Question

I have a simple express server (just showing the socket, the route is default):

io.on('connection', (socket) => {
  socket.emit('identify')
  
  socket.on('identity', (data) => {
    activeUsers.push(data['name'])
    socket.name = data['name']
    console.log('Connection from ' + socket.name)
  });

  io.on('disconnect', (data) => {
    activeUsers.splice(indexOf(socket.name))
    console.log(socket.name + ' disconnected.')
  })
  
  io.on('message', (data) => {
    console.log(data['message'])
  });
});

I then wrote a python client, and connection worked fine:

@io.event
def connect():
  print('connected')

@io.on("identify")
def identity():
  io.emit("identity", {"name": "isaiah08"})

However, when i changed identify to be:

@io.on("identify")
def identity():
  io.emit("identity", {"name": "isaiah08"})
  io.emit("message", {"message": "I WILL EAT YOU"})

It did not log the message. Why is this?

Note

Yes, I created a socket in the / route:

<script>
  var socket = io();
</script>

And I am connection to the right website.

You aren't registering the event handler for message correctly on your server, so the message is arriving, but your message handler to receive it isn't configured properly.

Change this:

  io.on('disconnect', (data) => {
    activeUsers.splice(indexOf(socket.name))
    console.log(socket.name + ' disconnected.')
  })
  
  io.on('message', (data) => {
    console.log(data['message'])
  });

to this:

  socket.on('disconnect', (data) => {
    activeUsers.splice(indexOf(socket.name))
    console.log(socket.name + ' disconnected.')
  })
  
  socket.on('message', (data) => {
    console.log(data['message'])
  });

These messages come to the socket, not to the io object. You wrote it correctly with the "identify" message, but not with these other two messages.