Push data to web socket by triggering externally

I want to push data to to all the connected socket when a rest api is called

I have a express based node js application.

On App launch, I create the socket server as mentioned in the docs.

And when the rest call is made, am pushing the data to socket client as

io.sockets.to('client_name').emit('message', 'Some message');

The problem is, this works fine, when I start the node/socket server and launch the client.

But when I restart the node/socket server , the client no longer receives the message. I will have to reload the client to start receiving the message.

What could be the issue