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.
IOS CLIENT WITH SOCKET.IO SWIFT:
class SignupViewController: UIViewController{
let socket = SocketIOClient(socketURL: NSURL(string: "http://localhost:3000")!)
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func createUser(sender: AnyObject) {
LoginUser(email: emailInput.text!, password: passwordInput.text!){ results in
self.addHandlers()
self.socket.connect()
}
}
private func addHandlers(){
socket.on("connect") {data, ack in
self.socket.emit("new-device-connect", "ascascasc")
}
}
SERVER:
// start the server if `$ node server.js`
if (require.main === module)
app.io = require('socket.io')(app.start());
//app.start();
app.io.on('connection', function(socket){
console.log("client connected");
socket.on('disconnect', function(){
console.log('user disconnected');
});
});
BROWSER CLIENT
var socket = io('http://localhost:3000');
socket.on('connect', function(){
socket.on("new-device-connect", function(d){
console.log("a new client is connected");
});
socket.on("disconnect", function(){
});
});
When I emit an event in my IOS client name new-device-connect, I need the event to be called on my browser client to show a new IOS device connected, but the browser client isn't receiving the new-device-connect event.
I would put a socket.on("new-device-connect") on your server, I have not done mobile development but I think you are passing that information to your server and not the browser client. Socket.io should then emit your call to the browser correctly.
This is my server side code which has been hosted on IBM Bluemix,
const net = require('net');
const server = net.createServer((c) => { //'connection' listener
console.log('client connected');
c.on('end', () => {
console.log('client disconnected');
});
c.write('hello\r\n');
c.pipe(c);
});
server.listen(8124, () => { //'listening' listener
console.log('server bound');
});
I am using below code as client on local,
var net = require('net');
var HOST = 'xxx.xx.xx.xx';
var PORT = xxxx;
var client = new net.Socket();
client.connect(PORT, HOST, function() {
console.log('CONNECTED TO: ' + HOST + ':' + PORT);
// Write a message to the socket as soon as the client is connected, the server will receive it as message from the client
client.write('I am Chuck Norris!');
});
// Add a 'data' event handler for the client socket
// data is what the server sent to this socket
client.on('data', function(data) {
console.log('DATA: ' + data);
// Close the client socket completely
client.destroy();
});
// Add a 'close' event handler for the client socket
client.on('close', function() {
console.log('Connection closed');
});
When I run, It throws error Like.
events.js:141
throw er; // Unhandled 'error' event
^
Error: connect ETIMEDOUT xxx.xx.xx.xx:xxxx
at Object.exports._errnoException (util.js:856:11)
at exports._exceptionWithHostPort (util.js:879:20)
at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1063:14) vivek#vivek-Latitude-E6220:/var/www/html/test/NODE/net$ node client.js
events.js:141
throw er; // Unhandled 'error' event
^
Error: connect ETIMEDOUT xxxx.xx.xx.xx:xxxx
at Object.exports._errnoException (util.js:856:11)
at exports._exceptionWithHostPort (util.js:879:20)
at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1063:14)
When I run the server code on local, It works perfect. Kindly help me to find the error.
You need to listen on the port that Bluemix assigns for your application. Bluemix will assign your application a port and you will need to bind on that port. Bluemix will load balance to your application and have your application available on ports 443 and 80.
You can get the port with the following code.
var port = process.env.PORT || 8124;
Also you don't need to bind to a host either.
I modified your code below.
const net = require('net');
const server = net.createServer((c) => { //'connection' listener
console.log('client connected');
c.on('end', () => {
console.log('client disconnected');
});
c.write('hello\r\n');
c.pipe(c);
});
var port = process.env.PORT || 8124;
server.listen(port, () => { //'listening' listener
console.log('server bound');
});
The client code tries to connect to the server at the wrong address. Make sure that the client code's IP address and port number match the server's IP address and port number.
Also, ensure that the server is running and that the network connection between the server and the client is open. If the issue persists, try using a different port number and make sure the port is available on the server.
There is a read ECONNRESET Error in your server, when client destroy the socket.
you can catch using
c.on('error', function(err) {
console.log('SOCKET ERROR : ' , err);
});
you can avoid the crash this way.
working version for me, based on your code
server.js
const net = require('net');
var server = net.createServer(function(c) {
console.log('client connected');
c.on('end', function(c) {
console.log('sendHomeKeytoIosDevice : ERROR : ' + c);
});
c.on('error', function(err) {
console.log('sendHomeKeytoIosDevice : ERROR : ' + err);
});
c.write('hello\r\n');
c.pipe(c);
});
server.listen(8124,function() {
console.log('server bound');
});
Client.js
var net = require('net');
var HOST = 'localhost';
var PORT = 8124;
var client = new net.Socket();
client.connect(PORT, HOST, function() {
console.log('CONNECTED TO: ' + HOST + ':' + PORT);
// Write a message to the socket as soon as the client is connected, the server will receive it as message from the client
client.write('I am Chuck Norris!');
});
// Add a 'data' event handler for the client socket
// data is what the server sent to this socket
client.on('data', function(data) {
console.log('DATA: ' + data);
// Close the client socket completely
client.destroy();
});
// Add a 'close' event handler for the client socket
client.on('close', function() {
console.log('Connection closed');
});
My angularjs client websocketserver can properly send to the server, but when sending from server to client, the client doesn't register the event.
I'm using angular-websockets at the client side and ws at my express.js server
Here's my code.
server
var port = process.env.PORT || 3002;
var server = http.createServer(app); // app = express
server.listen(port);
var socketComs = require('./lib/socketcoms').connect(server);
var connect = function(server) {
var wss = new WebSocketServer({
server: server
});
wss.on('connection', function(ws) {
console.log("websocket connection open");
ws.on('message', function incoming(message) {
console.log('received', message); // THIS WORKS FINE
});
var id = setInterval(function() {
ws.send('pong', 'data 123', function(err) {
console.log('sent pong', err); // THIS IS NEVER CAUGHT BY CLIENT, err = clean
});
}, 2000); // Pong is never received
});
};
client
var connect = function() {
ws.$on('$open', function() {
console.log('wow its working');
ws.$emit('message', 'some message');
});
ws.$on('pong', function(data) {
console.log('yes', data);
});
ws.$on('$close', function(data) {
console.log('wss closed');
});
};
Can anyone see what's going wrong?
I'm using ng-websocket with PHP socket, and I have the same issue.
I just opened the ng-websocket.js and..guess what? the "ping" and "pong" events don't exist!
The "incoming" event is called "$message"...
This is how to get data from server:
ws.$on('$message', function (response) {
console.log("DATA FROM SERVER", response);
Installed websocket and socket.io on the server. When I load the browser page, I get this error in the console: Uncaught TypeError: undefined is not a function
(socket.io-1.2.1.js:1)
Here is the server side code:
// Require HTTP module (to start server) and Socket.IO
var http = require('http'), io = require('socket.io');
// Start the server at port 9602
var server = http.createServer(function(req, res){
// Send HTML headers and message
res.writeHead(200,{ 'Content-Type': 'text/html' });
res.end('<h1>Hello Socket Lover!</h1>');
});
server.listen(9602);
// Create a Socket.IO instance, passing it our server
var socket = io.listen(server);
// Add a connect listener
socket.on('connection', function(client){
// Success! Now listen to messages to be received
client.on('message',function(event){
console.log('Received message from client!',event);
});
client.on('disconnect',function(){
clearInterval(interval);
console.log('Server has disconnected');
});
});
And the client side code:
<script src="https://cdn.socket.io/socket.io-1.2.1.js"></script>
<script>
// Create SocketIO instance, connect
var socket = new io.Socket('localhost',{
port: 9602
});
socket.connect();
// Add a connect listener
socket.on('connect',function() {
console.log('Client has connected to the server!');
});
// Add a connect listener
socket.on('message',function(data) {
console.log('Received a message from the server!',data);
});
// Add a disconnect listener
socket.on('disconnect',function() {
console.log('The client has disconnected!');
});
// Sends a message to the server via sockets
function sendMessageToServer(message) {
socket.send(message);
}
</script>
Any help is appreciated.
k4elo
var socket = io("http://127.0.0.1:9000");
// Add a connect listener
socket.on('connect',function() {
console.log('Client has connected to the server!');
});
The above method works with the following cdn
You are creating server on HTTP not HTTPS
<script src='/socket.io/socket.io.js'></script>
instead of script src="https://cdn.socket.io/socket.io-1.2.1.js">