snake-server

README

Snake-Server

Snake-Server is the server for online arcade game - snake.

Table of contents

• Game rules
• Basic usage
• Installation
  • Download and install binary
  • Build and install latest server
  • Pull server image from docker-hub
  • Build and install server of specific version from source code
  • Deploy the server with ansible playbook
• CLI arguments
• Clients
• API description
  • API requests
  • API errors
• Game Web-Socket messages description
  • Game primitives
  • Game objects
  • Output messages
  • Input messages
• License

Game rules

• A player controls a snake.
• The task of the game is to grow the biggest snake.
• In order to achieve the goal players may eat apples, watermelons, small snakes and remains of dead snakes of other players.
• If a snake hits a wall the snake dies and the player starts again with a new small snake.
• A snake may eat another snake if it's length greater or equal to the square of length of the second one.

Screenshot:

Basic usage

Start snake-server:

• Using binary:

  snake-server --enable-web
  

• Or docker:

  docker run --rm -p 8080:8080 ivan1993spb/snake-server --enable-web
  

Open in a browser http://localhost:8080/.

Installation

There are many options to get Snake-Server. You can download the server binary, build the server from the source or pull the server docker image. See below.

Download and install binary

You can download binary from releases page: https://github.com/ivan1993spb/snake-server/releases/latest

Or using curl:

• Setup variables VERSION, PLATFORM (darwin, linux or windows) and ARCHITECTURE (386 or amd64)
• Use curl to download snake-server binary: curl -sL https://github.com/ivan1993spb/snake-server/releases/download/${VERSION}/snake-server-${VERSION}-${PLATFORM}-${ARCHITECTURE}.tar.gz | tar xvz

Then:

• Rename binary to snake-server: mv snake-server-${VERSION}-${PLATFORM}-${ARCHITECTURE} snake-server
• Make binary file executable with chmod +x snake-server
• Move snake-server to /usr/local/bin/: mv snake-server /usr/local/bin/
• Use snake-server -h to see the usage information

Build and install latest server

In order to build Snake-Server you need installed Go compiler (version 1.6+ is required).

The simpliest way to install the latest Snake-Server is to run go-get command to load the source code from the master branch, build and install snake-server into ${GOPATH}/bin directory:

go get -u github.com/ivan1993spb/snake-server
snake-server -h

Pull server image from docker-hub

Firstly, you need installed docker: use fast installation script.

See snake-server docker-hub repository: https://hub.docker.com/r/ivan1993spb/snake-server.

Choose image tag from the tags list.

• Use docker pull ivan1993spb/snake-server to pull server image from docker-hub
• docker run --rm --net host --name snake-server ivan1993spb/snake-server to start server
• docker run --rm ivan1993spb/snake-server -h for usage information

Add alias for running snake-server container:

• alias snake-server="docker run --rm -it --net host --name snake-server ivan1993spb/snake-server:latest"
• snake-server --help

Build and install server of specific version from source code

You may get Snake-Server source code of specific version by curl command:

• mkdir -p ${GOPATH}/src/github.com/ivan1993spb/snake-server
• Download and extract source code curl -sL https://github.com/ivan1993spb/snake-server/archive/${VERSION}.tar.gz | tar xvz --strip 1 -C ${GOPATH}/src/github.com/ivan1993spb/snake-server
• cd ${GOPATH}/src/github.com/ivan1993spb/snake-server

Then there are three options how to build the server from sources:

• Build the server binary using Go compiler
• Build the server binary using Docker
• Build the Docker image

Build the server binary using Go compiler

In order to build Snake-Server you need installed Go compiler (version 1.6+ is required).

If you have appropriate Go compiler, use:

• make VERSION=${VERSION} BUILD=custom
• make install VERSION=${VERSION} BUILD=custom

Then:

• Use snake-server -h to see the usage information
• snake-server to start the server

Build the server binary using Docker

If you have Docker, use:

• make go/build VERSION=${VERSION} BUILD=custom
• Move snake-server to /usr/local/bin/: mv snake-server /usr/local/bin/

Then:

• Use snake-server -h to see the usage information
• snake-server to start the server

Build Docker image

In order to build Snake-Server Docker image you need installed Docker (version 17.05+ is required)

Use command make docker/build to build image.

Then:

• Use docker run --rm ivan1993spb/snake-server -h to see the usage information
• docker run --rm ivan1993spb/snake-server to start the server

Deploy the server with ansible playbook

Snake's playbook repository - here.

git clone https://github.com/ivan1993spb/snake-ansible.git

CLI arguments

Use snake-server --help for help info.

Arguments:

• --address - string - address to serve (default: :8080). For example: :8080, localhost:7070
• --conns-limit - int - opened web-socket connections limit (default: 1000)
• --groups-limit - int - game groups limit for server (default: 100)
• --enable-web - bool - enable web client (default: false)
• --enable-broadcast - bool - enable broadcasting API method (default: false)
• --log-json - bool - set this flag to use JSON log format (default: false)
• --log-level - string - set log level: panic, fatal, error, warning (warn), info or debug (default: info)
• --seed - int - random seed (default: the number of nanoseconds elapsed since January 1, 1970 UTC)
• --tls-cert - string - path to certificate file
• --tls-enable - bool - flag: enable TLS
• --tls-key - string - path to key file

Clients

There is an embedded JavaScript client for the server. You may enable the client using cli flag --enable-web.

You are welcome to create your own client using described API.

Some samples you can see here:

• VueJS client repo: https://github.com/ivan1993spb/snake-lightweight-client
• Python client repo: https://github.com/ivan1993spb/snake-client

API description

All API methods provide JSON format. If errors are occurred methods return HTTP statuses and JSON formatted error objects. See swagger.yml for details. Also, see API curl examples below.

API requests

Request POST /api/games

Request creates a game and returns JSON game object.

curl -s -X POST -d limit=3 -d width=100 -d height=100 http://localhost:8080/api/games | jq
{
  "id": 1,
  "limit": 3,
  "count": 0,
  "width": 100,
  "height": 100,
  "rate": 0
}

Request GET /api/games

Request returns an information about all games on server.

curl -s -X GET http://localhost:8080/api/games | jq
{
  "games": [
    {
      "id": 1,
      "limit": 10,
      "count": 0,
      "width": 100,
      "height": 100,
      "rate": 0
    },
    {
      "id": 2,
      "limit": 10,
      "count": 0,
      "width": 100,
      "height": 100,
      "rate": 0
    }
  ],
  "limit": 100,
  "count": 2
}

Request GET /api/games/{id}

Request returns an information about a game by id.

curl -s -X GET http://localhost:8080/api/games/1 | jq
{
  "id": 1,
  "limit": 10,
  "count": 0,
  "width": 100,
  "height": 100,
  "rate": 0
}

Request DELETE /api/games/{id}

Request deletes a game by id if there is not players in the game.

curl -s -X DELETE http://localhost:8080/api/games/1 | jq
{
  "id": 1
}

Request POST /api/games/{id}/broadcast

Request sends a message to all players in selected game. Returns true on success. Request body size is limited: maximum 128 bytes

curl -s -X POST -d message=text http://localhost:8080/api/games/1/broadcast | jq
{
  "success": true
}

If request method is disabled, you will get 404 error. See CLI arguments.

Request GET /api/games/{id}/objects

Request returns all objects on map of a game with passed identifier.

curl -s -X GET http://localhost:8080/api/games/1/objects | jq
{
  "objects": [
    {
      "id": 99,
      "dots": [
        [0, 2],
        [1, 2],
        [0, 0],
        [1, 0],
        [1, 1],
        [2, 1]
      ],
      "type": "wall"
    },
    {
      "id": 124,
      "dot": [18, 16],
      "type": "apple"
    },
    {
      "id": 312,
      "dots": [
        [9, 17],
        [10, 17],
        [9, 18],
        [10, 18]
      ],
      "type": "watermelon"
    }
  ]
}

Request GET /api/capacity

Request returns the server instance capacity metric. Capacity is the number of opened web-socket connections divided by the number of allowed connections for the server instance.

curl -s -X GET http://localhost:8080/api/capacity | jq
{
  "capacity": 0.02
}

Request GET /api/info

Request returns the common information about the server: author, license, version, build.

curl -s -X GET http://localhost:8080/api/info | jq
{
  "author": "Ivan Pushkin",
  "license": "MIT",
  "version": "v4.0.0",
  "build": "85b6b0e"
}

Request GET /api/ping

Request returns pong response from the server.

curl -s -X GET localhost:8080/api/ping | jq
{
  "pong": 1
}

API errors

API methods return error status codes (400, 404, 500, etc.) with error description in JSON format: {"code": error_code , "text": error_text }. JSON error structure can contains additional fields.

Example:

curl -s -X GET http://localhost:8080/api/games/1 -v | jq
*   Trying 127.0.0.1...
* Connected to localhost (127.0.0.1) port 8080 (#0)
> GET /api/games/0 HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.47.0
> Accept: */*
>
< HTTP/1.1 404 Not Found
< Server: Snake-Server/v3.1.1-rc (build 85b6b0e)
< Vary: Origin
< Date: Wed, 20 Jun 2018 12:24:44 GMT
< Content-Length: 44
< Content-Type: application/json; charset=utf-8
<
{ [44 bytes data]
* Connection #0 to host localhost left intact
{
  "code": 404,
  "text": "game not found",
  "id": 1
}

Game Web-Socket messages description

The request ws://localhost:8080/ws/games/1 connects to the game Web-Socket JSON stream by game identificator.

When connection has established, handler:

• Initializes the game session
• Returns the playground size
• Returns all objects on playground
• Creates the snake
• Returns the snake identifier
• Pushes game events and objects to web-socket stream

There are input and output web-socket messages.

Game primitives

To explain game objects there is JSON 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]]
  }
  

• 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]]
  }
  

Output messages

Output messages - when server sends to the client a data.

Output message structure:

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

Output message can be type of:

• game - message payload contains a game events. Game events has type and payload: {"type": game_event_type, "payload": game_event_payload}. Game events contains information about creation, updation, deletion of game objects on playground
• player - message payload contains a player specified info. Player messages has type and payload: {"type": player_message_type, "payload": player_message_payload}. Player messages contains user specific game information: user notifications, errors, the snake identifier, etc.
• broadcast - message payload contains a group broadcast messages. Payload of output message of type broadcast contains string message

Examples:

{
  "type": "player",
  "payload": ...
}
{
  "type": "game",
  "payload": ...
}
{
  "type": "broadcast",
  "payload": ...
}

Game events

Output message type: game

Game events types:

• error - a payload contains string: error description
• create - a payload contains game object that was created
• delete - a payload contains game object that was deleted
• update - a payload contains game object that was updated
• checked - a payload contains game object that was checked by another game object

Examples:

{
  "type": "game",
  "payload": {
    "type": "create",
    "payload": {
      "id": 41,
      "dots": [[9, 9], [9, 8], [9, 7]],
      "type": "snake"
    }
  }
}
{
  "type": "game",
  "payload": {
    "type": "update",
    "payload": {
      "id": 123,
      "dots": [[19, 6], [19, 7], [19, 8]],
      "type": "snake"
    }
  }
}
{
  "type": "game",
  "payload": {
    "type": "checked",
    "payload": {
      "id": 421,
      "dots": [[6, 17], [6, 18], [6, 19], [7, 19], [8, 19], [8, 20], [8, 21]],
      "type": "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"
    }
  }
}

Player messages

Output message type: player

Player messages types:

• size - a payload contains playground size object: {"width":10,"height":10}
• snake - a payload contains string: snake identifier
• notice - a payload contains string: a notification
• error - a payload contains string: error description
• countdown - a payload contains int: number of seconds for countdown
• objects - a payload contains a list of all objects on the playground. The message contained objects is necessary to initialize the map on client side

Examples:

{
  "type": "player",
  "payload": {
    "type": "notice",
    "payload": "welcome to snake-server!"
  }
}
{
  "type": "player",
  "payload": {
    "type": "size",
    "payload": {
      "width":255,
      "height":255
    }
  }
}
{
  "type": "player",
  "payload": {
    "type": "objects",
    "payload": [
      {
        "id": 21,
        "dot": [17, 18],
        "type": "apple"
      },
      {
        "id": 63,
        "dots": [[24, 24], [25, 24], [26, 24]],
        "type": "corpse"
      }
    ]
  }
}
{
  "type": "player",
  "payload": {
    "type": "countdown",
    "payload": 5
  }
}

Broadcast messages

Output message type: broadcast

Payload of output message of type broadcast contains string - a group notice that sends to all players in game group.

Example:

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

Input messages

Input messages - when client sends to server an information.

Input message structure:

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

Input message types:

• snake - when player sends a game command in message payload to control snake
• broadcast - when player sends a short phrase or emoji to broadcast it for players in game

Input message size is limited: maximum 128 bytes

Snake input message

Snake input message contains game command. Game command sets snake direction if it possible.

Accepted commands:

• north - sets snake direction to north
• east - sets snake direction to east
• south - sets snake direction to south
• west - sets snake direction to west

Examples:

{
  "type": "snake",
  "payload": "north"
}
{
  "type": "snake",
  "payload": "east"
}
{
  "type": "snake",
  "payload": "south"
}
{
  "type": "snake",
  "payload": "west"
}

Broadcast input message

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

Examples:

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

License

See LICENSE.