Namespaces are a way of separating the business logic of your application while reusing the same TCP connection or minimizing the need for creating new TCP connections for to implement real-time communication between the server and the client.

Namespaces look pretty similar to ExpressJS' route paths:

/home 
/users 
/users/profile 

However, as mentioned in previous recipes, these are not related to URLs. By default, a single TCP connection is created at this URL http[s]://host:port/socket.io

Reusing the same event names is a good practice when using namespaces. For example, let's suppose that we have a Socket.IO server that we use to emit a setWelcomeMsg event when the client emits a getWelcomeMsg event:

io.of('/en').on('connection', (socket) => { 
    socket.on('getWelcomeMsg', () => { 
        socket.emit('setWelcomeMsg', 'Hello World!') 
    }) 
}) 
io.of('/es').on('connection', (socket) => { 
    socket.on('getWelcomeMsg', () => { 
        socket.emit('setWelcomeMsg', 'Hola Mundo!') 
    }) 
}) 

As you can see, we defined a listener for the event getWelcomeMsg in two different namespaces:

• If the client is connected to the English or /en namespace, when the setWelcomeMsg event is fired, the client will receive "Hello World!"
• On the other hand, if the client is connected to the Spanish or /es namespace, when the setWelcomeMsg event is fired, the client will receive "Hola Mundo!"