How to send a message to a particular client with socket.io

javascript jquery ajax node.js socket.io

136,322

Solution 1

When a user connects, it should send a message to the server with a username which has to be unique, like an email.

A pair of username and socket should be stored in an object like this:

var users = {
    '[email protected]': [socket object],
    '[email protected]': [socket object],
    '[email protected]': [socket object]
}

On the client, emit an object to the server with the following data:

{
    to:[the other receiver's username as a string],
    from:[the person who sent the message as string],
    message:[the message to be sent as string]
}

On the server, listen for messages. When a message is received, emit the data to the receiver.

users[data.to].emit('receivedMessage', data)

On the client, listen for emits from the server called 'receivedMessage', and by reading the data you can handle who it came from and the message that was sent.

Solution 2

You can use socket.io rooms. From the client side emit an event ("join" in this case, can be anything) with any unique identifier (email, id).

Client Side:

var socket = io.connect('http://localhost');
socket.emit('join', {email: [email protected]});

Now, from the server side use that information to create an unique room for that user

Server Side:

var io = require('socket.io').listen(80);

io.sockets.on('connection', function (socket) {
  socket.on('join', function (data) {
    socket.join(data.email); // We are using room of socket io
  });
});

So, now every user has joined a room named after user's email. So if you want to send a specific user a message you just have to

Server Side:

io.sockets.in('[email protected]').emit('new_msg', {msg: 'hello'});

The last thing left to do on the client side is listen to the "new_msg" event.

Client Side:

socket.on("new_msg", function(data) {
    alert(data.msg);
}

I hope you get the idea.

Solution 3

SURE: Simply,

This is what you need :

io.to(socket.id).emit("event", data);

whenever a user joined to the server, socket details will be generated including ID. This is the ID really helps to send a message to particular people.

first we need to store all the socket.ids in array,

var people={};

people[name] =  socket.id;

here name is the receiver name. Example:

people["ccccc"]=2387423cjhgfwerwer23;

So, now we can get that socket.id with the receiver name whenever we are sending message:

for this we need to know the receivername. You need to emit receiver name to the server.

final thing is:

 socket.on('chat message', function(data){
io.to(people[data.receiver]).emit('chat message', data.msg);
});

Hope this works well for you.

Good Luck!!

Solution 4

You can refer to socket.io rooms. When you handshaked socket - you can join them to named room, for instance user.#{userid}.

After that, you can send private message to any client by convenient name, for instance:

io.sockets.in('user.125').emit('new_message', {text: "Hello world"})

In operation above we send "new_message" to user "125".

thanks.

Solution 5

As the az7ar answer is beautifully said but Let me make it simpler with socket.io rooms. request a server with a unique identifier to join a server. here we are using an email as a unique identifier.

Client Socket.io

socket.on('connect', function () {
  socket.emit('join', {email: [email protected]});
});

When the user joined a server, create a room for that user

Server Socket.io

io.on('connection', function (socket) {
   socket.on('join', function (data) {    
    socket.join(data.email);
  });
});

Now we are all set with joining. let emit something to from the server to room, so that user can listen.

Server Socket.io

io.to('[email protected]').emit('message', {msg: 'hello world.'});

Let finalize the topic with listening to message event to the client side

socket.on("message", function(data) {
  alert(data.msg);
});

The reference from Socket.io rooms

View more solutions

136,322

Nizar B.

Updated on July 14, 2022

Comments

Nizar B. almost 2 years

I'm starting with socket.io + node.js, I know how to send a message locally and to broadcast socket.broadcast.emit() function:- all the connected clients receive the same message.

Now, I would like to know how to send a private message to a particular client, I mean one socket for a private chat between 2 person (Client-To-Client stream). Thanks.
- Nizar B. almost 11 years
  
  Sorry psiphi75 but this link doesn't reply to my answer, isn't a duplicate question.
- softvar over 10 years
  
  @psiphi75, it's no way a duplicate
- Levi Roberts almost 9 years
  
  Can't stand people like @psiphi. Are you even a developer? How does an HTML5 specific question relate to a standalone library? And for what it's worth, WebSockets are NOT Socket.io. Socket.io is a library that can USE WebSockets, but I digress. This is also a more specific question relating to the library about sending data to only specific clients, not about the technology itself.
- bugwheels94 almost 7 years
  
  Possible duplicate of Send message to specific client with socket.io and node.js
- Nizar B. almost 7 years
  
  @bugwheels94 Not really, this post is from 2011 and since nodejs had loads of changes code-wise. this post is definitely a valid question/answer for this issue.
- bugwheels94 almost 7 years
  
  @Katcha There is an option called bounty in which there is again an option called "Current answers are outdated". Generally, this method should be used for this type of case
- Nizar B. almost 7 years
  
  @bugwheels94 Not sure what do you mean again but anyway.
Nizar B. almost 11 years

Hi mate, thanks you for your first answer, I will try it and let you know about that, because I don't want to build a chat but a private messenger like you can use on Facebook network.
Nizar B. almost 11 years

Can someone help me with this matter, I'm really stuck, I would like to add a username linked to my socket and allow my application to send a message to a specific user, no chat room, it's a Facebook like messenger. Thanks if you know!
Vladimir Kurijov almost 11 years

At first you have to understand that this username have to be unique across all users. And the second one - didn't you forget to subscribe for emitted message on the client side?
Vladimir Kurijov over 10 years

If you use this solution then you have to understand: 1. When user disconnects you have to clean up 'users' object 2. It doesnt support second connection - for instance from another browser. So if user connects from another browser - old connection will be overriden.
chovy over 10 years

how would you store the socket object in a datastore? I'm assuming this doesn't work if you have more than one node process.
chovy over 10 years

that client side looks like it would not be tied to a particular room.
az7ar over 10 years

client side does not have to know about rooms, your server subscribes your client to specific rooms. Client just has to listen on events and server side makes sure that client gets the events of client's subscribed rooms.
Vladimir Kurijov over 10 years

@chovy you have to use redis. Check this github.com/LearnBoost/Socket.IO/wiki/Configuring-Socket.IO
silvesterprabu about 10 years

please change this line io.socket.in('[email protected]').emit('new_msg', {msg: 'hello'}); like this io.sockets.in('[email protected]').emit('new_msg', {msg: 'hello'});
bluehallu about 10 years

The problem with this is that you loose the ability to use callbacks, as they are not allowed in broadcasts, which is what you really are doing here, a broadcast to his private room.
Daniel Que over 9 years

This answer is much better than the currently accepted answer. Here's why: 1) You don't have to manage and clean up the global array of clients. 2) It works even if a user has multiple tabs open on the same page. 3) It can be easily extended to work with a node cluster (multiple processes) with socket.io-redis.
Daniel Que over 9 years

I'd suggest to not use this solution. I ended up wasting a lot of time trying to overcome the limitations of this approach. See @az7ar's solution and this explanation for why it's better.
Aaron Lelevier about 9 years

@DanielQue +1. Way better to used native functionality. Thanks!
Daniel Que about 9 years

@AronYsidoro Glad my internet comment helped someone out!
miksiii about 9 years

@VladimirKurijov, Mr Katcha doesn't want to use Rooms and I agree it's not the solution to his problem.
turntwo about 9 years

I know this solution works very well and is the one I'm also actually using but since the premise here is that you create a unique room for each user (i.e. no room ever has more than one user connected to it), is there any caveat to creating a one-to-one correspondence between a live user and room (like how it is done here) , versus creating a single room and connecting all users to that room? Of course you have to manage the socket connections in the latter option as has been pointed out but in the first option, if say I have 1000 live users then this would mean I have to create 1000 rooms.
jack blank almost 9 years

how do you make {email: [email protected]} different for all connection wouldnt all clients that go to the app have user [email protected] how would i make it user [email protected] for the second client that connects so I could have different rooms. sorry if this is an annoying question.
Admin over 8 years

{ to:[the other receiver's username as a string], from:[the person who sent the message as string], message:[the message to be sent as string] } why as sting ??
Tejas Jadhav about 8 years

Loved this solution, though the accepted one is still a second good option.
Gopinath Shiva about 8 years

loved the solution, but I believe security is compromised here. What if I change the email in the script on the client side. Now I am able to read other private messages too. What are you saying?
Gopinath Shiva about 8 years

loved the solution, but I believe security is compromised here. What if I change the email in the script on the client side. Now I am able to read other private messages too. What are you saying?
az7ar about 8 years

it does not have to be email I mentioned any unique identifier
Adam about 8 years

The purpose of my answer was only to give people an understanding of how to transmit messages to others via a server in the most simple way I could think of without relying on the abstractions of rooms. I do not suggest that this is a complete solution for most applications.
Adam about 8 years

@GopinathShiva In a real application you would need to implement some type of user authentication when establishing the connection.
Dan about 8 years

This is awesome. I've been strugling with the docs for so long until i found this. Django docs ruined me for others.
mahdi pishguy almost 8 years

@Adam hi, could you yo helo me on this topic? stackoverflow.com/questions/38817680/…
mahdi pishguy almost 8 years

@az7ar hi, could you yo helo me on this topic? stackoverflow.com/questions/38817680/…
Aman Gupta over 7 years

"if say I have 1000 live users then this would mean I have to create 1000 rooms." from @turntwo . Is it good to create so many rooms for 1-to-1 chat. Also its oct'16 . is there any new/better approach for this.
Harish Mahajan over 7 years

Can you create a client side and server side code.? I am new in scoket programming. [email protected]
Trojan over 7 years

@HARISH, refer below link ,explains what really happening from client side..i hope this helps you more..socket.io/get-started/chat
Sharan Mohandas almost 7 years

But what if the user is chatting with 2 others at the same time. Won't the message from both user come in both windows?
lmenus over 6 years

@GopinathShiva That is a solid point raised which could be easily missed. Hopefully by the time the server sends back the response, it would've authenticated the client and if they have access to the given room. Otherwise it should not fetch the data from the room.
Mohhamad Hasham about 6 years

If there are more than two users, it won't work right
kiwicomb123 over 5 years

@GopinathShiva You could create a hashed roomId.
Abhi Burk over 4 years

My question is How will the second user join the room as the code above is joining the room with their own emails and it seems their is nothing common to join
Goran_Ilic_Ilke about 4 years

I think than people in explanation cant see main and esential difference between "rooms" && "namespace-s" and real private chat,i am trying to make that job with node ,socket.io && react whithout success months.
Vikas Kandari almost 4 years

each time users connects socket id changes so in case user opens your app in multiple tabs it will get response to one which you have stored and sent to other socket connections
Goran_Ilic_Ilke over 3 years

This aproachj looks nice but,seems to me than with socket.io we can only imitate private message logic,not to implement real one,must be other tool for js full chat apps.Cheers.
Rahul Gaur over 3 years

it seems your answer is a copy of @az7ar's answer from below, please give credits if you are using someone's answer with modification
Lalit Mohan over 3 years

Thank you @RahulGaur, Yes it is similar not a copy. But definitely my answer has changed. He used in to emit an event. But in my case, I have used to to emit an event. I hope you have seen this before
Rahul Gaur over 3 years

That's good to hear it's not a copy, but it seems inspired, so it is a good things to give credit
Lalit Mohan over 3 years

Noted Brother, Will do it definitely Thank you @RahulGaur.
Deepak saini over 3 years

this is not working with socket.io latest version(3.0.3)
kd12345 over 3 years

@Adam , hope you are good. I have a very similar question if you can please have a look at it. stackoverflow.com/questions/65277256/…
kd12345 over 3 years

@Deepaksaini hi, can you help me out. i have a very similar question regarding sockets. stackoverflow.com/questions/65277256/…
kd12345 over 3 years

@az7ar hi, i know it has been a while since your answer but i am stuck on a question very similar to this for weeks now. Can you please have a look, thank you in advance.stackoverflow.com/questions/65377025/…
kd12345 over 3 years

@MohhamadHasham hi, i know it has been a while since your answer but i am stuck on a question very similar to this for weeks now. Can you please have a look, thank you in advance.stackoverflow.com/questions/65377025/…
kd12345 over 3 years

@LalitMohan Hi, hope you are good. i know it has been a while since you answered this question, but your answer is the most that made sense to me. Can you please have a look at my question. stackoverflow.com/questions/65377025/…
DragonFire over 3 years

if it is a group just use the unique group id, but if it is between two users only one user can enter this chat first - so check for combination of both user id existence - if the room does not exist create one - use the combination and reverse combination of both user id to be checked
DragonFire over 3 years

I am surprised no one has looked at your solution... I posted the answer after that only I saw your answer...
unobatbayar over 2 years

I love the idea. Absolute genius.