Bar data

Opening times, live stock, prices and sales data for the Bar and Cybar.

2026 Bars

There is a simple read-only interface to the till system running the main bar, Null Sector bar and the “secret” bar. It’s available via HTTP GET from bar.emf.camp and returns JSON, except when you request an object that does not exist when it will return HTTP 404.

Some types of object can be subscribed to over a websocket connection. These objects have a property “key” that you can use to identify them. You will receive a fresh copy of the object over the websocket connection immediately after subscription, and then again whenever the object is updated. The websocket is at wss://bar.emf.camp/websocket/

All the objects available over the websocket connection are also published over MQTT with the prefix bar/ followed by the key, for example bar/stockline/100. More details are below.

The web service that implements this API is here.

Data types

All these data types are represented as JSON objects. Integers are represented as JSON numbers, Decimals are represented as JSON strings, times are local times in ISO 8601 format.

Error

Only received over a websocket connection. Sent when the websocket server can’t parse your request.

Properties:

type: the string “error”
message: a description of the problem

Example:

{
  "type": "error",
  "message": "Invalid request"
}

Not present

Only received over a websocket connection. Sent when the key you subscribed to does not exist, or ceases to exist. The subscription remains valid and if the key is created in the future you will receive it.

Properties:

type: the string “not present”
key: the key that is not present

Example:

{
  "type": "not present",
  "key": "stocktype/12345"
}

Session

A time period that the bar is planned to be open.

Properties:

type: the string “session”
opening_time: opening time in localtime
closing_time: closing time in localtime

Example showing opening from 11am to 1am on Friday:

{
  "type": "session",
  "opening_time": "2026-07-17T11:00:00+01:00",
  "closing_time": "2027-07-18T01:00:00+01:00"
}

Department

Everything sold through the till has a “department”, which is a general classification by type (real ale, keg, wine, etc.)

Properties:

type: the string “department”
id: an integer uniquely identifying the department
description: a string describing the department
notes: an optional string giving more information

Example:

{
  "type": "department",
  "id": 90,
  "description": "Wine (bottles)",
  "notes": "Available in 125ml, 175ml and 250ml"
}

Stock type

Properties:

type: the string “stocktype”
key: the object’s websocket key
id: an integer uniquely identifying the stock type
department: the Department object associated with the stock type
manufacturer: a string naming the manufacturer
name: a string describing this type of stock; unique per manufacturer
abv: an optional Decimal giving the alcohol by volume
fullname: manufacturer, name and abv combined into a single string
price: the sale price as a Decimal, including VAT where appropriate, for a sale_unit_name of this type of stock
logo: the path to a PNG logo, or null if not present
tasting_notes: tasting notes as HTML, or null if not present
base_units_bought: the amount of stock bought in base units as a Decimal
base_units_remaining: the amount of stock remaining in base units as a Decimal
base_unit_name: a string giving the unit in which we count how much of this stock we have bought and sold, eg. “pint” or “ml”
sale_unit_name: a string giving the unit in which we sell this type of stock, eg. “bottle” or “pint”
sale_unit_name_plural: plural form of sale_unit_name
base_units_per_sale_unit: the number of base units per sale unit as a Decimal
stock_unit_name: a string giving the unit in which we count this type of stock, eg. “pint” or “1l carton”
stock_unit_name_plural: plural form of stock_unit_name
base_units_per_stock_unit: the number of base units per stock unit as a Decimal
stocklines: a list of stockline-brief objects (see below) describing places stock of this type is being sold

Examples:

{
  "type": "stocktype",
  "key": "stocktype/1",
  "id": 1,
  "department": {
    "type": "department",
    "id": 20,
    "description": "Craft Keg >0.5%",
    "notes": ""
  },
  "manufacturer": "Milton",
  "name": "Dynamo",
  "abv": "3.9",
  "fullname": "Milton Dynamo (3.9% ABV)",
  "price": "4.80",
  "logo": "/media/emf/product-logos/f6ecbcf8bac0d2ac95791a9aad246666fe2c3a48924966145f914d8b645cc4f7.png",
  "tasting_notes": null,
  "base_units_bought": "1056.0",
  "base_units_remaining": "1056.0",
  "base_unit_name": "pint",
  "sale_unit_name": "pint",
  "sale_unit_name_plural": "pints",
  "base_units_per_sale_unit": "1.0",
  "stock_unit_name": "pint",
  "stock_unit_name_plural": "pints",
  "base_units_per_stock_unit": "1.0",
  "stocklines": []
}

{
  "type": "stocktype",
  "key": "stocktype/28",
  "id": 28,
  "department": {
    "type": "department",
    "id": 70,
    "description": "Soft Drink Cartons",
    "notes": null
  },
  "manufacturer": "Sunpride",
  "name": "Apple Juice",
  "abv": null,
  "fullname": "Sunpride Apple Juice",
  "price": "2.00",
  "logo": "/media/emf/product-logos/9a1b8e1a442a450611d952161900f0582d34d21522fe2ee293ac79a4f0e4bebf.png",
  "tasting_notes": null,
  "base_units_bought": "0.0",
  "base_units_remaining": "0.0",
  "base_unit_name": "ml",
  "sale_unit_name": "pint",
  "sale_unit_name_plural": "pints",
  "base_units_per_sale_unit": "568.0",
  "stock_unit_name": "litre",
  "stock_unit_name_plural": "litres",
  "base_units_per_stock_unit": "1000.0",
  "stocklines": [
    {
      "type": "stockline-brief",
      "key": "stockline/123",
      "id": 123,
      "name": "Apple Juice",
      "location": "Fridge",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "continuous"
    }
  ]
}

Stock item

Some types of stock are divided into “items”, for example we may have three casks of a particular type of beer. When they are put on sale on the bar, the amount remaining is counted for each item as well as for the type of stock as a whole.

Properties:

type: the string “stockitem”
key: the object’s websocket key
id: an integer uniquely identifying the stock item
stocktype: the StockType object for the stock item
description: a description of the item, for example “Firkin” or “50l keg”
remaining: the number of base units remaining of this stock item
size: the number of base units originally in this stock item
remaining_pct: a Decimal representing the percentage of this item that is remaining

Example:

{
  "type": "stockitem",
  "key": "stockitem/3",
  "id": 3,
  "stocktype": {
    "type": "stocktype",
    "key": "stocktype/2",
    "id": 2,
    "department": {
      "type": "department",
      "id": 10,
      "description": "Real Ale",
      "notes": null
    },
    "manufacturer": "Milton",
    "name": "Justinian",
    "abv": "3.9",
    "fullname": "Milton Justinian (3.9% ABV)",
    "price": "4.70",
    "logo": "/media/emf/product-logos/cea539af1f7ebb03344d9458355bf6426f83c96dbf243a69e340a70b43935c54.png",
    "tasting_notes": "<p>Crisp pale bronze-coloured bitter. Attractive bitter orange flavours persist into a satisfying lasting finish.</p>",
    "base_units_bought": "576.0",
    "base_units_remaining": "576.0",
    "base_unit_name": "pint",
    "sale_unit_name": "pint",
    "sale_unit_name_plural": "pints",
    "base_units_per_sale_unit": "1.0",
    "stock_unit_name": "pint",
    "stock_unit_name_plural": "pints",
    "base_units_per_stock_unit": "1.0",
    "stocklines": []
  },
  "description": "Kilderkin",
  "remaining": "144.0",
  "size": "144.0",
  "remaining_pct": "100.00"
}

Location

Stock lines (see below) may be associated with a physical location. These locations are described by a Location object.

Properties:

slug: the internal name for the location; in 2026 this will be one of “robotarms”, “cybar”, “spacebar” or “unknown”
name: a human readable name for the location
maplink: if not null, a URL pointing at the location on map.emfcamp.org

(sort can be ignored.)

Example:

{
  "sort": 1,
  "slug": "robotarms",
  "name": "Robot Arms",
  "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
}

Stock line

Everything sold on the till is sold through a “stock line”. In some cases, this is a physical thing: a hand pump on the bar, a keg tap, or a place on the bar where we keep boxes of cider. In other cases, it’s just an abstract thing, for example “the Orange Juice is currently Princes Orange Juice cartons”.

There are two variants of the StockLine object. The “full” variant has type “stockline” and has all the properties listed below. The “brief” variant has type “stockline-brief” and does not have the stockitem or stocktype properties.

Properties:

type: the string “stockline” or “stockline-brief”
key: the object’s websocket key
id: an integer uniquely identifying the stock line
name: a string describing this stock line
location: a string describing the physical location of this stock line (for internal use by the bars)
location_display: a Location object describing the physical location of this stock line
note: a string describing the state of this stock line or the product on sale on it; may be blank
linetype: a string describing the type of line; this will be regular for lines where particular stock items are put on sale, or continuous for lines where a whole stock type is on sale
stockitem: the StockItem object on sale on this stock line, if the line is of type regular and there is something on sale on it; otherwise null
stocktype: the StockType object on sale on this stock line, if the line is of type continuous; otherwise null

Examples:

{
  "type": "stockline",
  "key": "stockline/104",
  "id": 104,
  "name": "Tap 1",
  "location": "Bar",
  "location_display": {
    "sort": 1,
    "slug": "robotarms",
    "name": "Robot Arms",
    "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
  },
  "note": "Example",
  "linetype": "regular",
  "stockitem": {
    "type": "stockitem",
    "key": "stockitem/3",
    "id": 3,
    "stocktype": {
      "type": "stocktype",
      "key": "stocktype/1",
      "id": 1,
      "department": {
        "type": "department",
        "id": 20,
        "description": "Craft Keg >0.5%",
        "notes": null
      },
      "manufacturer": "Milton",
      "name": "Dynamo",
      "abv": "3.9",
      "fullname": "Milton Dynamo (3.9% ABV)",
      "price": "5.00",
      "logo": "/media/emf/product-logos/f6ecbcf8bac0d2ac95791a9aad246666fe2c3a48924966145f914d8b645cc4f7.png",
      "tasting_notes": null,
      "base_units_bought": "1056.0",
      "base_units_remaining": "1056.0",
      "base_unit_name": "pint",
      "sale_unit_name": "pint",
      "sale_unit_name_plural": "pints",
      "base_units_per_sale_unit": "1.0",
      "stock_unit_name": "pint",
      "stock_unit_name_plural": "pints",
      "base_units_per_stock_unit": "1.0"
    },
    "remaining": "88.0",
    "size": "88.0"
    "remaining_pct": "100.00"
  },
  "stocktype": null
}

{
  "type": "stockline",
  "key": "stockline/130",
  "id": 130,
  "name": "Club Mate Regular",
  "location": "Fridge",
  "location_display": {
    "sort": 1,
    "slug": "robotarms",
    "name": "Robot Arms",
    "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
  },
  "note": "",
  "linetype": "continuous",
  "stockitem": null,
  "stocktype": {
    "type": "stocktype",
    "key": "stocktype/8",
    "id": 8,
    "department": {
      "type": "department",
      "id": 75,
      "description": "Club Mate",
      "notes": null
    },
    "manufacturer": "Club Mate",
    "name": "Regular",
    "abv": null,
    "fullname": "Club Mate Regular",
    "price": "2.40",
    "logo": "/media/emf/product-logos/f38444690c6b28a8dbd6a238c1741d36dd6990aa09243dda4c30513292580a8e.png",
    "tasting_notes": null,
    "base_units_bought": "640.0",
    "base_units_remaining": "640.0",
    "base_unit_name": "500ml bottle",
    "sale_unit_name": "500ml bottle",
    "sale_unit_name_plural": "500ml bottles",
    "base_units_per_sale_unit": "1.0",
    "stock_unit_name": "500ml bottle",
    "stock_unit_name_plural": "500ml bottles",
    "base_units_per_stock_unit": "1.0",
    "stocklines": [
      {
        "type": "stockline-brief",
        "key": "stockline/130",
        "id": 130,
        "name": "Club Mate Regular",
        "location": "Fridge",
        "location_display": {
          "sort": 1,
          "slug": "robotarms",
          "name": "Robot Arms",
          "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
        },
        "note": "",
        "linetype": "continuous"
      }
    ]
  }
}

Endpoints

All endpoints return JSON objects; where an endpoint needs to return a list, it returns an object with the list as the value of a key.

Sessions

/api/sessions.json returns a list of current and future bar Sessions.

Example (N.B. the times in this example are not final and may change during the event based on available volunteers, etc.):

{
  "sessions": [
    {
      "type": "session",
      "opening_time": "2026-07-15T20:00:00+01:00",
      "closing_time": "2026-07-15T23:00:00+01:00"
    },
    {
      "type": "session",
      "opening_time": "2026-07-16T15:00:00+01:00",
      "closing_time": "2026-07-17T00:30:00+01:00"
    },
    {
      "type": "session",
      "opening_time": "2026-07-17T11:00:00+01:00",
      "closing_time": "2027-07-18T01:00:00+01:00"
    },
    {
      "type": "session",
      "opening_time": "2026-07-18T11:00:00+01:00",
      "closing_time": "2026-07-19T01:00:00+01:00"
    },
    {
      "type": "session",
      "opening_time": "2026-07-19T11:00:00+01:00",
      "closing_time": "2026-07-20T01:00:00+01:00"
    }
  ]
}

Event progress

/api/progress.json returns general information about bar progress.

Although this drives a couple of graphs on the bar web site it is not intended to be scientifically accurate!

Properties (all Decimal percentages):

licensed_time_pct: how far through the sessions are we at the moment?
expected_consumption_pct: how far through the sessions are we at the moment, with a weighting applied per session based on experience at previous events?
actual_consumption_pct: how much of the booze have we used? “Booze” is any stock type with a non-null abv, including those with an abv of “0.0”.

Example:

{
  "licensed_time_pct": "0",
  "expected_consumption_pct": "0",
  "actual_consumption_pct": "0"
}

Departments

/api/departments.json returns the complete list of Departments.

Example:

{
  "departments": [
    {
      "type": "department",
      "id": 10,
      "description": "Real Ale",
      "notes": null
    },
    /* many departments omitted */
    {
      "type": "department",
      "id": 100,
      "description": "Cup re-use",
      "notes": null
    }
  ]
}

Beers and ciders on tap

/api/on-tap.json returns lists of Stock items on sale on the bar at the moment. The list is divided in to real ales (on handpumps), keg beers and ciders (on taps) and real ciders (sold from boxes on the bar).

Properties:

ales: list of real ale Stock items
kegs: list of keg beer/cider Stock items
ciders: list of real cider Stock items

/api/cybar-on-tap.json returns lists of Stock items on sale on the bar in Null Sector. The list is divided in to keg beers and ciders (on taps) and real ciders (sold from boxes on the bar).

Properties:

kegs: list of keg beer/cider Stock items
ciders: list of real cider Stock items

Example from /api/on-tap.json:

{
  "ales": [],
  "kegs": [
    {
      "type": "stockitem",
      "key": "stockitem/3",
      "id": 3,
      "stocktype": {
        "type": "stocktype",
        "key": "stocktype/1",
        "id": 1,
        "department": {
          "type": "department",
          "id": 20,
          "description": "Craft Keg",
          "notes": null
        },
        "manufacturer": "Milton",
        "name": "Dynamo",
        "abv": "3.9",
        "fullname": "Milton Dynamo (3.9% ABV)",
        "price": "5.00",
        "logo": "/media/emf/product-logos/f6ecbcf8bac0d2ac95791a9aad246666fe2c3a48924966145f914d8b645cc4f7.png",
        "tasting_notes": null,
        "base_units_bought": "1056.0",
        "base_units_remaining": "1056.0",
        "base_unit_name": "pint",
        "sale_unit_name": "pint",
        "sale_unit_name_plural": "pints",
        "base_units_per_sale_unit": "1.0",
        "stock_unit_name": "pint",
        "stock_unit_name_plural": "pints",
        "base_units_per_stock_unit": "1.0"
      },
      "remaining": "88.0",
      "size": "88.0",
      "remaining_pct": "100.00"
    }
  ],
  "ciders": []
}

All stock types

/api/stocktypes.json lists all the types of stock remaining at the bar and cybar.

⚠️This is a fairly expensive API call, please do not poll it! If you want to receive updates, save the object keys and subscribe to the objects over the websocket or MQTT.

Example:

{
  "stocktypes": [
    {
      "type": "stocktype",
      "key": "stocktype/16",
      "id": 16,
      "department": {
        "type": "department",
        "id": 10,
        "description": "Real Ale",
        "notes": null
      },
      "manufacturer": "Ledbury",
      "name": "Admiral Parker Pale Ale",
      "abv": "4.0",
      "fullname": "Ledbury Admiral Parker Pale Ale (4.0% ABV)",
      "price": "5.00",
      "logo": "/media/emf/product-logos/40bf1d101e329f015fb74b597a372e4fe3bce75eb11504b95b1984c3708b518c.png",
      "tasting_notes": "<p>This 4% pale only uses hops grown by Simon Parker at Instone Court in Bishops Frome. We have Simon’s Admiral, Opus, Ernest and Emperor hops. It is amazing that you can get the complex aromas of Orange, Lemon, Mint, Peach, Tea, Lime, Apricots and Pepper from not just locally grown hops but from hops grown on a single farm in Herefordshire.</p>",
      "base_units_bought": "144.0",
      "base_units_remaining": "144.0",
      "base_unit_name": "pint",
      "sale_unit_name": "pint",
      "sale_unit_name_plural": "pints",
      "base_units_per_sale_unit": "1.0",
      "stock_unit_name": "pint",
      "stock_unit_name_plural": "pints",
      "base_units_per_stock_unit": "1.0"
    },
    /* many, many stocktypes omitted! */
    {
      "type": "stocktype",
      "key": "stocktype/32",
      "id": 32,
      "department": {
        "type": "department",
        "id": 90,
        "description": "Wine Bottles",
        "notes": "Available in 125ml, 175ml and 250ml"
      },
      "manufacturer": "Inkosi",
      "name": "Sauvignon Blanc",
      "abv": "13.5",
      "fullname": "Inkosi Sauvignon Blanc (13.5% ABV)",
      "price": "20.00",
      "logo": null,
      "tasting_notes": null,
      "base_units_bought": "27000.0",
      "base_units_remaining": "27000.0",
      "base_unit_name": "ml",
      "sale_unit_name": "bottle",
      "sale_unit_name_plural": "bottles",
      "base_units_per_sale_unit": "750.0",
      "stock_unit_name": "bottle",
      "stock_unit_name_plural": "bottles",
      "base_units_per_stock_unit": "750.0"
    }
  ]
}

All stock types in a department

You can retrieve all stock types in a department using /api/department/<int:dept_id>.json. If you know the department ID, this is more efficient than retrieving everything from /api/stocktypes.json and filtering locally.

⚠️This is a fairly expensive API call, please do not poll it! If you want to receive updates, save the object keys and subscribe to the objects over the websocket or MQTT.

For example, to retrieve the Club Mate stock levels you can fetch from /api/department/75.json:

{
  "stocktypes": [
    {
      "type": "stocktype",
      "key": "stocktype/9",
      "id": 9,
      "department": {
        "type": "department",
        "id": 75,
        "description": "Club Mate",
        "notes": null
      },
      "manufacturer": "Club Mate",
      "name": "Granat 500ml",
      "abv": null,
      "fullname": "Club Mate Granat 500ml",
      "price": "2.80",
      "logo": "/media/emf/product-logos/e4852de71fb174907169b8b011a751e5bcb34efa60ce5683a167d8d9e1b75f36.png",
      "tasting_notes": null,
      "base_units_bought": "700.0",
      "base_units_remaining": "700.0",
      "base_unit_name": "bottle",
      "sale_unit_name": "bottle",
      "sale_unit_name_plural": "bottles",
      "base_units_per_sale_unit": "1.0",
      "stock_unit_name": "bottle",
      "stock_unit_name_plural": "bottles",
      "base_units_per_stock_unit": "1.0"
    },
    {
      "type": "stocktype",
      "key": "stocktype/8",
      "id": 8,
      "department": {
        "type": "department",
        "id": 75,
        "description": "Club Mate",
        "notes": null
      },
      "manufacturer": "Club Mate",
      "name": "Regular 500ml",
      "abv": null,
      "fullname": "Club Mate Regular 500ml",
      "price": "2.80",
      "logo": "/media/emf/product-logos/f38444690c6b28a8dbd6a238c1741d36dd6990aa09243dda4c30513292580a8e.png",
      "tasting_notes": null,
      "base_units_bought": "1700.0",
      "base_units_remaining": "1700.0",
      "base_unit_name": "bottle",
      "sale_unit_name": "bottle",
      "sale_unit_name_plural": "bottles",
      "base_units_per_sale_unit": "1.0",
      "stock_unit_name": "bottle",
      "stock_unit_name_plural": "bottles",
      "base_units_per_stock_unit": "1.0"
    }
  ]
}

Retrieve a specific stock type

If you know the stock type ID you can fetch the Stock type object for that directly from /api/stocktype/<int:stocktype_id>.json.

For example, to fetch the record for Stowford Press, you can fetch from /api/stocktype/10.json:

{
  "type": "stocktype",
  "key": "stocktype/10",
  "id": 10,
  "department": {
    "type": "department",
    "id": 35,
    "description": "Keg Cider",
    "notes": null
  },
  "manufacturer": "Westons",
  "name": "Stowford Press",
  "abv": "4.5",
  "fullname": "Westons Stowford Press (4.5% ABV)",
  "price": "4.50",
  "logo": "/media/emf/product-logos/f584a1ee8a3dafd443aaa6d991c8e18c7e3febf483ff1edad730691dec881ff1.png",
  "tasting_notes": "<p>A refreshing medium-dry sparkling cider that is bursting with the delicious flavour of crisp cider apples.</p>",
  "base_units_bought": "704.0",
  "base_units_remaining": "704.0",
  "base_unit_name": "pint",
  "sale_unit_name": "pint",
  "sale_unit_name_plural": "pints",
  "base_units_per_sale_unit": "1.0",
  "stock_unit_name": "pint",
  "stock_unit_name_plural": "pints",
  "base_units_per_stock_unit": "1.0"
}

Locations

/api/locations.json lists all of the stock line locations at the bar and cybar. These can be used to filter stocklines.

Example:

{
  "locations": [
    "Back bar",
    "Bar",
    "Counter",
    "Fridge",
    "Null Sector",
    "Optics (main bar)",
    "Optics (Null Sector)",
    "SpaceBAR"
  ]
}

/api/locations_display.json lists all of the stock line locations at the bar and cybar, along with their corresponding Location object.

Example:

{
  "locations": {
    "Back bar": {
      "sort": 1,
      "slug": "robotarms",
      "name": "Robot Arms",
      "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
    },
    "Bar": {
      "sort": 1,
      "slug": "robotarms",
      "name": "Robot Arms",
      "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
    },
    "Counter": {
      "sort": 1,
      "slug": "robotarms",
      "name": "Robot Arms",
      "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
    },
    "Fridge": {
      "sort": 1,
      "slug": "robotarms",
      "name": "Robot Arms",
      "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
    },
    "Null Sector": {
      "sort": 2,
      "slug": "cybar",
      "name": "Cybar",
      "maplink": "https://map.emfcamp.org/#21.54/52.0435004/-2.3767086"
    },
    "Optics (main bar)": {
      "sort": 1,
      "slug": "robotarms",
      "name": "Robot Arms",
      "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
    },
    "Optics (Null Sector)": {
      "sort": 2,
      "slug": "cybar",
      "name": "Cybar",
      "maplink": "https://map.emfcamp.org/#21.54/52.0435004/-2.3767086"
    },
    "SpaceBAR": {
      "sort": 3,
      "slug": "spacebar",
      "name": "SpaceBAR",
      "maplink": "https://map.emfcamp.org/#21.97/52.0437675/-2.37703993"
    }
  }
}

Stock lines

/api/stocklines.json lists all of the stock lines.

By default it returns the “brief” variant of the StockLine object. You can request full StockLine objects by setting the “output” query parameter to “full”; please be aware that this can be an expensive query and you should not use it to poll! Subscribe to updates using the websocket interface instead, or use MQTT.

You can restrict the output to stock lines of a particular type using the “type” query parameter, and to a particular location using the “location” query parameter. For example:

/api/stocklines.json?type=regular&location=Bar
/api/stocklines.json?type=regular&location=Null%20Sector

You can restrict the output to stock lines that start with a particular string using the “startswith” query parameter, and to exact matches using the “name” parameter.

Example output for location=Bar:

{
  "stocklines": [
    {
      "type": "stockline-brief",
      "key": "stockline/119",
      "id": 119,
      "name": "Cider 1",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/120",
      "id": 120,
      "name": "Cider 2",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/121",
      "id": 121,
      "name": "Cider 3",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/100",
      "id": 100,
      "name": "Pump 1",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/101",
      "id": 101,
      "name": "Pump 2",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/102",
      "id": 102,
      "name": "Pump 3",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/103",
      "id": 103,
      "name": "Pump 4",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/104",
      "id": 104,
      "name": "Tap 1",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/105",
      "id": 105,
      "name": "Tap 2",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/106",
      "id": 106,
      "name": "Tap 3",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/107",
      "id": 107,
      "name": "Tap 4",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/108",
      "id": 108,
      "name": "Tap 5",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/109",
      "id": 109,
      "name": "Tap 6",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/184",
      "id": 184,
      "name": "Tap 7",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/185",
      "id": 185,
      "name": "Tap 8",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/188",
      "id": 188,
      "name": "Tap C",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    },
    {
      "type": "stockline-brief",
      "key": "stockline/186",
      "id": 186,
      "name": "Tap L",
      "location": "Bar",
      "location_display": {
        "sort": 1,
        "slug": "robotarms",
        "name": "Robot Arms",
        "maplink": "https://map.emfcamp.org/#19.72/52.0413739/-2.3776123"
      },
      "note": "",
      "linetype": "regular"
    }
  ]
}

Null Sector bar / “Cybar”

The Null Sector bar sells the same stock as the main bar, with a couple of exceptions:

The beers and ciders on tap are different: fetch the current selection using /api/cybar-on-tap.json instead of /api/on-tap.json, or filter for “location=Null Sector” using /api/stocklines.json
Although the selection of spirits is the same, the individual bottles are necessarily different! Use /api/stocklines.json filtering for “location=Optics (Null Sector)” to retrieve the details specific to Null Sector

All other stock (wines, cans, bottles, soft drinks) is not tracked separately between the bars.

Web socket

You can connect to the web socket at wss://bar.emf.camp/websocket/

Once connected, you can subscribe to a key by sending the string SUBSCRIBE key, for example SUBSCRIBE stockline/107.

You can unsubscribe from a key by sending the string UNSUBSCRIBE key. You will not receive a response. If an update to that key was already on the way to you, you may still receive it even after unsubscribing.

Shortly after you subscribe to a key, you will be sent the corresponding object. If the system does not know about that object, you will be sent an object with type “not present”. The subscription will remain in place, and if the object is subsequently created you will receive it. (This is most likely to happen if the till server reboots: the service that responds to websocket requests may finish starting up before the service that forwards changes in state from the till database to the object store.)

Whenever the object changes state, you will receive an updated copy.

Web socket objects

All the objects mentioned above that have a key property can be subscribed to over the web socket.

Additionally, the following objects are only available over the web socket.

Totals by Unit

Key: totals/by-unit

This object gives the amounts sold broken down by Unit, where Unit is one of the following:

187ml can
200ml bottle
200ml can
250ml can
25ml measure
330ml can
375ml can
440ml can
500ml bottle
500ml can
568ml can
Wine bottle
Pint (from carton)
Packet
Pint (draught)

The amount sold is given as a Decimal. If the amount sold is zero, the Unit is omitted.

Example:

{
  "type": "totals by unit",
  "key": "totals/by-unit",
  "units": {
    "330ml can": "1.0"
  }
}

Cups re-used

Key: totals/cups-re-used

This object gives the number of cups that have been brought back to the bar to be re-filled. (When someone brings a cup to the bar to be filled with their drink, rather than take a fresh cup from our supply, we offer a small discount. This event we are paying a small amount to hire re-usable plastic cups, but a larger amount for each one actually used and requiring cleaning.)

This object is not updated in real-time. Instead, an update is published every minute.

Example:

{
  "type": "cups re-used",
  "key": "totals/cups-re-used",
  "count": 1
}

MQTT

All the objects that can be subscribed to over the websocket will also be published over MQTT, as bar/{key} (eg. bar/stockline/100). The “retain” flag will be set.

If a key is removed, a message with a zero length payload will be published (to remove the retained data) and then a “Not present” object will be sent without the “retain” flag set.

Check out the MQTT broker page for details on how to connect.

Note that the prefix has changed for 2026; it was emf/bar/ in 2024.

Last modified July 17, 2026: Remove the pre-event warning message (4fa38bf)