Node js chatting with multiple users in same room - node.js

Question

I am new to node.js. I am creating a chat app. I want to manage 4 users who are connected to the room. I have the primary key of the logged in user User A in the session, I can also save it in hidden file. When the page loads I only have one socket connected to server (i.e. socket of User A). When user A wants to chat with User B, I have a textarea for message, a div to show the chat message history and one send button.
How can I allow user A to chat with N number of users and keep track of who's chatting who?
I am thinking of following method to keep track of the chat messages,
Save both users primary key in hidden fields. When user A send message
to User B. Send User A and B's PK to server along with message and
save it in database.
or...
Is there any way to identify User B's Socket. So that Saving/Handling
User A and B's primary on client side can be avoided.

Answer 1

You can broadcast the message to all connected users.
io.sockets.emit("method","Message");
or you can send message to the specific user socket
io.sockets.socket(socketId).emit("method","Message");
Also you can add the users to the specific room on connection
io.sockets.on('connection', function (socket) {
socket.join("RoomName");
});
and send message to the room ( Message will deliver to all joined users )
io.to('RoomName').emit("method","Message");
You can get the socket id of user on connection and save it to array or database .
io.sockets.on('connection', function (socket) {
console.log( "User connected on " + socket.id);
});
Chat Application :
Node.js is single thread application.So You will have all connected user socket object stored in the io.sockets
Step 1: Save socket id of user in to database on Connection
Step 2: Remove Socket id of user from database on connection
Step 3: if socket id of user exist in database then this mean user is connected and you can send the message to user socket.
Node.js
// User Socket array storage
var user_by_socket = [];
var socket_to_users = [];
io.sockets.on('connection', function (socket) {
// Save Socket Object
user_by_socket[socket.id] = socket;
socket_to_user["Jhon"] = socket;
user_by_socket[socket.id] = socket;
socket_by_user["David"] = socket;
//Send Message
socket.on('send',function(data){
// Sent by username
socket_by_user["David"].emit("recieve","{ "From" : 'Jhon' , 'message' : "Hello" }");
//Sent by Socket Id
user_by_socket["Socket ID"].emit("recieve","{ "From" : 'Jhon' , 'message' : "Hello" }");
});
});