I have Apache running on Windows 7 Pro. I installed Apache using XAMPP bundle.
I need to call an API once every second. To do that, I created a SharedWorker who calls the API every second using XMLHttpRequest
However, I am running into an issue where the web server Apache hits it's max TCP connection allowed. Of course I can increase the allowed TCP connections on the server, but that does not solve my problem it only patches it until the server gets busy and overloaded.
After troubleshooting the TCP problem, it become clear to me that the XMLHttpRequest is not reusing an existing TCP connection. It opens a new TCP connection with every request/every second. I expect to have 1 TCP connection to be utilized to handle my XMLHttpRequest connection.
While I was the only user is connection to the website on the server, I launched TCPView on the web server to watch the tcp connections. I started out with 30 TCP connection with a state of TIME_WAIT. Every second later, one more connection was created until it reached about 122-130 and then it stopped. Now the server seems to be recycling the connections every 60 seconds, but still generating a new TCP connection for every XMLHttpRequest every second.
I also understand that each time a page is loaded the client/browser could create multiple TCP connection for various of reasons. But, I am expecting to have 1 TCP connection to handle my XMLHttpRequest and resuse that connection over and over.
I know some may suggest using WebSockets or Server-Sent-Events, but in my case I can't. I must keep my ShardWorker implementation.
Question
What can I do to make the XMLHttpRequest reuse of an open TCP connection?
Below is my ShardWorker implementation i.e. worker.js
var clients = new Array();
var xhr = null;
//runs only when a new connection starts
onconnect = function(event) {
var port = event.ports[0];
clients.push(port);
port.start();
//implement a channel for a communication between the connecter and the SharedWorker
port.addEventListener("message",
function(event) {
replyToClientMessage(event, port);
} , false
);
}
//reply to any message sent to the SharedWorker with the same message but add the phrase "SharedWorker Said: " to it
replyToClientMessage = function (event, port) {
port.postMessage("Worker Replied With: " + event.data);
}
//check all open clients and post a message to each
function notifyAllPorts(msg){
var len = clients.length;
var port;
for(i = 0; i < len; i++) {
port = clients[i];
port.postMessage(msg);
}
}
function checkQueue(cb) {
//create a new XMLHttpRequest only once
if (xhr == null) {
xhr = new XMLHttpRequest();
xhr.addEventListener("loadend", cb);
xhr.addEventListener("load", handlerMessageReceived);
}
xhr.open('GET', '/add-ons/icws/push.php', true);
xhr.send();
}
//handler a sucessfull request
function handlerMessageReceived()
{
var queue = JSON.parse(this.responseText);
notifyAllPorts(queue);
}
var promise = Promise.resolve(true);
setInterval(function () {
promise = promise.then(function () {
return new Promise(function (resolve) {
checkQueue(resolve);
});
});
}, 1000);
Here is how I put Sharedworker to work
//establish connection to the shared worker
var worker = new SharedWorker("/add-ons/icws/js/worker.js" );
//listen for a message send from the worker
worker.port.addEventListener("message",
function(event) {
console.log(event.data);
processServerData(event.data);
}
, false
);
worker.onerror = function(event){
console.log(event);
};
//start the connection to the shared worker
worker.port.start();
Related
Is it possible to terminate a websocket connection from server without closing the entire server? If it is then, how can I achieve it?
Note: I'm using NodeJS as back-end and 'ws' websocket module.
So because of some sort of omission in the documentation regarding ws.close() and ws.terminate() I think the solutions in provided answers won't close the sockets gracefully in some cases, thus keeping them hanging in the Event Loop.
Compare the next two methods of ws package:
ws.close():
Initializes close handshake, sending close frame to the peer and awaiting to receive close frame from the peer, after that sending FIN packet in attempt to perform a clean socket close. When answer received, the socket is destroyed. However, there is a closeTimeout that will destroy socket only as a worst case scenario, and it potentially could keep socket for additional 30 seconds, preventing the graceful exit with your custom timeout:
// ws/lib/WebSocket.js:21
const closeTimeout = 30 * 1000; // Allow 30 seconds to terminate the connection cleanly.
ws.terminate():
Forcibly destroys the socket without closing frames or fin packets exchange, and does it instantly, without any timeout.
Hard shutdown
Considering all of the above, the "hard landing" scenario would be as follows:
wss.clients.forEach((socket) => {
// Soft close
socket.close();
process.nextTick(() => {
if ([socket.OPEN, socket.CLOSING].includes(socket.readyState)) {
// Socket still hangs, hard close
socket.terminate();
}
});
});
Soft shutdown
You can give your clients some time to respond, if you could allow yourself to wait for a while (but not 30 seconds):
// First sweep, soft close
wss.clients.forEach((socket) => {
socket.close();
});
setTimeout(() => {
// Second sweep, hard close
// for everyone who's left
wss.clients.forEach((socket) => {
if ([socket.OPEN, socket.CLOSING].includes(socket.readyState)) {
socket.terminate();
}
});
}, 10000);
Important: proper execution of close() method will emit 1000 close code for close event, while terminate() will signal abnormal close with 1006 (MDN WebSocket Close event).
If you want to kick ALL clients without closing the server you can do this:
for(const client of wss.clients)
{
client.close();
}
you can also filter wss.clients too if you want to look for one in particular. If you want to kick a client as part of the connection logic (i.e. it sends bad data etc), you can do this:
let WebSocketServer = require("ws").Server;
let wss = new WebSocketServer ({ port: 8080 });
wss.on('connection', function connection(ws) {
ws.send('something');
ws.close(); // <- this closes the connection from the server
});
and with a basic client
"use strict";
const WebSocket = require("ws");
let ws = new WebSocket("ws://localhost:8080");
ws.onopen = () => {
console.log("opened");
};
ws.onmessage = (m) => {
console.log(m.data);
};
ws.onclose = () => {
console.log("closed");
};
you'll get:
d:/example/node client
opened
something
closed
According to the ws documentation, you need to call websocket.close() to terminate a connection.
let server = new WebSocketServer(options);
server.on('connection', ws => {
ws.close(); //terminate this connection
});
Just use ws.close() in this way.
var socketServer = new WebSocketServer();
socketServer.on('connection', function (ws) {
ws.close(); //Close connecton for connected client ws
});
If you use var client = net.createConnection() to create the socket you can use client.destroy() to destroy it.
With ws it should be:
var server = new WebSocketServer();
server.on('connection', function (socket) {
// Do something and then
socket.close(); //quit this connection
});
I am trying to create a system where I have a desktop client created in VB, and a browser based client, that can send messages to each other. I am using a Node.js server to handle the connections and messages.
This is the code of my Node.js server:
net = require('net')
// Supports multiple client chat application
// Keep a pool of sockets ready for everyone
// Avoid dead sockets by responding to the 'end' event
var sockets = [];
// Create a TCP socket listener
var s = net.Server(function (socket) {
// Add the new client socket connection to the array of
// sockets
sockets.push(socket);
// 'data' is an event that means that a message was just sent by the
// client application
socket.on('data', function (msg_sent) {
// Loop through all of our sockets and send the data
for (var i = 0; i < sockets.length; i++) {
// Don't send the data back to the original sender
if (sockets[i] == socket) // don't send the message to yourself
continue;
// Write the msg sent by chat client
sockets[i].write(msg_sent);
}
});
// Use splice to get rid of the socket that is ending.
// The 'end' event means tcp client has disconnected.
socket.on('end', function () {
var i = sockets.indexOf(socket);
sockets.splice(i, 1);
});
});
s.listen(8000);
console.log('System waiting at http://localhost:8000');
With this sever, I am able to send messages between two desktop clients successfully.
However, because I am using net and not HTTP I cannot get the browser based client to connect.
How can I get both the clients to connect? I would really appreciate any help/suggestions/directions. I have been searching everywhere for about 4 days now! TIA!
You could use http or express for browser based client. could check socket.io also which works on http port.
I would try to help more if know type of the desktop client you are using.
I'm trying to develop a video-chat application using webRTC and WebSockets for signaling.
My problem is that I don't know exactly what is the process of creating RTCPeerConnection and connect both peers(2 browsers) through webSocket(Locally at least).
I know how to communicate clients though WebSockets, but not with the RTCPeerConnection API, you know any tutorial step-by-step explaining the process?(Offer SDP, answers, ICE, ...) and, on the other hand, how looks the server code to managing these clients through RTCPeerConnection?
Here is my Node.js code for the server
"use strict";
// Optional. You will see this name in eg. 'ps' or 'top' command
process.title = 'node-webrtc';
// Port where we'll run the websocket server
var webSocketsServerPort = 1337;
// websocket and http servers
var webSocketServer = require('websocket').server;
var http = require('http');
/* ---------------------------------
GLOBAL VARIABLES
----------------------------------*/
// latest 100 messages
//var history = [ ];
// list of currently connected clients (users)
var clients = [ ];
/* ---------------------------------
HTTP SERVER
----------------------------------*/
var server = http.createServer(function(request, response) {
// Not important for us. We're writing WebSocket server, not HTTP server
});
server.listen(webSocketsServerPort, function() {
console.log((new Date()) + " Server is listening on port " + webSocketsServerPort);
});
/* ---------------------------------
WEBSOCKET SERVER
----------------------------------*/
var wsServer = new webSocketServer({
// WebSocket server is tied to a HTTP server. WebSocket request is just
// an enhanced HTTP request. For more info http://tools.ietf.org/html/rfc6455#page-6
httpServer: server
});
// This callback function is called every time someone
// tries to connect to the WebSocket server
wsServer.on('request', function(request) {
console.log((new Date()) + ' Connection from origin ' + request.origin + '.');
// accept connection - you should check 'request.origin' to make sure that
// client is connecting from your website
// (http://en.wikipedia.org/wiki/Same_origin_policy)
var connection = request.accept(null, request.origin);
// we need to know client index to remove them on 'close' event
var index = clients.push(connection) - 1;
console.log((new Date()) + ' Connection accepted.');
// user sent some message
connection.on('message', function(message) {
for (var i=0; i < clients.length; i++) {
clients[i].sendUTF(message);
}
});
// user disconnected
connection.on('close', function(conn) {
console.log((new Date()) + " Peer " + conn.remoteAddress + " disconnected.");
// remove user from the list of connected clients
clients.splice(index, 1);
});
});
You might want to have a look at the codelab I did for Google I/O: bitbucket.org/webrtc/codelab.
Step 5 shows how to set up a signaling server using socket.io, and Step 6 puts this together with RTCPeerConnection to make a simple video chat app.
You might also want to have a look at easyRTC (full stack) and Signalmaster (signaling server created for SimpleWebRTC).
The 'canonical' WebRTC video chat example at apprtc.appspot.com uses XHR and the Google App Engine Channel API for signaling.
Have you looked at or come across WebRTC.io? It is an opensource GitHub project that utilizes Node.js and websockets to do the exact thing you are talking about. I, not being much of a javascript person, was able to figure out what it was doing within a week. It isn't a step by step instruction, but anyone with javascript experience would be able to figure out the function call order.
There are two bits to the code: the server side and the client side. The server side is run with Node.js, and serves up the client side code to the browser. If I remember correctly, since the two projects are separate, if you want to combine them you will have to copy the webrtcio.js file from the client side and paste it into the server side folder. Although, I think if you clone the github repository right, you might not have to worry about that.
I'm trying to learn how to create an RTCPeerConnection so that I can use the DataChannel API. Here's what I have tried from what I understood:
var client = new mozRTCPeerConnection;
var server = new mozRTCPeerConnection;
client.createOffer(function (description) {
client.setLocalDescription(description);
server.setRemoteDescription(description);
server.createAnswer(function (description) {
server.setLocalDescription(description);
client.setRemoteDescription(description);
var clientChannel = client.createDataChannel("chat");
var serverChannel = server.createDataChannel("chat");
clientChannel.onmessage = serverChannel.onmessage = onmessage;
clientChannel.send("Hello Server!");
serverChannel.send("Hello Client!");
function onmessage(event) {
alert(event.data);
}
});
});
I'm not sure what's going wrong, but I'm assuming that the connection is never established because no messages are being displayed.
Where do I learn more about this? I've already read the Getting Started with WebRTC - HTML5 Rocks tutorial.
I finally got it to work after sifting through a lot of articles: http://jsfiddle.net/LcQzV/
First we create the peer connections:
var media = {};
media.fake = media.audio = true;
var client = new mozRTCPeerConnection;
var server = new mozRTCPeerConnection;
When the client connects to the server it must open a data channel:
client.onconnection = function () {
var channel = client.createDataChannel("chat", {});
channel.onmessage = function (event) {
alert("Server: " + event.data);
};
channel.onopen = function () {
channel.send("Hello Server!");
};
};
When the client creates a data channel the server may respond:
server.ondatachannel = function (channel) {
channel.onmessage = function (event) {
alert("Client: " + event.data);
};
channel.onopen = function () {
channel.send("Hello Client!");
};
};
We need to add a fake audio stream to the client and the server to establish a connection:
navigator.mozGetUserMedia(media, callback, errback);
function callback(fakeAudio) {
server.addStream(fakeAudio);
client.addStream(fakeAudio);
client.createOffer(offer);
}
function errback(error) {
alert(error);
}
The client creates an offer:
function offer(description) {
client.setLocalDescription(description, function () {
server.setRemoteDescription(description, function () {
server.createAnswer(answer);
});
});
}
The server accepts the offer and establishes a connection:
function answer(description) {
server.setLocalDescription(description, function () {
client.setRemoteDescription(description, function () {
var port1 = Date.now();
var port2 = port1 + 1;
client.connectDataConnection(port1, port2);
server.connectDataConnection(port2, port1);
});
});
}
Phew. That took a while to understand.
I've posted a gist that shows setting up a data connection, compatible with both Chrome and Firefox.
The main difference is that where in FF you have to wait until the connection is set up, in Chrome it's just the opposite: it seems you need to create the data connection before any offers are sent back/forth:
var pc1 = new RTCPeerConnection(cfg, con);
if (!pc1.connectDataConnection) setupDC1(); // Chrome...Firefox defers per other answer
The other difference is that Chrome passes an event object to .ondatachannel whereas FF passes just a raw channel:
pc2.ondatachannel = function (e) {
var datachannel = e.channel || e;
Note that you currently need Chrome Nightly started with --enable-data-channels for it to work as well.
Here is a sequence of events I have working today (Feb 2014) in Chrome. This is for a simplified case where peer 1 will stream video to peer 2.
Set up some way for the peers to exchange messages. (The variance in how people accomplish this is what makes different WebRTC code samples so incommensurable, sadly. But mentally, and in your code organization, try to separate this logic out from the rest.)
On each side, set up message handlers for the important signalling messages. You can set them up and leave them up. There are 3 core messages to handle & send:
an ice candidate sent from the other side ==> call addIceCandidate with it
an offer message ==> SetRemoteDescription with it, then make an answer & send it
an answer message ===> SetRemoteDescription with it
On each side, create a new peerconnection object and attach event handlers to it for important events: onicecandidate, onremovestream, onaddstream, etc.
ice candidate ===> send it to other side
stream added ===> attach it to a video element so you can see it
When both peers are present and all the handlers are in place, peer 1 gets a trigger message of some kind to start video capture (using the getUserMedia call)
Once getUserMedia succeeds, we have a stream. Call addStream on the peer 1's peer connection object.
Then -- and only then -- peer 1 makes an offer
Due to the handlers we set up in step 2, peer 2 gets this and sends an answer
Concurrently with this (and somewhat obscurely), the peer connection object starts producing ice candidates. They get sent back and forth between the two peers and handled (steps 2 & 3 above)
Streaming starts by itself, opaquely, as a result of 2 conditions:
offer/answer exchange
ice candidates received, exchanged, and added
I haven't found a way to add video after step 9. When I want to change something, I go back to step 3.
I'm using the ws library for WebSockets in Node.js and
I'm trying this example from the library examples:
var sys = require("sys"),
ws = require("./ws");
ws.createServer(function (websocket) {
websocket.addListener("connect", function (resource) {
// emitted after handshake
sys.debug("connect: " + resource);
// server closes connection after 10s, will also get "close" event
setTimeout(websocket.end, 10 * 1000);
}).addListener("data", function (data) {
// handle incoming data
sys.debug(data);
// send data to client
websocket.write("Thanks!");
}).addListener("close", function () {
// emitted when server or client closes connection
sys.debug("close");
});
}).listen(8080);
All OK. It works, but running 3 clients, for instance, and sending "Hello!" from one will make the server only reply "Thanks!" to the client which sent the message, not to all.
How can I broadcast "Thanks!" to all connected clients when someone sends "Hello!"?
Thanks!
If you want to send out to all clients, you have to keep track of them. Here is a sample:
var sys = require("sys"),
ws = require("./ws");
// # Keep track of all our clients
var clients = [];
ws.createServer(function (websocket) {
websocket.addListener("connect", function (resource) {
// emitted after handshake
sys.debug("connect: " + resource);
// # Add to our list of clients
clients.push(websocket);
// server closes connection after 10s, will also get "close" event
// setTimeout(websocket.end, 10 * 1000);
}).addListener("data", function (data) {
// handle incoming data
sys.debug(data);
// send data to client
// # Write out to all our clients
for(var i = 0; i < clients.length; i++) {
clients[i].write("Thanks!");
}
}).addListener("close", function () {
// emitted when server or client closes connection
sys.debug("close");
for(var i = 0; i < clients.length; i++) {
// # Remove from our connections list so we don't send
// # to a dead socket
if(clients[i] == websocket) {
clients.splice(i);
break;
}
}
});
}).listen(8080);
I was able to get it to broadcast to all clients, but it's not heavily tested for all cases. The general concept should get you started though.
EDIT: By the way I'm not sure what the 10 second close is for so I've commented it out. It's rather useless if you're trying to broadcast to all clients since they'll just keep getting disconnected.
I would recommend you to use socket.io. It has example web-chat functionality out of the box and also provides abstraction layer from the socket technology on client (WebSockets are supported by Safari, Chrome, Opera and Firefox, but disabled in Firefox and Opera now due to security vulnerabilities in ws-protocol).