How to send file to a particular user in nodejs - node.js

Question

I am creating a rest api on nodejs. I have email id and user id in database. I want to share a file (present on same server) from one user to a particular user. Can anyone tell me how this can be done in a best way ?
Here is the code i have tried yet.
const server = require('./../server/server.js')
const socketIO = require('socket.io');
const io = socketIO(server);
const mongoose = require('mongoose');
const User = require('../models/user.js');
let sockets = [];
io.on('connection', socket=>{
console.log("User connected");
socket.on('online', (data)=>{
socket.name = data._id;
sockets[data._id] = socket.id;
console.log("user is online")
})
socket.on('send_file', (data)=>{
User.find({emailId: data},{emailId:0, password:0})
.exec()
.then(userid => {
if(userid.length<1){
console.log("No such user");
}
else{
console.log(userid[0].id);
socket.to(sockets[userid[0].id]).emit('hello', "HELLO");
}
})
.catch(err =>{
console.log(err);
});
});
socket.on('disconnect', ()=>{
console.log("User disconnected");
})
})
module.exports = io;
server.listen('8080', (err)=>{
if(err) throw err;
console.log("running on port 8080");
});

Answer 1

Assuming that you have already configured the socketio and express sever properly with he mechanism to save the file path and file name in you database.
Try something like this (with socketio)
let sockets = [];
io.on("connection", function(socket) {
socket.on("online", data => {
socket.name = data.username;
sockets[data.username] = socket.id;
});
socket.on("send_file", function(data) {
// your logic to retrieve the file path from you database in to the variable **filedata**
// let filedata = ................
socket.to(sockets[data.user]).emit("file",filedata);
});
socket.on("disconnect", reason => {
sockets.splice(sockets.findIndex(id => id === socket.id), 1);
});
});
in send_file event you will have receive the username from the sender inside the data object. The following code will be one which will help you to send file to selected user.
socket.to(sockets[data.user]).emit("file",filedata);
Replying to your 1st comment.
history.push() will not refresh the client since its a single page application.
But when you refresh(from user A side) a new socket session will be created then the other user(user B) will still be referring the old socket session(which is already being disconnected by the refresh). So to handle this use the following lines
socket.on("online", data => {
socket.name = data.username;
sockets[data.username] = socket.id;
});
where you will be keeping a pool(an array) of sockets with the usernames so when ever a user refresh their client the newly created socket will be referring to the same user. Since you will be updating the the socket.id to the same person.
For example assume that you the user who refresh the client and im the other user. so when you refresh a new socket session will be created an it will be sent to the back end along with the user name. When the data comes to the server it will get your session object from the array(sockets[data.username]) and update it with the new socketio sent from your front-end sockets[data.username] = socket.id;.
for this to happen you will have to send the user name along with the socket message. like this
socket.emit("online", {
username: "username"
});
Replying to your 2nd comment
To send data in real time the users should be online. if not you can just create an array of notifications with the following information (sender and receiver). So when the receiver logs in or clicks on the notification panel the list of shared files notification can be shown. This is just a suggestion you can come up with you own idea. Hope this helps.

Answer 2

In case of Non-real time data:
Server Side-:
use res.sendFile() is a way to solve this problem. In addition to file send the receiver and sender id in headers
Client Side-:
Increase the notification count if the receiver id matches the logged in user.
res.sendFile(path.join("path to file"),
{headers:{
receiverid:result[0]._id,
senderid:result[1]._id
}
});
In case of real time data:
follow the answer posted by TRomesh