I was going to use PaperCut API though as far as I can judge XML-RPC doesn't support Node.JS or I couldn't find an appropriate client for the purpose. Here's the link with PaperCut API:
https://www.papercut.com/support/resources/manuals/ng-mf/common/topics/tools-web-services.html
I was wondering who had been able to get it working in JavaScript. I'm using Node.js in QNAP (in Container Station). If it can be run in Python should I install Python container? Could I use a snippet of code in Python requesting it from Node.js?
I work for PaperCut Software
Sorry it took me so long to reply to this, but I eventually found a free afternoon to knock up some code.
var xmlrpc = require('xmlrpc')
const authToken = 'token'
const hostAddress = "172.24.96.1"
// Waits briefly to give the XML-RPC server time to start up and start
// listening
setTimeout(function () {
// Creates an XML-RPC client. Passes the host information on where to
// make the XML-RPC calls.
var client = xmlrpc.createClient({ host: hostAddress, port: 9191, path: '/rpc/api/xmlrpc'})
// Sends a method call to the PaperCut MF/NG server
client.methodCall(`api.${process.argv[2]}`, [authToken].concat(process.argv.slice(3)), function (error, value) {
// Results of the method response
if (undefined === error || null === error) {
console.log(`Method response for \'${process.argv[2]}\': ${value}`)
}
else
{
console.log(`Error response for \'${process.argv[2]}\': ${error}`)
}
})
}, 1000)
To run this from the command line try something like
node main.js getUserProperty alec balance
I am pretty new to node.js. I am working on an app able to display NFC content on a webpage. I am using nfc-pcsp package (https://github.com/pokusew/nfc-pcsc), I can easily read data on server side. Now I just would like to display the data in the webpage, but I am stuck on the logic. Here is a part of my server code:
// ### launch server for client
var http = require('http');
var html = require('fs').readFileSync(__dirname+'/custom.html');
var server = require('http').createServer(function(req, res){
res.end(html);
});
server.listen(3000, '127.0.0.1');
console.log('Server running at http://127.0.0.1:3000/');
//######
//#launch NFC routine ######
const nfc = new NFC(); // const nfc = new NFC(minilogger); // optionally you can pass logger to see internal debug logs
let readers = [];
nfc.on('reader', async reader => {
pretty.info(`device attached`, { reader: reader.name });
// the event is correctly displayed in the console. How to update html here?
readers.push(reader);
nfc.on('error', err => {
pretty.error(`an error occurred`, err);
});
It seems to me that I need a res object to update the html page, but as I do not get any request from client, how do I update the page just based on the callback from NFC module reader? Hope my question is clear.
Thanks,
Matt
I suggest you to use the express API
command with npm CLI : npm install --save express at your root project folder in your terminal
Then, you will be able to create a route in Get, Post, Put or Delete.
Next, In your client side you will be able to call this route by a get, post or whatever with a promise, ajax request whatever you want :)
Just understand that in order to receive or send data to your server, you need an url and with Express, you can create your own url.
https://www.npmjs.com/package/express
Don't hesitate to have a look on this API, and i'm pretty sure you will find the answer to your question on your own :)
I am using Node.js to connect to a server using gRPC that performs a long running task.
The server sends a unidirectional stream to the client (the Node.js app) while the job is in progress. I need to implement a Stop button and am told that closing the gRPC stream will stop the job in progress.
This is currently my code:
let express = require('express'),
router = express.Router(),
grpc = require('grpc'),
srv = grpc.load(__dirname + '/job_handler.proto').ns;
let startJob = (jobID, parameters) => srv.createJob(jobID, parameters);
router.post('/jobs', (req, res) => {
let lengthyOperation = startJob(jobID, parameters);
lengthyOperation.on('data', (data) => {
console.log(`Data from lengthy operation: ${data}`);
});
lengthyOperation.on('end', () =>
console.log('Lengthy operation completed');
});
res.setHeader('Location', `/jobs/${jobID}`);
res.status(202).send();
});
As you can see, I send an HTTP 202 response to the client upon creating the job and it continues asynchronously in the background.
Questions:
How do I close the stream?
How do I access the lengthyOperation variable to do so?
The lengthyOperation object has a cancel method that cancels the call. So, when you want to stop the stream, just call lengthyOperation.cancel().
Note that when you do this, it will cause the call to end with an error. I would recommend adding a lengthyOperation.on('error', ...) handler to handle that error.
Is there a way to close a response? I can use res.end() but it doesn't actually close the socket.
What I want to achieve: I am writing a Java program which interfaces with the network, and I am writing a NodeJS server for this. Java code:
String line;
while((line = in.readLine()) != null) {
System.out.println("RES: "+line);
}
But this just keeps hanging. No end connection, still waiting for input from the socket.
Node:
exports.getAll = function (req, res) {
res.set("Content-Type", "text/plain");
res.set(200);
res.send(..data..);
res.end();
}
however res.end() does not close the connection. As said before, Java keeps thinking there will be something next so it is stuck in the while loop.
Solved by setting a HTTP header to close the connection instead of default keep-alive strategy.
res.set("Connection", "close");
In case someone who really wants just to close the connection finds this, you can use res.socket or res.connection to get the net.Socket object which comes with a destroy method:
res.connection.destroy();
I'm working with socket.io and node.js and until now it seems pretty good, but I don't know how to send a message from the server to an specific client, something like this:
client.send(message, receiverSessionId)
But neither the .send() nor the .broadcast() methods seem to supply my need.
What I have found as a possible solution, is that the .broadcast() method accepts as a second parameter an array of SessionIds to which not send the message, so I could pass an array with all the SessionIds connected at that moment to the server, except the one I wish send the message, but I feel there must be a better solution.
Any ideas?
Ivo Wetzel's answer doesn't seem to be valid in Socket.io 0.9 anymore.
In short you must now save the socket.id and use io.sockets.socket(savedSocketId).emit(...) to send messages to it.
This is how I got this working in clustered Node.js server:
First you need to set Redis store as the store so that messages can go cross processes:
var express = require("express");
var redis = require("redis");
var sio = require("socket.io");
var client = redis.createClient()
var app = express.createServer();
var io = sio.listen(app);
io.set("store", new sio.RedisStore);
// In this example we have one master client socket
// that receives messages from others.
io.sockets.on('connection', function(socket) {
// Promote this socket as master
socket.on("I'm the master", function() {
// Save the socket id to Redis so that all processes can access it.
client.set("mastersocket", socket.id, function(err) {
if (err) throw err;
console.log("Master socket is now" + socket.id);
});
});
socket.on("message to master", function(msg) {
// Fetch the socket id from Redis
client.get("mastersocket", function(err, socketId) {
if (err) throw err;
io.sockets.socket(socketId).emit(msg);
});
});
});
I omitted the clustering code here, because it makes this more cluttered, but it's trivial to add. Just add everything to the worker code. More docs here http://nodejs.org/api/cluster.html
each socket joins a room with a socket id for a name, so you can just
io.to('socket#id').emit('hey')
docs: http://socket.io/docs/rooms-and-namespaces/#default-room
The simplest, most elegant way
verified working with socket.io v3.1.1
It's as easy as:
client.emit("your message");
And that's it. Ok, but how does it work?
Minimal working example
Here's an example of a simple client-server interaction where each client regularly receives a message containing a sequence number. There is a unique sequence for each client and that's where the "I need to send a message to a particular client" comes into play.
Server
server.js
const
{Server} = require("socket.io"),
server = new Server(8000);
let
sequenceNumberByClient = new Map();
// event fired every time a new client connects:
server.on("connection", (socket) => {
console.info(`Client connected [id=${socket.id}]`);
// initialize this client's sequence number
sequenceNumberByClient.set(socket, 1);
// when socket disconnects, remove it from the list:
socket.on("disconnect", () => {
sequenceNumberByClient.delete(socket);
console.info(`Client gone [id=${socket.id}]`);
});
});
// sends each client its current sequence number
setInterval(() => {
for (const [client, sequenceNumber] of sequenceNumberByClient.entries()) {
client.emit("seq-num", sequenceNumber);
sequenceNumberByClient.set(client, sequenceNumber + 1);
}
}, 1000);
The server starts listening on port 8000 for incoming connections. As soon as a new connection is established, that client is added to a map that keeps track of its sequence number. The server also listens for the disconnect event to remove the client from the map when it leaves.
Each and every second, a timer is fired. When it does, the server walks through the map and sends a message to every client with their current sequence number, incrementing it right after. That's all that is to it. Easy peasy.
Client
The client part is even simpler. It just connects to the server and listens for the seq-num message, printing it to the console every time it arrives.
client.js
const
io = require("socket.io-client"),
ioClient = io.connect("http://localhost:8000");
ioClient.on("seq-num", (msg) => console.info(msg));
Running the example
Install the required libraries:
npm install socket.io#3.1.1 socket.io-client#3.1.1
Run the server:
node server
Open other terminal windows and spawn as many clients as you want by running:
node client
I have also prepared a gist with the full code here.
Well you have to grab the client for that (surprise), you can either go the simple way:
var io = io.listen(server);
io.clients[sessionID].send()
Which may break, I doubt it, but it's always a possibility that io.clients might get changed, so use the above with caution
Or you keep track of the clients yourself, therefore you add them to your own clients object in the connection listener and remove them in the disconnect listener.
I would use the latter one, since depending on your application you might want to have more state on the clients anyway, so something like clients[id] = {conn: clientConnect, data: {...}} might do the job.
You can use
//send message only to sender-client
socket.emit('message', 'check this');
//or you can send to all listeners including the sender
io.emit('message', 'check this');
//send to all listeners except the sender
socket.broadcast.emit('message', 'this is a message');
//or you can send it to a room
socket.broadcast.to('chatroom').emit('message', 'this is the message to all');
In 1.0 you should use:
io.sockets.connected[socketid].emit();
Whatever version we are using if we just console.log() the "io" object that we use in our server side nodejs code, [e.g. io.on('connection', function(socket) {...});], we can see that "io" is just an json object and there are many child objects where the socket id and socket objects are stored.
I am using socket.io version 1.3.5, btw.
If we look in the io object, it contains,
sockets:
{ name: '/',
server: [Circular],
sockets: [ [Object], [Object] ],
connected:
{ B5AC9w0sYmOGWe4fAAAA: [Object],
'hWzf97fmU-TIwwzWAAAB': [Object] },
here we can see the socketids "B5AC9w0sYmOGWe4fAAAA" etc. So, we can do,
io.sockets.connected[socketid].emit();
Again, on further inspection we can see segments like,
eio:
{ clients:
{ B5AC9w0sYmOGWe4fAAAA: [Object],
'hWzf97fmU-TIwwzWAAAB': [Object] },
So, we can retrieve a socket from here by doing
io.eio.clients[socketid].emit();
Also, under engine we have,
engine:
{ clients:
{ B5AC9w0sYmOGWe4fAAAA: [Object],
'hWzf97fmU-TIwwzWAAAB': [Object] },
So, we can also write,
io.engine.clients[socketid].emit();
So, I guess we can achieve our goal in any of the 3 ways I listed above,
io.sockets.connected[socketid].emit();
OR
io.eio.clients[socketid].emit();
OR
io.engine.clients[socketid].emit();
You can do this
On server.
global.io=require("socket.io")(server);
io.on("connection",function(client){
console.log("client is ",client.id);
//This is handle by current connected client
client.emit('messages',{hello:'world'})
//This is handle by every client
io.sockets.emit("data",{data:"This is handle by every client"})
app1.saveSession(client.id)
client.on("disconnect",function(){
app1.deleteSession(client.id)
console.log("client disconnected",client.id);
})
})
//And this is handle by particular client
var socketId=req.query.id
if(io.sockets.connected[socketId]!=null) {
io.sockets.connected[socketId].emit('particular User', {data: "Event response by particular user "});
}
And on client, it is very easy to handle.
var socket=io.connect("http://localhost:8080/")
socket.on("messages",function(data){
console.log("message is ",data);
//alert(data)
})
socket.on("data",function(data){
console.log("data is ",data);
//alert(data)
})
socket.on("particular User",function(data){
console.log("data from server ",data);
//alert(data)
})
As of version 1.4.5, be sure you provide a properly prefixed socketId in io.to().
I was taking the socketId the Client logged to debug and it was without prefix so I ended up searching forever till I found out! So you might have to do it like this if the Id you have is not prefixed:
io.to('/#' + socketId).emit('myevent', {foo: 'bar'});
io.sockets.sockets[socket.id].emit(...) worked for me in v0.9
Also you can keep clients refferences. But this makes your memmory busy.
Create an empty object and set your clients into it.
const myClientList = {};
server.on("connection", (socket) => {
console.info(`Client connected [id=${socket.id}]`);
myClientList[socket.id] = socket;
});
socket.on("disconnect", (socket) => {
delete myClientList[socket.id];
});
then call your specific client by id from the object
myClientList[specificId].emit("blabla","somedata");
Socket.IO allows you to “namespace” your sockets, which essentially means assigning different endpoints or paths.
This might help:
http://socket.io/docs/rooms-and-namespaces/