Standards:GMCP Client Variables
GMCP Client Variables Sharing Standard
Overview and Rationale
The GMCP Client Variables Sharing extension provides a standardized way to exchange client-specific variables between MUD clients and game servers using GMCP messages. This facilitates enhanced user experiences by allowing servers to adjust gameplay and UI elements based on client-provided data.
Specification for Client.Variables
Commands - Server
Client.Variables.Default
‘’‘Purpose’’’: Sent by the server to acknowledge support for the Client.Variables namespace.
Client.Variables.Default {}
Client.Variables.List
‘’‘Purpose’’’: The client sends a list of available client variables and their attributes.
Client.Variables.List {
“256_COLORS”: {“available”: true, “updatable”: false},
“ANSI”: {“available”: true, “updatable”: false},
“BOLD_IS_BRIGHT”: {“available”: true, “updatable”: true},
“CHARSET”: {“available”: true, “updatable”: true},
“CLIENT_NAME”: {“available”: true, “updatable”: false},
“CLIENT_VERSION”: {“available”: true, “updatable”: false},
“FONT”: {“available”: false, “updatable”: false},
“FONT_SIZE”: {“available”: false, “updatable”: false},
“LANGUAGE”: {“available”: false, “updatable”: false},
“MTTS”: {“available”: true, “updatable”: false},
“OSC_COLOR_PALETTE”: {“available”: true, “updatable”: false},
“SCREEN_READER”: {“available”: false, “updatable”: false},
“SYSTEMTYPE”: {“available”: false, “updatable”: false},
“TERMINAL_TYPE”: {“available”: true, “updatable”: false},
“TLS”: {“available”: true, “updatable”: false},
“TRUECOLOR”: {“available”: true, “updatable”: false},
“USER”: {“available”: false, “updatable”: false},
“UTF-8”: {“available”: true, “updatable”: false},
“VT100”: {“available”: true, “updatable”: false},
“WORD_WRAP”: {“available”: true, “updatable”: false}
}
Client.Variables.Request
‘’‘Purpose’’’: The server requests specific client variables.
Client.Variables.Request [“BOLD_IS_BRIGHT”, “CHARSET”, “FONT”, “FONT_SIZE”, “LANGUAGE”, “SCREEN_READER”, “SYSTEMTYPE”, “USER”]
Client.Variables.Update
‘’‘Purpose’’’: The client sends updates for requested variables.
Client.Variables.Update {
“BOLD_IS_BRIGHT”: {
“available”: true,
“updatable”: true,
“requested”: false,
“source”: “request”,
“timestamp”: 1721495879,
“value”: 2
},
“CHARSET”: {
“available”: true,
“updatable”: true,
“requested”: false,
“source”: “request”,
“timestamp”: 1721495879,
“value”: “UTF-8”
},
“FONT”: {
“available”: false,
“updatable”: false,
“requested”: true,
“source”: “request”,
“timestamp”: 1721495879
},
“FONT_SIZE”: {
“available”: false,
“updatable”: false,
“requested”: true,
“source”: “request”,
“timestamp”: 1721495879
},
“LANGUAGE”: {
“available”: false,
“updatable”: false,
“requested”: true,
“source”: “request”,
“timestamp”: 1721495879
},
“SCREEN_READER”: {
“available”: false,
“updatable”: false,
“requested”: true,
“source”: “request”,
“timestamp”: 1721495879
},
“SYSTEMTYPE”: {
“available”: false,
“updatable”: false,
“requested”: true,
“source”: “request”,
“timestamp”: 1721495879
},
“USER”: {
“available”: false,
“updatable”: false,
“requested”: true,
“source”: “request”,
“timestamp”: 1721495879
}
}
Client.Variables.Set
‘’‘Purpose’’’: The server sets specific client variables.
Client.Variables.Set {
“BOLD_IS_BRIGHT” : “1”
}
Implementation Considerations
- ‘’‘Client Support Advertisement’’’: Clients should advertise their support for the Client.Variables namespace using Core.Supports.Set.
- ‘’‘Server Acknowledgement’’’: Servers acknowledge support with Client.Variables.Default.
- ‘’‘Consent Management’’’: Clients must handle user consent for sharing sensitive variables. Prompts should inform users of requested data and allow them to opt-in or block requests.
- ‘’‘Variable Updates’’’: Clients should manage variable updates efficiently, ensuring data integrity and user consent.
Example Flow
1. ‘’‘Client’’’: Advertises support.
Core.Supports.Set ["Client.Variables 1", ...]
2. ‘’‘Server’’’: Acknowledges support.
Client.Variables.Default {}
3. ‘’‘Client’’’: Sends available variables list.
Client.Variables.List {
"256_COLORS": {"available": true, "updatable": false},
"ANSI": {"available": true, "updatable": false},
"BOLD_IS_BRIGHT": {"available": true, "updatable": true},
"CHARSET": {"available": true, "updatable": true},
"CLIENT_NAME": {"available": true, "updatable": false},
"CLIENT_VERSION": {"available": true, "updatable": false},
"FONT": {"available": false, "updatable": false},
"FONT_SIZE": {"available": false, "updatable": false},
"LANGUAGE": {"available": false, "updatable": false},
"MTTS": {"available": true, "updatable": false},
"OSC_COLOR_PALETTE": {"available": true, "updatable": false},
"SCREEN_READER": {"available": false, "updatable": false},
"SYSTEMTYPE": {"available": false, "updatable": false},
"TERMINAL_TYPE": {"available": true, "updatable": false},
"TLS": {"available": true, "updatable": false},
"TRUECOLOR": {"available": true, "updatable": false},
"USER": {"available": false, "updatable": false},
"UTF-8": {"available": true, "updatable": false},
"VT100": {"available": true, "updatable": false},
"WORD_WRAP": {"available": true, "updatable": false}
}
4. ‘’‘Server’’’: Requests specific variables.
Client.Variables.Request ["BOLD_IS_BRIGHT", "CHARSET", "FONT", "FONT_SIZE", "LANGUAGE", "SCREEN_READER", "SYSTEMTYPE", "USER"]
5. ‘’‘Client’’’: Updates requested variables.
Client.Variables.Update {
"BOLD_IS_BRIGHT": {
"available": true,
"updatable": true,
"requested": false,
"source": "request",
"timestamp": 1721495879,
"value": 2
},
"CHARSET": {
"available": true,
"updatable": true,
"requested": false,
"source": "request",
"timestamp": 1721495879,
"value": "UTF-8"
},
"FONT": {
"available": false,
"updatable": false,
"requested": true,
"source": "request",
"timestamp": 1721495879
},
"FONT_SIZE": {
"available": false,
"updatable": false,
"requested": true,
"source": "request",
"timestamp": 1721495879
},
"LANGUAGE": {
"available": false,
"updatable": false,
"requested": true,
"source": "request",
"timestamp": 1721495879
},
"SCREEN_READER": {
"available": false,
"updatable": false,
"requested": true,
"source": "request",
"timestamp": 1721495879
},
"SYSTEMTYPE": {
"available": false,
"updatable": false,
"requested": true,
"source": "request",
"timestamp": 1721495879
},
"USER": {
"available": false,
"updatable": false,
"requested": true,
"source": "request",
"timestamp": 1721495879
}
}
Conclusion
The GMCP Variables Sharing extension standardizes the exchange of client-specific variables, ensuring seamless integration and enhanced user experiences. By adopting this standard, MUD developers can streamline variable management, improve client-server communication, and provide more personalized gaming experiences.
Versions
- Version 1.0: Initial specification.
Authors
- Mike Conley (Tamarindo, Administrator at StickMUD and Mudlet contributor) mike.conley[at]stickmud.com
Notes
- This specification is subject to updates and community input. Contributions and feedback are welcome to ensure it meets the needs of the MUD community.
- Implementation should follow GMCP protocol specifications, and all messages must be well-formatted JSON objects.