Web socket helper project for Magic, giving you support for web sockets connections from and to Hyperlambda. To use package go to https://polterguy.github.io
This project provides web sockets hooks for for Magic.
The main idea of the project, is that it allows you to resolve Hyperlambda files, execute these,
passing in a URL and JSON arguments over a web socket connection - In addition to subscribing to messages
published by the server over a web socket connection. The project builds upon SignalR, but the internals are
completely abstracted away, and you could probably easily exchange SignalR with any other web socket
library with similar capabilities. The project contains one socket SignalR hub method with
the following signature.
execute(string file, string json);
To connect to the hub use the relative URL /sockets, optionally passing in a JWT token, and then
transmit messages to the hub using something such as for instance the following TypeScript.
let builder = new HubConnectionBuilder();
this.connection = builder.withUrl('http://localhost:5000/sockets', {
accessTokenFactory: () => 'return-your-JWT-token-here'
}).build();
this.connection.invoke(
'execute',
'/foo/some-hyperlambda-file',
JSON.stringify({
foo:'bar'
}));
The above will resolve to a Hyperlambda file expected to exist at /modules/foo/some-hyperlambda-file.socket.hl,
passing in the foo argument as lambda nodes.
[sockets.signal]
In addition to the above, you can explicitly publish SignalR events by signaling the [sockets.signal] slot,
which will automatically transform the specified children [args] nodes to JSON, and invoke the specified
method for all connections somehow subscribing to the specified method - Allowing you to filter according
to groups, users and roles if you wish. Below is an example.
The above will invoke the foo.bar method, passing in {"howdy":"world"} as a JSON string, but only users belonging
to the roles of either admin or root will be notified. Both the [roles] and the [args] arguments are optional.
To subscribe to the above invocation, you could use something such as the following in TypeScript.
The above will only signal the two specified client connections.
Notice - If you signal a group or a list of groups, you'll have to add your users to the group before
you do.
Arguments to [sockets.signal]
[roles] - Comma separated list of roles to send message to
[users] - Comma separated list of users to send message to
[clients] - Comma separated list of client connections to send message to
[groups] - Comma separated list of groups to send message to
[args] - Arguments to transmit to subscribers as JSON (string)
Only one of [users], [roles] or [groups] can be supplied, and all the above arguments are optional.
Groups and users
You can associate a user with one or more groups. This is done with the following slots.
[sockets.user.add-to-group] - Adds the specified user to the specified group
[sockets.user.remove-from-group] - Removes the specified user from the specified group
Below you can find an example of how to add a user to a group, for then to later de-associate
the user with the group.
// Associating a user with a group.
sockets.user.add-to-group:some-username-here
group:some-group-name-here
// Publishing message, now to group, such that 'some-username-here' gets it
sockets.signal:foo.bar
group:some-group-name-here
args
howdy:world
// De-associating the user with the group again.
sockets.user.remove-from-group:some-username-here
group:some-group-name-here
Notice - SignalR users might have multiple connections. This implies that once you add a user to
a group, all connections are associated with that group. The message will only be
published to connections explicitly having registered an interest in the foo.bar message for our
above example, irrelevant of whether the user belongs to the group or not.
Meta data
This project also allows you to retrieve meta data about currently connected users, through for instance
the [sockets.users] slot and the [sockets.users.count] slot, that will return the username of
all currently connected users, and the count matching your specified filter condition. An example
of using it can be found below.
Notice - If a client connected anonymously somehow over a socket, the client will (obviously)
not have a username, and the default userId will be returned instead. Also please notice, that each
user might have multiple connections, and this will return each connection for each username matching
the specified filter condition.
The filter conditions and paging arguments are optional, and will be null and 0-10 if not specified.
Connection context
From within your Hyperlambda files executed by invoking the execute method, you have access to
your SignalR connectionId as a context object named "sockets.connection". Below is an example of
how to retrieve the current SignalR connectionId. Notice, this only works from within a socket executed
Hyperlambda file, implying only if you're executing the file using the execute method, through your
SignalR socket connection.
get-context:sockets.connection
This might sometimes be useful, especially if you want to dynamically add only one connection to a group
for instance. To add the currently active connection explicitly to a group for instance, you can use the
following slots.
[sockets.connection.enter-group] - Associates the current connection only with the specified group
[sockets.connection.leave-group] - De-associates the current connection with the specified group
If the user has additional connections, none of the other connections will be modified in any ways. Also
realise that both of these slots can only be used from within a Hyperlambda file executed through a
SignalR socket connection somehow. Below is an example.
// Retrieving connectionId
get-context:sockets.connection
// Entering group
sockets.connection.enter-group:x:@get-context
group:foo-bar-group
// Do stuff here that requires the user to belong to group ...
// Leaving group
sockets.connection.leave-group:x:@get-context
group:foo-bar-group
Project website
The source code for this repository can be found at github.com/polterguy/magic.lambda.sockets, and you can provide feedback, provide bug reports, etc at the same place.
Quality gates
License
This project is the copyright(c) 2020-2021 of Thomas Hansen thomas@servergardens.com, and is licensed under the terms
of the LGPL version 3, as published by the Free Software Foundation. See the enclosed LICENSE file for details.
