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SO_REUSEADDR in NodeJs using net package

I have two backends. Backend A and Backend B.
Backend B sends and receives info using a socket server running at port 4243.
Then, with Backend A, I need to catch that info and save it. But I have to also have a socket server on Backend A running at port 4243.
The problem is that, when I run Backend A after running Backend B I receive the error "EADDRINUSE", because I'm using the same host:port on both apps.
If, for Backend A I use Python, the problem dissapear because I have a configuration for sockets that's called SO_REUSEADDR.
Here we have some examples:
https://www.programcreek.com/python/example/410/socket.SO_REUSEADDR
https://subscription.packtpub.com/book/networking-and-servers/9781849513463/1/ch01lvl1sec18/reusing-socket-addresses
But, I want to use JavaScript for coding my Backend A, so I was using the net package for coding the sockets, and I can't get it to work, because of the "EADDRINUSE" error.
The NodeJS documentation says that "All sockets in Node set SO_REUSEADDR already", but it doesn't seem to work for me...
This is my code so far:
// Step 0: Create the netServer and the netClient
console.log(`[DEBUG] Server will listen to: ${HOST}:${PORT}`);
console.log(`[DEBUG] Server will register with: ${AGENT_ID}`);
const netServer = net.createServer((c) => {
console.log('[netServer] Client connected');
c.on('message', (msg) => {
console.log('[netServer] Received `message`, MSG:', msg.toString());
});
c.on('*', (event, msg) => {
console.log('[netServer] Received `*`, EVENT:', event);
console.log('[netServer] Received `*`, MSG:', msg);
});
}).listen({
host: HOST, // 'localhost',
port: PORT, // 4243,
family: 4, // ipv4, same as socket.AF_INET for python
});
// Code copied from nodejs documentation page (doesn't make any difference)
netServer.on('error', function (e) {
if (e.code == 'EADDRINUSE') {
console.log('Address in use, retrying...');
setTimeout(function () {
netServer.close();
netServer.listen(PORT, HOST);
}, 1000);
}
});
const netClient = net.createConnection(PORT, HOST, () => {
console.log('[netClient] Connected');
});
// Step 1: Register to instance B of DTN with agent ID 'bundlesink'
netClient.write(serializeMessage({
messageType: AAPMessageTypes.REGISTER,
eid: AGENT_ID,
}));
With this code, I get the following output in the terminal:
But, with the Python code, the socket connects successfully:
I don't know what to do :(
I hope I get some help here.
Edit 1
By the way, the lsof command, throws me this output for the JavaScript backend:
And this other output for the Python backend:
Edit 2
It really seems to be a problem with JavaScript. I also found this snippet:
var net = require('net');
function startServer(port, host, callback) {
var server = net.createServer();
server.listen(port, host, function() {
callback(undefined, server);
});
server.on('error', function(error) {
console.error('Ah damn!', error);
callback(error);
});
}
startServer(4000, '0.0.0.0', function(error, wildcardServer) {
if (error) return;
startServer(4000, '127.0.0.1', function(error, localhostServer) {
if (error) return;
console.log('Started both servers!');
});
});
From this post:
https://medium.com/#eplawless/node-js-is-a-liar-sometimes-8a28196d56b6
As the author says:
Well, that prints “Started both servers!” which is exactly what we don’t want.
But for me, instead of printing that, I get an error:
Ah damn! Error: listen EADDRINUSE: address already in use 127.0.0.1:4000
at Server.setupListenHandle [as _listen2] (node:net:1319:16)
at listenInCluster (node:net:1367:12)
at doListen (node:net:1505:7)
at processTicksAndRejections (node:internal/process/task_queues:84:21) {
code: 'EADDRINUSE',
errno: -98,
syscall: 'listen',
address: '127.0.0.1',
port: 4000
}
I really cannot make it to run and print "Started both servers!".
Because that's what I want my code to do.
Edit 3
This is the Python server socket: https://gitlab.com/d3tn/ud3tn/-/blob/master/tools/aap/aap_receive.py
This is the important part:
addr = (args.tcp[0], int(args.tcp[1])) # args.tcp[0] = "localhost", args.tcp[1] = "4243"
with AAPTCPClient(address=addr) as aap_client:
aap_client.register(args.agentid) # args.agentid = "bundlesink"
run_aap_recv(aap_client, args.count, args.verify_pl)
It creates an AAPTCPClient, and the only thing that AAPTCPClient does, is the following:
def __init__(self, socket, address):
self.socket = socket
self.address = address
self.node_eid = None
self.agent_id = None
def register(self, agent_id=None):
"""Attempt to register the specified agent identifier.
Args:
agent_id: The agent identifier to be registered. If None,
uuid.uuid4() is called to generate one.
"""
self.agent_id = agent_id or str(uuid.uuid4())
logger.info(f"Sending REGISTER message for '{agent_id}'...")
msg_ack = self.send(
AAPMessage(AAPMessageType.REGISTER, self.agent_id)
)
assert msg_ack.msg_type == AAPMessageType.ACK
logger.info("ACK message received!")
def send(self, aap_msg):
"""Serialize and send the provided `AAPMessage` to the AAP endpoint.
Args:
aap_msg: The `AAPMessage` to be sent.
"""
self.socket.send(aap_msg.serialize())
return self.receive()
def receive(self):
"""Receive and return the next `AAPMessage`."""
buf = bytearray()
msg = None
while msg is None:
data = self.socket.recv(1)
if not data:
logger.info("Disconnected")
return None
buf += data
try:
msg = AAPMessage.parse(buf)
except InsufficientAAPDataError:
continue
return msg
I don't see any bind, and I don't understand why the python code can call "socket.recv", but in my JavaScript code I can't do "netServer.listen". I think it should be the same.

There are things to clarify.
1.) The client uses the bind syscall where the kernel selects the source port automatically.
It does so by checking sys local_portrange sysctl settings.
1.) If you want to bind the client to a static source port, be sure to select a TCP port outside the local_portrange range !
2.) You cannot subscribe to event "*", instead you've to subscribe to the event "data" to receive messages.
For best practice you should also subscribe to the "error" event in case of errors !
These links will get you started right away:
How do SO_REUSEADDR and SO_REUSEPORT differ?
https://idea.popcount.org/2014-04-03-bind-before-connect/
So, for all beginners, who want to dig deeper into networking using node.js…
A working server example:
// Step 0: Create the netServer and the netClient
//
var HOST = 'localhost';
var PORT = 4243;
var AGENT_ID = 'SO_REUSEADDR DEMO';
var net = require('net');
console.log(`[DEBUG] Server will listen to: ${HOST}:${PORT}`);
console.log(`[DEBUG] Server will register with: ${AGENT_ID}`);
const netServer = net.createServer((c) => {
console.log('[netServer] Client connected');
c.on('data', (msg) => {
console.log('[netServer] Received `message`, MSG:', msg.toString());
});
c.on('end', () => {
console.log('client disconnected');
});
c.on('error', function (e) {
console.log('Error: ' + e.code);
});
c.write('hello\r\n');
c.pipe(c);
}).listen({
host: HOST,
port: PORT,
family: 4, // ipv4, same as socket.AF_INET for python
});
// Code copied from nodejs documentation page (doesn't make any difference)
netServer.on('error', function (e) {
console.log('Error: ' + e.code);
if (e.code == 'EADDRINUSE') {
console.log('Address in use, retrying...');
setTimeout(function () {
netServer.close();
netServer.listen(HOST, PORT);
}, 1000);
}
if ( e.code = 'ECONNRESET' ){
console.log('Connection reset by peer...');
setTimeout(function () {
netServer.close();
netServer.listen(HOST, PORT);
}, 1000);
}
});
The Client:
/* Or use this example tcp client written in node.js. (Originated with
example code from
http://www.hacksparrow.com/tcp-socket-programming-in-node-js.html.) */
var net = require('net');
var HOST = 'localhost';
var PORT = 4243;
var client = new net.Socket();
client.setTimeout(3000);
client.connect(PORT, HOST, function() {
console.log("Connected to " + client.address().address + " Source Port: " + client.address().port + " Family: " + client.address().family);
client.write('Hello, server! Love, Client.');
});
client.on('data', function(data) {
console.log('Received: ' + data);
client.end();
});
client.on('error', function(e) {
console.log('Error: ' + e.code);
});
client.on('timeout', () => {
console.log('socket timeout');
client.end();
});
client.on('close', function() {
console.log('Connection closed');
});
Best Hannes

Steffen Ullrich was completely right.
In my JavaScript code, I was trying to create a server to listen to the port 4243.
But you don't need to have a server in order to listen to some port, you can listen with a client too! (At least that's what I understood)
You can create a client connection as following:
const netClient = net.createConnection(PORT, HOST, () => {
console.log('[netClient] Connected');
});
netClient.on('data', (data) => {
console.log('[netClient] Received data:', data.toString('utf8'));
});
And with "client.on", then you can receive messages as well, as if it were a server.
I hope this is useful to someone else.

Sails js client native websocket

I'm trying to use websockets with sails-js but I can't make it work with native javascript websockets.
the tutorial example use the sails.io.js library and it goes a little bit like this:
io.socket.on('hello', function (data) {
console.log('Socket `' + data.id + '` joined the party!');
});
function sendHello () {
// And use `io.socket.get()` to send a request to the server:
io.socket.get('/websockets/hello', function gotResponse(data, jwRes) {
console.log('Server responded with status code ' + jwRes.statusCode + ' and data: ', data);
});
}
This does work, but i want to use the native javascript websockets like this:
let ws = new WebSocket("ws://localhost:1337/websockets/hello");
ws.onopen = function (e) {
console.log("[open] Connection established");
console.log("Sending to server");
ws.send("My name is John");
};
ws.onmessage = function (event) {
console.log(`[message] Data received from server: ${event.data}`);
};
ws.onclose = function (event) {
if (event.wasClean) {
console.log(`[close] Connection closed cleanly, code=${event.code} reason=${event.reason}`);
} else {
// e.g. server process killed or network down
// event.code is usually 1006 in this case
console.log('[close] Connection died');
}
};
ws.onerror = function (error) {
console.log(`[error] ${error}`);
console.log(error);
};
Clean and native javascript websockets with no library needed. Unfortunately I can't seem to make it work.
When I try to connect to sails js server using native websockets I get this message:
WebSocket connection to 'ws://localhost:1337/websockets/hello' failed: Connection closed before receiving a handshake response
Impossible to make it connect, it seems like sails js don't even get the message because i make a log when i get a new connection (using the tutorial code):
module.exports = {
hello: function (req, res) {
console.log("web socket received",req.isSocket)
// Make sure this is a socket request (not traditional HTTP)
if (!req.isSocket) {
return res.badRequest();
}
// Have the socket which made the request join the "funSockets" room.
sails.sockets.join(req, 'funSockets');
// Broadcast a notification to all the sockets who have joined
// the "funSockets" room, excluding our newly added socket:
sails.sockets.broadcast('funSockets', 'hello', { howdy: 'hi there!' }, req);
// ^^^
// At this point, we've blasted out a socket message to all sockets who have
// joined the "funSockets" room. But that doesn't necessarily mean they
// are _listening_. In other words, to actually handle the socket message,
// connected sockets need to be listening for this particular event (in this
// case, we broadcasted our message with an event name of "hello"). The
// client-side code you'd need to write looks like this:
//
// io.socket.on('hello', function (broadcastedData){
// console.log(data.howdy);
// // => 'hi there!'
// }
//
// Now that we've broadcasted our socket message, we still have to continue on
// with any other logic we need to take care of in our action, and then send a
// response. In this case, we're just about wrapped up, so we'll continue on
// Respond to the request with a 200 OK.
// The data returned here is what we received back on the client as `data` in:
// `io.socket.get('/say/hello', function gotResponse(data, jwRes) { /* ... */ });`
return res.json({
anyData: 'we want to send back'
});
}
};
How can I make sails js work with native javascript websockets?

Found a simple solution!
Used the npm package ws: npm i ws
making a new hook: sails generate hook customWebSocket
in the hook :
/**
* WS hook
*
* #description :: A hook definition. Extends Sails by adding shadow routes, implicit actions, and/or initialization logic.
* #docs :: https://sailsjs.com/docs/concepts/extending-sails/hooks
*/
const WebSocket = require('ws');
module.exports = function defineWsHook(sails) {
return {
/**
* Runs when this Sails app loads/lifts.
*/
initialize: async function () {
sails.log.info('Initializing custom hook (`WS`)');
console.log("custom hook")
const wss = new WebSocket.Server({ port: 3100 });
wss.on('connection', (socket) => {
console.log('New user connected wss');
socket.on('message', function incoming(message) {
console.log(message)
});
});
}
};
};
Done and done, now i can connect to is using native websocket!
now that i have done that i realize that the socket.io library might be better for handling errors.

How to distinguish web sockets on server

I am trying to create a server with clients. Each client has a websocket and a web worker, and each worker has an own websocket to the server.
The problem is, that i have a place on the server, where i am storing all connections
wss.on('connection', function connection(ws) {
var cid = "" + ++cid_counter;
server.users[cid] = ws;
...
}
But now they are all storing in server.users[], and i want to store clients sockets in server.users and worker sockets in server.wokers[], but i have no idea, how to distinguish there two different types of web sockets. Maybe i could send a message, when creating a new web socket or any other solutions?
Thanks in forward

You should add auth to your sockets so you can identify the client.
Refer to this: socketio-auth
You can issue unique keys to clients and workers or whoever you want and then require them to emit to "authenticate" event.
You can distinguish them by having a key "type" in the db.
From npm:
Client:
var socket = io.connect('http://localhost');
socket.on('connect', function(){
socket.emit('authentication', {username: "John", password: "secret"});
socket.on('authenticated', function() {
// use the socket as usual
});
});
Server:
var io = require('socket.io').listen(app);
require('socketio-auth')(io, {
authenticate: function (socket, data, callback) {
//get credentials sent by the client
var key = data.key;
db.findUser('Users', {secret: key}, function(err, user) {
//inform the callback of auth success/failure
if (err || !user) return callback(new Error("User not found"));
return callback(null, user);
});
}
});

Sails.js websockets work in localhost but not working after I deploy to Openshift

Summary:
I am working on an admin panel for a sails.js based website. I have configured websockets to work in my localhost. But when I deploy to openshift, only the io.socket.on('connect',...); is firing. But when I publishAdd a record, nothing is being received in the client.
Details:
Firstly some details about my configuration:
Sails.js version: 0.12.3
Node.js version: v0.10.36 (Changed it to this to match openshift's version v0.10.35)
Socket client: sails.io.js
Tried with both memory socket store and redis socket store and the behavior is the same
Current Behavior:
I am trying to enable a notification system to my application so I am using the default sails.io.js to connect a websocket (Using the default io.socket object) in my client side code I am using console.log() for now to log any events. The code looks like this in the client js file:
$(document).ready(function () {
io.sails.environment = "development";
if(window.location.hostname === "localhost") {
io.sails.url = 'http://localhost:1337';
} else {
io.sails.url = 'http://myapp-username.rhcloud.com:8000';
}
var adminSocket = io.socket;
// Access socket's connect event to initialize functions
adminSocket.on('connect', function () {
console.log("Connected to socket");
// Subscribe to admin model of current user
adminSocket.get('/admin/subscribeToModel');
});
// Access notification (adminAlerts) model's socket events
adminSocket.on('admin', function(event) {
console.log(event);
});
// Log Errors
adminSocket.on('error', function (event) {
console.log(event);
});
});
As you can see the code runs io.socket.get(...) after the socket connects. This works for both localhost and openshift and logs "Connected to socket" and also sails.io.js's default connection message. When the server turns off the client tries to reconnect as the default behavior.
io.socket.get runs a custom controller function in the admin controller:
subscribeToModel: function(req, res, next) {
if (!req.isSocket) {
console.log("Not Socket");
return res.badRequest();
}
console.log("Socket");
Admin.subscribe(req, [req.session.userid]); //Subscribes to Admin model's entry with the user's id
return res.json({message: "Subscribed"});
}
This logs "Socket" in Both openshift and localhost but the return message is not available. I don't know if subscribe works or not in openshift but it works for sure in localhost.
This is the setup. Now I built a function to test socket behavior. In admin controller I created:
createAndBroadcastNotification: function (req, res, next) {
AdminAlerts.create({
admin: req.session.admin.id,
alertHeader: 'Some Header',
alertBody: 'Some Message',
alertType: 'label-info',
url: '/somepage'
}).exec(function (err, alert) {
if (err) {
res.serverError(err);
}
Admin.findOne({ where: {id: req.session.admin.id} }).populate('alerts').exec(function (err, admin) {
if (err) {
res.serverError(err);
}
Admin.publishAdd(req.session.userid, 'alerts', alert.id);
return res.json({message: "Done"});
});
});
}
After this Both openshift and localhost are showing {message:Done} in the browser and the record is being created and associated in the mySQL database. But Only Localhost is posting this message in the console as expected:
Object {id: 1, verb: "addedTo", attribute: "alerts", addedId: 10}
Openshift is showing no such message. Neither is it showing any error messages.
I have been trying to figure out the problem for 5 days. I have not been able to find a clue as to why this is happening.
Objective:
I wish to get the console.log() message in the client to signify an alert being added.

I figured it out. For anyone facing the same or similar issue, the documentation for openshift (In the blog) is outdated. Letting sails.io.js figure out the host and port works "just fine". It returns a connection error in firefox though. Here are the changes:
// client-side-code.js
$(document).ready(function () {
// io.sails.environment = "development";
// if(window.location.hostname === "localhost") {
// io.sails.url = 'http://localhost:1337';
// } else {
// io.sails.url = 'http://myapp-username.rhcloud.com:8000';
// }
var adminSocket = io.socket;
// Access socket's connect event to initialize functions
adminSocket.on('connect', function () {
console.log("Connected to socket");
// Subscribe to admin model of current user
adminSocket.get('/admin/subscribeToModel');
});
// Access notification (adminAlerts) model's socket events
adminSocket.on('admin', function(event) {
console.log(event);
});
// Log Errors
adminSocket.on('error', function (event) {
console.log(event);
});
});

Nodejs server unable to detect connection with Pubnub+SocketIO

My nodejs server is unable to detect when a new browser connects ('connection' event) and I dont know why. I narrowed down a problem working on it for a few days and suspect that is has to due with the addition of the pubnub socket connection implemented on the browser.
The following is my server.js
var http = require('http')
, connect = require('connect')
, io = require('socket.io')
, fs = require('fs')
, uuid = require('node-uuid')
, _ = require('lodash');
// pubnub!!! (how to initialize it for use on server)
var pubnub = require('pubnub').init({
channel: "my_channel",
publish_key: "pub-key",
subscribe_key: "sub-c-key",
uuid: "Server",
origin : 'pubsub.pubnub.com'
});
pubnub.subscribe({
channel: 'my_channel',
callback: function(message) {
console.log("Message received: ", message);
},
message: 'Server ready',
presence: function(data) {
console.log("Presense: ", data);
},
connect: publish
});
// various socket.on() events omitted
var app = connect().use(connect.static(__dirname)).use(connect.directory(__dirname));
var server = http.createServer(app);
server.listen(8888);
io = io.listen(server);
io.sockets.on('connection', handleNewPeer);
Upon arriving on the html page, the doConnect(isBroadcaster) function is ran from script tag
The doConnect function (In peer.js):
var doConnect = function(isBroadcaster) {
console.log("doConnect");
// broadcaster or normal peer
var user;
if (isBroadcaster)
user = "Broadcaster";
else
user = "Viewer";
(function() {
var pubnub_setup = {
channel: "my_channel",
publish_key: "pub-c-key",
subscribe_key: "sub-c-key",
user: user
};
// Note removed the var
socket = io.connect( 'http://pubsub.pubnub.com', pubnub_setup);
// various socket.on() omitted
})();
Here is what how it was before with just socketIO & it was working:
var doConnect = function(isBroadcaster) {
socket = io.connect();
// various socket.on() omitted
}
My p2p video website is implemented with WebRTC running on a Nodejs + SocketIO server.
I have been trying to incorporate pubnub into it & thought it would be easy since pubnub supports SocketIO (or at least client side?). Really did not think it would be this difficult to set up server side.
Any input at all on this? I think it's something simple that I just cannot put my finger on

Socket.IO on the Server using Node.JS
Socket.IO with PubNub does not provide a Node.JS Socket.IO backend option. However you can use the PubNub SDK directly for on-connect events.
NPM Package
npm install pubnub
After you install the PubNub NPM you can use the node.js server backend:
Node.js Backend Code
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
// PubNub!!! (how to initialize it for use on server)
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
var pubnub = require('pubnub').init({
publish_key : "pub-key",
subscribe_key : "sub-c-key",
uuid : "Server-ID"
});
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
// On user Connect
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
function on_user_connect(data) {
console.log( "User Connected: ", data.uuid );
}
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
// On user Leave
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
function on_user_leave(data) {
console.log( "User Left: ", data.uuid );
}
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
// Open Socket Connection for User Join Events
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
pubnub.subscribe({
channel : 'my_channel',
connect : connected
message : function(message) {
console.log("Message received: ", message);
},
presence : function(data) {
if (data.action == "leave") on_user_leave(data);
if (data.action == "timeout") on_user_leave(data);
if (data.action == "join") on_user_connect(data);
}
});
function connected() {
console.log('connected!');
}

What version of socket.io are you using?
This might not fix it. I am using version 1.+ Have you tried:
io.on('connection', function(socket){
console.log('user connected');
});