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Game Web-Socket messages

ws://localhost:8080/ws/games/1 connects a client to the game's web-socket JSON stream.

When connection has been established, the server:

  • Initializes a game session
  • Returns the map size
  • Returns all objects in the game
  • Creates a snake
  • Returns an identifier of the snake
  • Starts pushing updates into the stream

Game primitives

There are a few game primitives:

  • Direction: "north", "west", "south", "east"
  • Dot: [x, y]
  • Dot list: [[x, y], [x, y], [x, y], [x, y], [x, y], [x, y]]
  • Rectangle: [x, y, width, height]

Game objects

Game objects:

  • Snake: 
    {
  "type": "snake",
  "id": 12,
  "dots": [[4, 3], [3, 3], [2, 3]]
}
  • Apple: 
    {
  "type": "apple",
  "id": 123,
  "dot": [3, 2]
}
  • Corpse: 
    {
  "type": "corpse",
  "id": 142,
  "dots": [[3, 2], [3, 1], [3, 0]]
}
  • Mouse: 
    {
  "type": "mouse",
  "id": 123,
  "dot": [3, 2],
  "direction": "south"
}
  • Watermelon: 
    {
  "type": "watermelon",
  "id": 123,
  "dots": [[4, 4], [4, 5], [5, 4], [5, 5]]
}
  • Wall: 
    {
  "type": "wall",
  "id": 351,
  "dots": [[4, 2], [2, 1], [2, 3]]
}

Game messages

There are input and output game messages.

Output messages

Output messages are sent by server to client.

Example:

{
  "type": <output_message_type>,
  "payload": <output_message_payload>
}

Types:

  • game - contains game events. Game events have a type and a payload:

    {
  "type": "game",
  "payload": {
    "type": <game_event_type>,
    "payload": <game_event_payload>
  }
}

    Game events contain information about creating, updating, deleting of game objects on the map.

  • player - contains player specific information. Player messages have a type and a payload:

    {
  "type": "player",
  "payload": {
    "type": <player_message_type>,
    "payload": <player_message_payload>
  }
}

    Player messages contain user specific information such as user notifications, errors, snake identifiers, etc.

  • broadcast - contains broadcasted messages (type string):

    {
  "type": "broadcast",
  "payload": "Surprise!"
}

Game events

Output message type: game

Game event types:

  • error - contains description (string) of the error

  • create - contains the created object:

    {
  "type": "game",
  "payload": {
    "type": "create",
    "payload": {
      "id": 41,
      "dots": [[9, 9], [9, 8], [9, 7]],
      "type": "snake"
    }
  }
}

  • delete - contains the deleted object

  • update - contains the updated object

    • When the snake moves: 
      {
  "type": "game",
  "payload": {
    "type": "update",
    "payload": {
      "id": 123,
      "dots": [[19, 6], [19, 7], [19, 8]],
      "type": "snake"
    }
  }
}
    • An update of a corpse: 
      {
  "type": "game",
  "payload": {
    "type": "update",
    "payload": {
      "id": 142,
      "dots": [[6, 17], [6, 18], [6, 19], [7, 19], [8, 19], [8, 20], [8, 21]],
      "type": "corpse"
    }
  }
}

  • checked - contains an object which was checked by another game object (deprecated)

Player messages

Output message type: player

Player's messages types:

  • size - contains size of the map (object):

    {
  "type": "player",
  "payload": {
    "type": "size",
    "payload": {
      "width":255,
      "height":255
    }
  }
}

  • snake - contains an integer: a snake identifier

  • notice - contains a notification (string)

    {
  "type": "player",
  "payload": {
    "type": "notice",
    "payload": "welcome to snake-server!"
  }
}

  • error - contains a string: error description

    {
  "type": "player",
  "payload": {
    "type": "error",
    "payload": "something went wrong!"
  }
}

  • countdown - contains an integer: the number of seconds to wait

    {
  "type": "player",
  "payload": {
    "type": "countdown",
    "payload": 5
  }
}

  • objects - contains a list of all objects in the game to initialize the map on the client side

    {
  "type": "player",
  "payload": {
    "type": "objects",
    "payload": [
      {
        "id": 21,
        "dot": [17, 18],
        "type": "apple"
      },
      {
        "id": 63,
        "dots": [[24, 24], [25, 24], [26, 24]],
        "type": "corpse"
      }
    ]
  }
}

Broadcast messages

Output message type: broadcast

Contains a string - a group notification to all players in the game.

Example:

{
  "type": "broadcast",
  "payload": "hello world!"
}

Input messages

Input messages are sent by client to server.

Input message structure:

{
  "type": <input_message_type>,
  "payload": <input_message_payload>
}

Input message size is limited: maximum 128 bytes

Input message types:

  • snake - snake commands
  • broadcast - short phrases or emojis to be broadcasted in the game

Snake input message

A snake input message contains a command which sets snake's movement direction.

Accepted commands:

  • north - to the north 
    {
  "type": "snake",
  "payload": "north"
}
  • east - to the east 
    {
  "type": "snake",
  "payload": "east"
}
  • south - to the south 
    {
  "type": "snake",
  "payload": "south"
}
  • west - to the west 
    {
  "type": "snake",
  "payload": "west"
}

Broadcast input message

A broadcast input message contains a short message to all players in the game.

Examples:

  • Text: hello! 
    {
  "type": "broadcast",
  "payload": "hello!"
}
  • Smile: ;) 
    {
  "type": "broadcast",
  "payload": ";)"
}