my code started functioning and everything was perfect I had already imported socket.io-client trough CDNJS link on the installation guide. I just had to Initialise the variable.
On my client (a phone with a browser) I want to see the stats of the server CPU,RAM & HDD and gather info from various logs.
I'm using ajax polling.
On the client every 5 sec (setInterval) I call a PHP file:
scan a folder containing N logs
read the last line of each log
convert that to JSON
Problems:
Open new connection every 5 sec.
Multiple AJAX calls.
Request headers (they are also data and so consume bandwidth)
Response headers (^)
Use PHP to read files every 5 sec. even if nothing changed.
The final JSON data is less than 5 KB, but I send it every 5 sec, and there are the headers and new connection every time, so basically every 5 sec., I have to send 5-10 KB to get 5 KB which are 10-20 KB.
Those are 60 sec / 5 sec = 12 new connections per minute and about 15 MB per hour of traffic if I leave the app open.
Lets say I have 100 users that I let monitor / control my server that would be around 1.5 GB outgoing traffic in one hour.
Not to mention that the PHP server is reading multiple files 100 times every 5 sec.
I need something that on the server reads the last lines of those logs every 5 sec and maybe writes them to a file, then I want to push this data to the client only if it's changed.
SSE (server sent events) with PHP
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
while(true){
echo "id: ".time()."\ndata: ".ReadTheLogs()."\n\n";
ob_flush();
flush();
sleep(1);
}
In this case after the connection is established with the first user
the connection keeps open (PHP is not made for that) and so I save some space (request headers,response headers). This work on my server bu most server don't allow to keep the connection open for long time.
Also with multiple users I read the log multiple times.(slowing down my old server)
And I can't control the server ... I would need to use ajax to send a command...
I need WebSockets!!!
node.js and websockets
using node.js, from what i understand, i can do all this without consuming alot
of resources and bandwich. The connection keeps open so no unnecessary headers, i can recieve and send data.it handles multiple users very well.
And this is where i need your help.
the node.js server should in background update, and store the logs data every 5 sec if the files are modified.OR should that do the operating system with (iwatch,dnotify...)
the data should be pushed only if changed.
the reading of the logs should be happen only one time after 5 sec ... so not triggered by each user.
this is the first example i have found.....and modified..
var ws=require("nodejs-websocket");
var server=ws.createServer(function(conn){
var data=read(whereToStoreTheLogs);
conn.sendText(data)// send the logs data to the user
//on first connection.
setTimeout(checkLogs,5000);
/*
here i need to continuosly check if the logs are changed.
but if i use setInterval(checkLogs,5000) or setTimeout
every user invokes a new timer and so having lots of timers on the server
can i do that in background?
*/
conn.on("text",function(str){
doStuff(str); // various commands to control the server.
})
conn.on("close",function(code,reason){
console.log("Connection closed")
})
}).listen(8001);
var checkLogs=function(){
var data=read(whereToStoreTheLogs);
if(data!=oldData){
conn.sendText(data)
}
setTimeout(checkLogs,5000);
}
the above script would be the notification server, but i also need to find a solution to store somwhere the info of those multiple logs and do that everytime something is changed, in the background.
How would you do to keep the bandwich low but also the server resources.
How would you do?
EDIT
Btw. is there a way to stream this data simultaneosly to all the clinets?
EDIT
About the logs: i also want to be able to scale the time dilatation between updates... i mean if i read the logs of ffmpeg i ned the update every sec if possible... but when no conversion is active.. i need to get the basic machine info every 5min maybe ... and so on...
GOALS:
1. performant way to read & store somewhere the logs data (only if clinets connected...[mysql,file, it's possible to store this info inside the ram(with node.js??)]).
2. performant way to stream the data to the various clients (simultanously).
3. be able to send commands to the server.. (bidirectional)
4. using web languages (js,php...), lunix commands( something that is easy to implement on multiple machines).. free software if needed.
best approach would be:
read the logs, based on current activity, to the system memory and stream simultaneously and continuosly, with an already open connection, to the various clients with webSockets.
i'don't know anything that could be faster.
UPDATE
The node.js server is up and running, using the http://einaros.github.io/ws/ webSocketServer implementation, as it appears to be the fastest one.
I wrote with the help of #HeadCode the following code to handle properly the client situation & to keep the process as low as possible. checking various things inside the broadcast loop. Now the pushing & the client handling is at a good point.
var
wss=new (require('ws').Server)({port:8080}),
isBusy,
logs,
clients,
i,
checkLogs=function(){
if(wss.clients&&(clients=wss.clients.length)){
isBusy||(logs=readLogs()/*,isBusy=true*/);
if(logs){
i=0;
while(i<clients){
wss.clients[i++].send(logs)
}
}
}
};
setInterval(checkLogs,2000);
But atm i'm using a really bad way to parse the logs.. (nodejs->httpRequest->php).. lol. After some googling i found out that i totally could stream the output of linux software directly to the nodejs app ... i didn't checked... but maybe that would be the best way to do it. node.js also has a filesystem api where icould read the logs. linux has it's own filesystem api.
the readLogs()(can be async) function is still something i'm not happy with.
nodejs filesystem?
linuxSoftware->nodejs output implementation
linux filesystem api.
keep in mind that i need to scan various folders for logs and then parse somehow the outputted data, and this every 2 seconds.
ps.: i adde isBusy to the server variables in case the logReading sytem is async.
EDIT
Answer is not complete.
Missing:
A performant way to read,parse and store the logs somewhere (linux filesystem api, or nodejs api, so the i store directly into system memory)
An explaination if it's possible to stream data directly to multiple users .
apparently nodejs loops trough the clients and so (i think) sending multiple times the data.
btw is it possible/worth to close the node server if there are no clients and restart on new connections on the apache side. (ex: if i connect to the apache hosted html file a script launches the nodejs server again). doing so would further reduce the memory leaking???right?
EDIT
After some experimenting with websockets (some videos are in the comments) i learned some new stuff. Raspberry PI has the possibility to use some CPU DMA channels to to high frequency stuff like PWM... i need to somehow understand how that works.
When using sensors and stuff like that i should store everything inside the RAM, nodejs already does that?? (in a variable inside the script)
websocket remains the best choice as it's basically easely accessible from any device now, simply using a browser.
I haven't used nodejs-websocket, but it looks like it will accept an http connection and do the upgrade as well as creating the server. If all you care about receiving is text/json then I suppose that would be fine, but it seems to me you might want to serve a web page along with it.
Here is a way to use express and socket.io to achieve what you're asking about:
var express = require('express');
var app = express();
var http = require('http').Server(app);
var io = require('socket.io')(http);
app.use(express.static(__dirname + '/'));
app.get('/', function(req, res){
res.sendfile('index.html');
});
io.on('connection', function(socket){
// This is where we should emit the cached values of everything
// that has been collected so far so this user doesn't have to
// wait for a changed value on the monitored host to see
// what is going on.
// This code is based on something I wrote for myself so it's not
// going to do anything for you as is. You'll have to implement
// your own caching mechanism.
for (var stat in cache) {
if (cache.hasOwnProperty(stat)) {
socket.emit('data', JSON.stringify(cache[stat]));
}
}
});
http.listen(3000, function(){
console.log('listening on *:3000');
});
(function checkLogs(){
var data=read(whereToStoreTheLogs);
if(data!=oldData){
io.emit(data)
}
setTimeout(checkLogs,5000);
})();
Of course, the checkLogs function has to be fleshed out by you. I have only cut and pasted it in here for context. The call to the emit function of the io object will send the message out to all connected users but the checkLogs function will only fire once (and then keep calling itself), not every time someone connects.
In your index.html page you can have something like this. It should be included in the html page at the bottom, just before the closing body tag.
<script src="/path/to/socket.io.js"></script>
<script>
// Set up the websocket for receiving updates from the server
var socket = io();
socket.on('data', function(msg){
// Do something with your message here, such as using javascript
// to display it in an appropriate spot on the page.
document.getElementById("content").innerHTML = msg;
});
</script>
By the way, check out the Nodejs documentation for a variety of built-in methods for checking system resources (https://nodejs.org/api/os.html).
Here's also a solution more in keeping with what it appears you want. Use this for your html page:
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>WS example</title>
</head>
<body>
<script>
var connection;
window.addEventListener("load", function () {
connection = new WebSocket("ws://"+window.location.hostname+":8001")
connection.onopen = function () {
console.log("Connection opened")
}
connection.onclose = function () {
console.log("Connection closed")
}
connection.onerror = function () {
console.error("Connection error")
}
connection.onmessage = function (event) {
var div = document.createElement("div")
div.textContent = event.data
document.body.appendChild(div)
}
});
</script>
</body>
</html>
And use this as your web socket server code, recently tweaked to use the 'tail' module (as found in this post: How to do `tail -f logfile.txt`-like processing in node.js?), which you will have to install using npm (Note: tail makes use of fs.watch, which is not guaranteed to work the same everywhere):
var ws = require("nodejs-websocket")
var os = require('os');
Tail = require('tail').Tail;
tail = new Tail('./testlog.txt');
var server = ws.createServer(function (conn) {
conn.on("text", function (str) {
console.log("Received " + str);
});
conn.on("close", function (code, reason) {
console.log("Connection closed");
});
}).listen(8001);
setInterval(function(){ checkLoad(); }, 5000);
function broadcast(mesg) {
server.connections.forEach(function (conn) {
conn.sendText(mesg)
})
}
var load = '';
function checkLoad(){
var new_load = os.loadavg().toString();
if (new_load === 'load'){
return;
}
load = new_load;
broadcast(load);
}
tail.on("line", function(data) {
broadcast(data);
});
Obviously this is very basic and you will have to change it for your needs.
I had made a similar implementation recently using Munin . Munin is a wonderful server monitoring tool, open source too which also provides a REST API. There several plugins available for your needs monitoring CPU, HDD and RAM usage of your server.
You need to build a push notification server. All clients who are listening, will then get a push notification when new data is updated. See this answer for more information: PHP - Push Notifications
As to how you would update the data, I'd suggest using OS-based tools to trigger a PHP script (command line) that will generate an "push" the json file out to any client currently listening. Any new client logging on to "listen" will get served the current json available, until it's updated.
This way you're not subject to 100 users using 100 connections and how much ever bandwidth to poll your server every 5 seconds, and only get updated when they need to know there's an update.
How about a service that reads all the log info (via IPMI, Nagios or whatever) and creates the output files on some schedule. Then anyone that wants to connect can just read this output rather than hammering the server logs. Essentially have one hit on the server logs then everyone else just reads a web page.
This could be implemented pretty easily.
BTW: Nagios has a v nice free edition
Answering just these bits of your question:
performant way to stream the data to the various clients (simultanously).
be able to send commands to the server.. (bidirectional)
using web languages (js,php...), lunix commands( something that is easy to implement on multiple machines).. free software if needed.
I'll recommend the Bayeux protocol as made simple by the CometD project. There are implementations in a variety of languages and it's really easy to use in its simplest form.
Meteor is broadly similar. It's an application development framework rather than a family of libraries, but it solves the same problems.
Some suggestions:
Munin for charts
NetSNMP (used by Munin, but you can also use Bash and Cron to build traps that send SMS texts on alerts)
Pingdom for remote alerts about how well the server is responding to ping and HTTP checks. It can SMS text you or call a phone, as well as have call escalation rules.
I've been doing alot of testing with socketIO and have got stuck with handling situations where my node app is simply offline. The documentation provides no real insight into this issue.
So if i run my website and node app is simply not running, console.log gives:
GET http://[url]:[port]/socket.io/socket.io.js
Uncaught ReferenceError: io is not defined
This is hardly surprising, how ever what i don't understand is how to handle these errors and simply have the script try to attempt a reconnect until it finally does reconnect (if ever).
My script looks like this:
<script src="http://[url]:[port]/socket.io/socket.io.js"></script>
<script>
windows.onload = function()
{
socketio = io.connect("http://[url]:[port]");
socketio.on('connecting', function() {
console.log('trying to connect');
});
socketio.on('connect', function() {
console.log('connected');
});
}
</script>
Is there a way to handle this kind of problem ?
When the server is offline, your initial <script> tag to load the Socket.io client library fails, so you never get the io object in the first place.
To retry, you can add a new <script> tag to load the same URL again and see if it succeeds.
Better yet, copy the socket.io client library to the server hosting your HTML, so that the script will always load. You can then simply handle connection errors from io.connect().
There are a few events that you can bind to.
socket.on("connect_failed", function() {
// Do whatever you wanted to do on failure
});
For a full list of exposed events check here: exposed socket.io events
Edit
Ah, I'm sorry. I misunderstood your question. I thought you wanted to handle when the socket server was offline. If you want to handle not being able to get at the socket.io client script, maybe you could check if socket is null or undefined and handle thought that. Then also fire a setTimeout function to try and load the script asynchronously after a wait period and then check if socket is still undefined or null. Or, as the other answer suggests, pack the socket.io client library with the rest of your HTML page.
Whats the difference between socket.io and socket.io-client?
Some project I'm trying to use is using socket.io-client, but I'm used to using plain old socket.io, and it dons't really lay it out in the documentation.
The main difference I'm aware of is that with the socket.io-client library you can connect your server to another server serving socket.io events.
For example, if my server at http://localhost is emitting a data event, I can listen on another server like so:
var socket = require('socket.io')('http://localhost');
socket.on('connect', function(){
socket.on('data', function(data){
// Do something with data
});
});
and respond accordingly with the data object passed.