Currently I have the following code, working with Node.js, socket.io and Redis:
var io = require('socket.io'), redis = require("redis"), client = redis.createClient();
io.sockets.on('connection', function (socket) {
var socket_id = socket.id;
socket.on('chat', function(data) {
client.set('user:' + socket_id, data['colour']);
// The user left the page. Remove them from Redis.
socket.on('disconnect', function () {
client.del('user:' + socket_id);
client.quit();
});
});
});
This works fine for normal socket connections and disconnections, but there seems to be a problem if Node goes down, or if I just restart Node as part of normal development.
The key is never deleted from Redis. So the number of entries stored in the Redis database gradually grows and grows. I'm also not sure whether the Redis client exists cleanly.
How can I clean up Redis entries and quit the Redis client when Node exits, as well as when the socket disconnects?
You could handle this when node exits, but e.g. in case the power goes down, there's no way you can clean it up at shutdown time. I'd wipe old stuff from the DB at startup time instead.
I've run in to this problem too. My solution was to just use a specific Redis database on the server for Socket.io data. A simple FLUSHDB to that database on start up will clean out stuck keys.
var socketIoDatabase = 4;
var client = redis.createClient();
client.select(socketIoDatabase);
client.flushdb();
Of course if you have multiple node processes using this same database clearing it will cause problems. In this case you can do it during a maintenance window or something while all node processes are terminated.
check this out:
http://nodejs.org/docs/v0.4.12/api/process.html#event_uncaughtException_
var io = require('socket.io'), redis = require("redis"), client = redis.createClient();
io.sockets.on('connection', function (socket) {
var socket_id = socket.id;
socket.on('chat', function(data) {
client.set('user:' + socket_id, data['colour']);
// The user left the page. Remove them from Redis.
socket.on('disconnect', function () {
client.del('user:' + socket_id);
client.quit();
});
});
});
// this will be activated on any error without try catch :)
process.on('uncaughtException', function (err) {
console.log('Caught exception: ' + err);
});
Related
Good day, everyone.
I wanted to know if this was possible in Node.js. Suppose I have two different node applications, and they are both going to compete to be a server on a certain port. Whichever reaches the port first becomes the server, and the other one automatically becomes a client of that server.
Here is a simple diagram of what I am trying to explain:
So in this example, process 1 becomes the server because it reached the port first. Process 2 automatically becomes Process 1's client. However, I also want the functionality that if anything happens to Process 1 and the connection fails, then Process 2 becomes the new server on that same port.
Here is a diagram on what I mean:
Here is the code I have so far:
var net = require('net');
var TIMEOUT_TIME = 3000; // in milliseconds
var PORT_NUMBER = 1337;
// Attempt to create server.
var application1 = net.createServer(function (socket) {
socket.write('Hello Server 1\r\n');
socket.end("hello");
console.log("Someone connected to Server 1. \n");
socket.pipe(socket);
});
application1.listen(PORT_NUMBER, function(){
console.log("\nServer 1 is now the official server. \n");
setTimeout(function() {
application1.close();
console.log("Server 1 has been closed.");
}, TIMEOUT_TIME);
})
.on('error', function(err) {
console.log('there was an error.');
if(portIsUsed(err)) {
console.log("Port Was In Use! (This is Server 1 trying to connect.)");
net.connect(PORT_NUMBER, function() {
console.log("Server 1 connected to port.\n");
});
}
})
.on('end', function() {
console.log("server 1 disconnected from port");
});
// Attempt to create server.
var application2 = net.createServer(function (socket) {
socket.write('Hello Server 2\r\n');
socket.end("hello");
console.log("someone went into application2.");
socket.pipe(socket);
});
application2.listen(PORT_NUMBER, function() {
console.log("\nServer 2 is now the official server. \n");
})
.on('error', function(err) {
if(portIsUsed(err)) {
console.log("Port Was In Use! (This is Server 2 trying to connect.)\n");
net.connect(PORT_NUMBER, function() {
console.log("Server 2 connected to port.\n");
})
.on("end", function() {
// code here for when the connection ends?
});
}
})
.on('end', function() {
console.log("server 2 disconnected from port");
});
function portIsUsed(err) {
return err.code === "EADDRINUSE";
}
Application2 successfully detects the EADDRINUSE error (because Application1 connects first, so the port is used), but how do I make become the new server in the case that Application1 drops? I tried using .on("end", ...) inside the .on("error",...) in application2, but its not working.
Is this even possible in Node.js, due to its single-threaded nature? In the Node API I saw that cluster was used to work on more than 1 thread if I had a multicore machine. Should I use that instead?
I'm new to Node.js, so any help pointing me the right way would be appreciated.
Thank you,
I saw You're trying to write same app twice to be able handle request and balance between them.
So thats solution:
write normal single-threaded app and then run it using pm2 (https://github.com/Unitech/pm2):
install
npm install pm2 -g
run
pm2 start app.js -i max
use keymetrics (https://keymetrics.io/):
pm2 interact public_key secret_key
doing app that trying to dominate on port is not good approach, even when You're switching roles from server to client.
it's better to know that one app runs on one port and another on second port and it's normal.
i am trying to get a chat program to work using socket.io but it doesnt seem to work properly.
i am using a Node.js server and it seems to be running properly. i think this may have something to do with emitting to rooms.
the code i have on the client browser is:
<script>
var socket = io("https://localhost:3000/userChat");
socket.on('connect', function(){
socket.emit('initialiseConnection', "user1");
});
socket.on('messageIn', function(msg){
console.log(msg);
$('#messages').append($('<li>').text(msg.message));
});
</script>
so when the page loads, socket.io it connects to the server and emits the "initialiseConnection" event on the server with "user1". which is a new room specifically for that user.
on the server, the code i have handling "initialiseConnection" is:
socket.on("initialiseConnection", function(username){
socket.join(username);
console.log(username + " has joined.");
Message.find({recipient:username}, function (err, message){
console.log("messages for "+username+": "+message.length);
for (var x = 0; x < message.length; x++){
console.log(username+"'s message "+x);
console.log(message[x]);
socket.to(username).emit("messageIn", {"message":message[x]});
}
});
});
this code as you can see, creates and joins a room with the same name as the username. the looks in the database for any messages, and tries to emit those messages to the user. i log the message. there is definately a message and the username in the "socket.to()" method is also correctly shown in the logs. but the "socket.on('messageIn')" on the client browser doesnt seem to be picking up the event.
i have also tried putting:
setTimeout(function() {
socket.to(username).emit("messageIn", {"message":"test message"});
}, 5000);
immediately after the socket.join(), in case this was related to some backbround processing that needed to complete
can anyone see where i may have gone wrong on this?
Thanks.
--EDIT 1--------------------------------------
var https = require('https');
var express = require('express');
var app = express();
var server = https.createServer(https_options, app).listen(3000);
var io = require('socket.io')(server);
var userChat = io.of("/userChat");
userChat.on('connection', function(socket){
console.log('a user connected');
socket.on("initialiseConnection", function(username){
...
});
socket.on('disconnect', function(){
socket.leave(socket.room);
});
});
You need to change this:
socket.to(username).emit("messageIn", {"message":message[x]});
to this:
socket.emit("messageIn", {"message":message[x]});
A socket is the endpoint. When sending, you just send directly to the socket. You don't send to a user in a room? You just send to a socket. Since you already have the socket in your socket variable, that's what you send to.
I couldn't find a clear answer on Google or SO.
I know a net.Server instance has a close method that doesn't allow any more clients in. But it doesn't disconnect clients already connected. How can I achieve that?
I know how this can be done with Http, I guess I'm asking if it's the same with Tcp or if it's different.
With Http, I'd do something like this:
var http = require("http");
var clients = [];
var server = http.createServer(function(request, response) {
response.writeHead(200, {"Content-Type": "text/plain"});
response.end("You sent a request.");
});
server.on("connection", function(socket) {
socket.write("You connected.");
clients.push(socket);
});
// .. later when I want to close
server.close();
clients.forEach(function(client) {
client.destroy();
});
Is it the same for Tcp? Or should I do anything differently?
Since no answer was provided, here is an example of how to open and (hard) close a server in node.js:
Create the server:
var net = require('net');
var clients = [];
var server = net.createServer();
server.on('connection', function (socket) {
clients.push(socket);
console.log('client connect, count: ', clients.length);
socket.on('close', function () {
clients.splice(clients.indexOf(socket), 1);
});
});
server.listen(8194);
Close the server:
// destroy all clients (this will emit the 'close' event above)
for (var i in clients) {
clients[i].destroy();
}
server.close(function () {
console.log('server closed.');
server.unref();
});
Update: Since using the above code, I've ran into an issue that close will leave the port open (TIME_WAIT in Windows). Since I'm intentionally closing the connection, I'm using unref as it appears to fully close the tcp server, though I'm not 100% if this is the correct way of closing the connection.
I am using NodeJS v16.13.2 ... When the process containing the server code exits, all clients connection are closed/destroyed by default.
I came here to find out how I could listen for a server.("exit", myTaskCallback), since I wanted to delete some files while exiting the server. But the answer I have found is that such event does not exists. I had to listen to process.on('exit', myTaskCallback) to do the job.
sock.end(); //to correctly send the end of the connection in both sides
sock.on("close", fn) //add event listeners to destory all related sockets and clients
sock.on("close", () => { sock.destroy() }) //to destroy your side socket wrapper
Example:
const closeConn = async (sock, cb) => {
sock.ev.on("close", async ()=>{
await sock?.destroy();
if (typeof cb === "function") cb();
});
await sock?.end();
}
closeConn(sock, openSock);
You can check more here
I have a problem that i don't seems to be able to solve it. I'm doing some kind of integration with remote system and my code is in iframe but that can't be important for this one i hope :).
I'm trying to send a message from server to specific room/client to begin session. First thing I do is when user log in, I emit message from client side with username.
CLIENT.JS
conn.on('connect', function () {
conn.emit('session', { username: 'some_username' });
}, false);
And on server side i get message and join socket to the room.
SERVER.JS
socket.on('session', function(session) {
socket.join(session.username);
});
I have another module that communicates with this server.js script through redis. So i have two more events in server.js
SERVER.JS
var userCreate = redis.createClient();
userCreate.subscribe("userCreate", "userCreate");
var userDestroy = redis.createClient();
userDestroy.subscribe("userDestroy", "userDestroy");
userCreate.on("message", function(channel, data) {
socket.to(JSON.parse(data).username).emit('beginSession', data);
});
userDestroy.on("message", function(channel, data) {
socket.to(JSON.parse(data).username).emit('endSession', data);
socket.leave(JSON.parse(data).username);
});
But when ever i try to emit message from server to client i broadcast message to everyone. What am I doing wrong?
Well, from the syntax point of view you are doing everything correct.
Didn't you forget to specify the userId property in the endSession?
userDestroy.on("message", function(channel, data) {
socket.to(JSON.parse(data).userId).emit('endSession', data);
socket.leave(JSON.parse(data).userId);
});
If that doesn't work - you should provide the contents of a data object
Is it possible for a server to connect to another using Socket.IO and be treated like a client?
And have it join rooms, recieve io.sockets.in('lobby').emit(). And more?
The first server is also listening for connections/messages as well.
Hey Brad, here's my full .js app below for reference:
var io = require("socket.io").listen(8099);
io.set('log level', 1);
io.sockets.on("connection", function (socket) {
console.log('A Client has Connected to this Server');
//Let Everyone Know I just Joined
socket.broadcast.to('lobby').emit("message",'UC,' + socket.id); // Send to everyone in Room but NOT me
socket.on("message", function (data) {
//Missing code
socket2.send('message,' + data); //Forward Message to Second Server
});
socket.on("disconnect", function (data) {
//Send Notification to Second Server
//Need to figure out later
//Send Notification to Everyone
socket.broadcast.emit("message",'UD,' + socket.id ); //Send to Everyone but NOT me
//Remove user from Session ID
arSessionIDs.removeByValue(socket.id);
//Send Notification to Console
console.log("disconnecting " + arRoster[socket.id][1]);
});
});
var io_client = require( 'socket.io-client' );
var socket2 = io_client.connect('http://192.168.0.104:8090');
socket2.on('connect', function () {
socket2.emit('C3434M,Test');
});
Yes, absolutely. Just use the Socket.IO client in your server application directly.
https://github.com/LearnBoost/socket.io-client
You can install it with npm install socket.io-client. Then to use:
var socket = io.connect('http://example.com');
socket.on('connect', function () {
// socket connected
socket.emit('server custom event', { my: 'data' });
});
I realize this is an old post, but I was working on something similar and decided to come back and contribute something as it got me thinking.
Here's a basic Client -> Server 1 -> Server 2 setup
Server #1
// Server 1
var io = require("socket.io").listen(8099); // This is the Server for SERVER 1
var other_server = require("socket.io-client")('http://example.com:8100'); // This is a client connecting to the SERVER 2
other_server.on("connect",function(){
other_server.on('message',function(data){
// We received a message from Server 2
// We are going to forward/broadcast that message to the "Lobby" room
io.to('lobby').emit('message',data);
});
});
io.sockets.on("connection",function(socket){
// Display a connected message
console.log("User-Client Connected!");
// Lets force this connection into the lobby room.
socket.join('lobby');
// Some roster/user management logic to track them
// This would be upto you to add :)
// When we receive a message...
socket.on("message",function(data){
// We need to just forward this message to our other guy
// We are literally just forwarding the whole data packet
other_server.emit("message",data);
});
socket.on("disconnect",function(data){
// We need to notify Server 2 that the client has disconnected
other_server.emit("message","UD,"+socket.id);
// Other logic you may or may not want
// Your other disconnect code here
});
});
And here's Server #2
// Server 2
var io = require("socket.io").listen(8100);
io.sockets.on("connection",function(socket){
// Display a connected message
console.log("Server-Client Connected!");
// When we receive a message...
socket.on("message",function(data){
// We got a message. I don't know, what we should do with this
});
});
This is our Client, who sends the original message.
// Client
var socket = io('http://localhost');
socket.on('connect', function(){
socket.emit("message","This is my message");
socket.on('message',function(data){
console.log("We got a message: ",data);
});
});
I am making this post a Community Wiki so that someone can improve this if they feel like it.
The code has not been tested, use at your own risk.
I had the same problem, but instead to use socket.io-client I decided to use a more simple approach (at least for me) using redis pub/sub, the result is pretty simple.
You can take a look at my solution here: https://github.com/alissonperez/scalable-socket-io-server
With this solution you can have how much process/servers you want (using auto-scaling solution), you just use redis as a way to forward your messages between your servers.