Add the "loopback" flag. #3640
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Add the "loopback" flag. #3640
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The "loopback" flag is used to emit messages on the local endpoint of a socket; e.g., allowing the server to send a message to the server's handler directly. This is especially useful in conjunction with rooms, as it allows the server to proactively trigger behavior for each socket in a room without having to maintain a separate list of said sockets or relying on the client endpoint to trigger the behavior.
This was referenced Feb 28, 2024
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The kind of change this PR does introduce
Current behaviour
It is not possible to send messages to the local (server) endpoint. In scenarios where rooms/broadcasts are used, this requires the server to maintain a separate room->socket mapping so that administrative actions can be performed (e.g., close all sockets in room 'foo').
New behaviour
With this change (and related PR socketio/socket.io-adapter#56), it is possible to emit/broadcast messages that are handled by the local (server) endpoint by inserting
.loopbackinto the emit syntax. On connect, the server can add handlers for messages that originate server-side, and later broadcast those messages in order to effect administrative actions (e.g., close all sockets in room 'foo') without maintaining independent mappings.Other information (e.g. related issues)
socketio/socket.io-adapter#56 must be committed before this change, as
socket.io-adapteris used in tests and must honour theloopbackflag.