I have the following example of listening to connection and data events, to echo the result back to other telnet clients listening on port 8888. My telnet sessions connect to locahost fine, but no output is echoed. I am hitting my head against a brick wall trying to figure out what is wrong. The execution doesn't even get as far as the 'connect' event.
/server.js
var events = require('events');
var net = require('net');
var channel = new events.EventEmitter();
channel.clients = {};
channel.subscriptions = {};
channel.on('join', function (id, client) {
this.clients[id] = client;
this.subscriptions[id] = function (senderId, message) {
if (id != senderId) {
this.clients[id].write(message);
}
}
this.on('broadcast', this.subscriptions[id]);
});
var server = net.createServer(function (client) {
var id = client.remoteAddress + ':' + client.remotePort;
console.log(id);
client.on('connect', function () {
console.log('A new connection was made');
channel.emit('join', id, client);
});
client.on('data', function (data) {
data = data.toString();
channel.emit('broadcast', id, data);
});
});
server.listen(8888);
I then run in the command line
node server.js
telnet 127.0.0.1 8888
When the callback to net.createServer is called, that's because of an implicit connection event. So your code should look like this:
var server = net.createServer(function (client) {
// when this code is run, the connection has been established
var id = client.remoteAddress + ':' + client.remotePort;
console.log('A new connection was made:', id);
channel.emit('join', id, client);
client.on('data', function(data) {
...
});
client.on('end', function() {
...
});
});
The manual has this to say;
net.createServer([options], [connectionListener])
Creates a new TCP server. The connectionListener argument is automatically set as a listener for the 'connection' event.
In other words, your function (client) { already received the connection event, and adding a listener to it when it has already been dispatched has no further effect.
Related
I'm totally new to the whole nodeJS asynchronous-y callback-y programming so I need more like a guidance to understanding what I'm even doing. With that said, I have two files main.js and server.js
My main file looks like this:
var server=require('./server.js');
server();
function WhenUserClicksButton(){
server();
}
and my server file looks like this:
var net = require('net');
function server(){
net.createServer(function (socket) {
socket.write('\x16'); //SYN character
socket.on('data', function (data) {
//handle data from client
});
}).listen(33333);
}
First call of server(); starts the TCP server. Then function WhenUserClicksButton is called when user clicks button (duhh) in a GUI. But it attempts to start the server again so I get
Error: listen EADDRINUSE :::33333
I got why this is happening but I can't think of a solution for it. What I really need is:
Start the server and listen on 33333
When nothing is happening server and client just exchanges SYN and ACK characters every few seconds (I already have this part done, I just removed it from this example for clarity because it's not really topic of this question)
When user click button change socket.write('\x16'); to socket.write('something');
Then wait for server and client to exchange data and after everything is done return results back to main.js
As I said, I'm new to this and I believe my problem lies in not understanding fully of what I'm doing. Any help and explanations are welcome!
I think you're very near where you need to be. I would do something like this:
server.js
var net = require('net');
var netServer = null;
var netSocket = null;
function sendData(data) {
if (netServer && netSocket) {
console.log('Send data: sending: ', data);
netSocket.write(data);
}
}
function startServer(){
netServer = net.createServer(function (socket) {
netSocket = socket;
socket.write('\x16'); //SYN character
socket.on('data', function (data) {
console.log('Server: data from client: ', data);
if (data.length === 1 && data[0] === 0x16) {
// log and ignore SYN chars..
console.log('SYN received from client');
} else if (newDataCallback) {
newDataCallback(data);
};
});
});
console.log('Server listening on 33333..');
netServer.listen(33333);
}
var newDataCallback = null;
function setNewDataCallback(callback) {
newDataCallback = callback;
}
module.exports = {
sendData: sendData,
startServer: startServer,
setNewDataCallback: setNewDataCallback
};
main.js
var server = require('./server');
function newDataCallback(data) {
console.log('newDataCallback: New data from server: ', data);
}
server.setNewDataCallback(newDataCallback);
server.startServer();
function wheneverUserClicksButton() {
server.sendData('something');
}
testClient.js
var clientSocket = net.createConnection(33333, "127.0.0.1");
clientSocket.on('data', (someData) => {
console.log('Data received', someData);
});
clientSocket.on('connect', () => {
console.log('Client Socket connected ');
clientSocket.write('Hello from client');
});
This question already has answers here:
socket.emit in a simple TCP Server written in NodeJS?
(3 answers)
Closed 5 years ago.
I am new to NodeJS and started to learn by building a simple command line chat application. I have the following code for Server and Client. Client-Server communication is successful but I am not able to capture 'adduser' event from the client. Please tell me where I am going wrong.
Server:
var net = require('net');
var chatServer = net.createServer(function(socket){
socket.pipe(socket);
}),
userName="";
chatServer.on('connection',function(client){
console.log("ChatterBox Server\n");
client.write("Welcome to ChatterBox!\n");
client.on('data',function(data){
console.log(""+data);
});
client.on('adduser',function(n){
console.log("UserName: "+ n);
userName = n;
});
});
chatServer.listen(2708);
Client:
var net = require('net');
var client = new net.Socket();
client.connect(2708,'127.0.0.1');
client.on('connect',function(){
client.emit('adduser',"UserName");
});
console.log("Client Connected!\n");
client.on('data',function(data){
console.log(""+data);
});
I guess you don't have to do from the client side :
client.connect(2708,'127.0.0.1');
Just write your client like this is sufficient.
var net = require('net');
var client = new net.Socket();
client.connect(2708, '127.0.0.1',function(){
console.log("Client Connected!\n");
client.emit('adduser',"UserName");
});
client.on('data',function(data){
console.log(""+data);
});
client.on('close', function() {
console.log('Connection closed');
});
So the server side :
var net = require('net');
var sockets = [];
var port = 2708;
var guestId = 0;
var server = net.createServer(function(socket) {
// Increment
guestId++;
socket.nickname = "Guest" + guestId;
var userName = socket.nickname;
sockets.push(socket);
// Log it to the server output
console.log(userName + ' joined this chat.');
// Welcome user to the socket
socket.write("Welcome to telnet chat!\n");
// Broadcast to others excluding this socket
broadcast(userName, userName + ' joined this chat.\n');
socket.on('adduser',function(n){
console.log("UserName: "+ n);
userName = n;
});
// When client sends data
socket.on('data', function(data) {
var message = clientName + '> ' + data.toString();
broadcast(clientName, message);
// Log it to the server output
process.stdout.write(message);
});
// When client leaves
socket.on('end', function() {
var message = clientName + ' left this chat\n';
// Log it to the server output
process.stdout.write(message);
// Remove client from socket array
removeSocket(socket);
// Notify all clients
broadcast(clientName, message);
});
// When socket gets errors
socket.on('error', function(error) {
console.log('Socket got problems: ', error.message);
});
});
// Broadcast to others, excluding the sender
function broadcast(from, message) {
// If there are no sockets, then don't broadcast any messages
if (sockets.length === 0) {
process.stdout.write('Everyone left the chat');
return;
}
// If there are clients remaining then broadcast message
sockets.forEach(function(socket, index, array){
// Dont send any messages to the sender
if(socket.nickname === from) return;
socket.write(message);
});
};
// Remove disconnected client from sockets array
function removeSocket(socket) {
sockets.splice(sockets.indexOf(socket), 1);
};
// Listening for any problems with the server
server.on('error', function(error) {
console.log("So we got problems!", error.message);
});
// Listen for a port to telnet to
// then in the terminal just run 'telnet localhost [port]'
server.listen(port, function() {
console.log("Server listening at http://localhost:" + port);
});
So you've got an object "users" inside the "user" when is connected, push user to the array users but you need to do (server side) on('close', ... to remove the user from users when connected is false ... etc
I am using socket.io for private chatting for the server side I am using
socket.broadcast.to(receiver_socket_id).emit('message', data); // where data is a json object containing text
And at the client side code I catch the data using
socket.on('message', function (data) {
alert(data. text);
});
Its working properly and showing the alert on that specific user (socket id) ‘s panel when only two socket are connected (sender and receiver). But the problem appears when one more user connects to that socket then I see two alerts and when total 4 user connected (sender + receiver + two others) then see 3 alerts. But the good point is I can see the alerts only that specific client's panel not the others.
I can’t understand the problem, please help.
Please have a look on it
gyazo.com/a98d3a64a9fc6487e6ded8ccd90fd5ab
it prints test three times because three browsers are opened.
Full code here:
Sever side (I have used Redis):
var app = require('express')();
var server = require('http').Server(app);
var io = require('socket.io')(server);
var redis = require('redis');
server.listen(8080);
var usernames = {};
io.on('connection', function (socket) {
console.log(socket.id);
socket.on('adduser', function (userId) {
usernames[userId] = socket.id;
});
var redisClient = redis.createClient();
redisClient.subscribe('message-channel');
redisClient.on('message', function (channel, data) {
var jsonObj = JSON.parse(data);
var rcvrId = jsonObj.rcvrId;
socket.broadcast.to(usernames[rcvrId]).emit('message', data); // Not throwing error....should work
});
socket.on('disconnect', function () {
console.log(socket.id + ' Disconnected');
redisClient.quit();
});
});
Client side:
var socket = io.connect('http://localhost:8080');
var userId = $('input[name="userId"]').val();
var rcvrId = $('input[name="rcvrId"]').val();
socket.on('connect', function () {
// call the server-side function 'adduser' and send one parameter (value of prompt)
socket.emit('adduser', userId);
});
socket.on('message', function (data) {
data = jQuery.parseJSON(data);
console.log(data);
$("#messages").append("<div><strong>" + data.userId + " : </strong><span>" + data.message + "</span></div>");
});
You can use io.of('/').sockets[rcvrId].emit('message', data). In case you are using a different namespace just replace the / with your namespace.
I have the following situation and just wanted to check if I am doing it right. I have a couple of devices at my customers (RS232). Now I have a RS232-WIFI dongle connected with it, so data out of the device is sent over to my server (it outputs a datastring, example: {12,1,etc). On my server I have a NodeJS script running, that opens up a port and fetches all data coming in.
var net = require('net');
var host = '1.1.1.1';
var servers = [];
var ports = [20000, 20001, 20002, 20003, 20004];
// Create servers
ports.forEach(function (port) {
var s = net.createServer(function (sock) {
// We have a connection - a socket object is assigned to the connection automatically
console.log('CONNECTED (' + sock.localPort + '): ' + sock.remoteAddress + ':' + sock.remotePort);
// Add a 'data' event handler to this instance of socket
sock.on('data', function (data) {
// post data to a server so it can be saved and stuff
postData(data.toString(), sock);
// close connection
sock.end();
});
sock.on('error', function (error) {
console.log('******* ERROR ' + error + ' *******');
// close connection
sock.end();
});
});
s.listen(port, host, function () {
console.log('Server listening on ' + host + ':' + s.address().port);
});
servers.push(s);
});
Okay, so this works pretty good. But I am wondering, sometimes not all of the data is posted at once, sometimes I get {12, and after a second I get the rest (or even more times is needed). What can I do to optimize this script further? Do I need to call sock.end(); after receiving data? Does this hurt network performance for me or my customers?
If you guys need more info let me know.
That depends on the protocol of your devices, if the devices use each connection for a chunk of data, you can write the program like so: (Do not close the socket on data event)
....
// socket will close and destroy automatically after the device close the connection
var s = net.createServer(function (sock) {
sock.setEncoding('utf8');
var body = "";
sock.on('data', function (data) {
body = body + data;
});
sock.on('end', function() {
console.log(data);
postData(data);
});
// TODO error handling here
});
....
Note: Socket is not guaranteed to give you all data at once, you should listen data event then concat all chunks before using.
If your devices don't close socket, you will not receive on('end'), then the code should be like this:
....
var s = net.createServer(function (sock) {
sock.setEncoding('utf8');
// var body = "";
sock.on('data', function (data) {
// body = body + data;
postData(data);
});
sock.on('end', function() {
console.log('end');
});
// TODO error handling here
});
....
I have two questions:
1) How can I get the IP address, and any other possible data about the client when it connects (see comment in code in the connect section)
2) Will this code safely allow multiple client connections at the same time?
var net = require('net');
var sys = require('sys');
var server = net.createServer(function (stream) {
stream.setEncoding('utf8');
stream.on('connect', function() {
///////////////////////////////////////////////////////
console.log("WANT THE IP OF THE CONNECTOR HERE!!!!!!");
///////////////////////////////////////////////////////
});
// data recieve
stream.on('data', function (data) {
//stream.write(data);
console.log("recv: [" + data + "]");
});
// end connection
stream.on('end', function () {
stream.end();
});
});
server.listen(50505, 'localhost');
http://nodejs.org/docs/v0.3.2/api/net.html#stream.remoteAddress
Yes