Messages Exchange

The messages exchange between the client and the server it's build on the interface IService. Every service provided by the server must implements this interface. In the additional package messages there are more specific classes who create the server messages.

Every message use the JSON format. More specifically we used org.json library.

Now we will see each service message in great detail.

Register

Through the client you can create an account on the server. A registration message from the client who comply with the fields rules specified in FieldsValues has always the following fields:

{"service":"register","password":"MY_PASSWORD","email":"MY_EMAIL","username":"MY_USERNAME"}

If there are no errors the server returns the following response:

{"errors":{},"service":"register","noErrors":true}

If a field is wrong, an error occurs:

• Invalid username

  • Too short

    {"errors":{"username":["short"]},"service":"register","noErrors":false}
    

  • Too long

    {"errors":{"username":["long"]},"service":"register","noErrors":false}
    

  • Invalid character

    {"errors":{"username":["invalidChar"]},"service":"register","noErrors":false}
    

  • It not contains a needed character (actually not implemented)

    {"errors":{"username":["invalidChar"]},"service":"register","noErrors":false}
    

  • Already used

    {"errors":{"username":["alreadyUsed"]},"service":"register","noErrors":false}
    

• Invalid password

  • Too short

    {"errors":{"password":["short"]},"service":"register","noErrors":false}
    

  • Too long

    {"errors":{"password":["long"]},"service":"register","noErrors":false}
    

  • Invalid character (actually not implemented)

    {"errors":{"password":["invalidChar"]},"service":"register","noErrors":false}
    

  • It not contains a needed character

    {"errors":{"password":["invalidChar"]},"service":"register","noErrors":false}
    

• Invalid email

  • Invalid format

    {"errors":{"email":["invalidField"]},"service":"register","noErrors":false}
    

  • Invalid domain

    {"errors":{"email":["invalidDomain"]},"service":"register","noErrors":false}
    

  • Already used

    {"errors":{"email":["alreadyUsed"]},"service":"register","noErrors":false}
    

Multiple errors can obviously occur, like the following example:

{"errors":{"username":["long"],"email":["invalidField"],"password":["short","invalidChar"]},"service":"register","noErrors":false}

Login

A login client request has always the following format:

{"service":"login","password":"PASSWORD","username":"USERNAME"}

If all the fields are ok the response is the following:

{"username":"USERNAME","service":"login","hashcode":HASHCODE,"noErrors":true}

In which the hashCode is a login-created code who identify a user. Any user has a different account that change at any login. The hashCode is generated in OnlineUser.

If a field is wrong, the server send always this response:

{"username":"marx","service":"login","hashcode":0,"noErrors":false}

This error can occur when:

• The password linked to the username is wrong
• The username is not registered
• The user is already signed in

Rooms

When the login phase is completed, the client automatically send to the server a request for the list of the available rooms:

{"serviceType":"list","service":"rooms","username":"USERNAME","hashcode":HASHCODE}

The server respond with the list. For every room are specified the number of the users actually in the room (currentPlayers), and the maximum number of users in that room (maxPlayers). For example:

{"service":"rooms","list":{"ROOM1 ":{"currentPlayers":X¹,"maxPlayers":Y¹},"ROOM2 ":{"currentPlayers":X²,"maxPlayers":Y²}},"serviceType":"list","noErrors":true}

If there are no rooms the server send an empty list:

{"service":"rooms","list":{},"serviceType":"list","noErrors":true}

A user can create a room. In this case the client send the following message:

{"service":"rooms","username":"USERNAME","hashcode":HASHCODE,"serviceType":"create","name":"NAME_OF_THE_ROOM"}

The response of the server is the list of available rooms. But some errors can occur in the creation of a room:

• The chosen room's name is already used

  {"errors":{"errors":["createErrorAlreadyPresent"]},"service":"rooms","serviceType":"create","noErrors":false}
  

• The chosen room's name is invalid (too short, too long, etc.)

  {"errors":{"errors":["createErrorInvalidname"]},"service":"rooms","serviceType":"create","noErrors":false}
  

CurrentRoom

When a user join a room, the client send this message:

{"service":"rooms","username":"USERNAME","hashcode":HASHCODE,"serviceType":"join","name":"NAME_OF_THE_ROOM"}

If the room is available, the server send this response:

{"result":true,"name":"NAME_OF_THE_ROOM","service":"rooms","serviceType":"join","noErrors":true}

Then the client ask for some room's information (like the already presents players):

{"service":"currentRoom","username":"USERNAME","hashcode":HASHCODE,"serviceType":"playerList","name":"NAME_OF_THE_ROOM"}

The response from the server is the following:

{"maxPlayers":X,"service":"currentRoom","team":[{"teamColor":COLOR¹,"name":"Team 1","list":[{"username":"USERNAME1"},{"username":"USERNAME2"}]},{"teamColor":COLOR²,"name":"Team 2","list":[{"username":"USERNAME3"},{"username":"USERNAME4"}]}],"serviceType":"playerList"}

In this example there are two teams, and every team has two players. In the following example there is only one team with three single players:

{"maxPlayers":X,"service":"currentRoom","team":[{"teamColor":COLOR,"name":"Team 1","list":[{"username":"USERNAME1"},{"username":"USERNAME1"},{"username":"USERNAME3"}]}],"serviceType":"playerList"}

Some errors can occurs:

• Full room or non-existent room

  {"result":false,"name":"NAME_OF_THE_ROOM","service":"rooms","serviceType":"join","noErrors":false}
  

• If the user try to join a room who has already joined, the server do nothing, and responds with the previous explained messages.

Audio

When a room it's full, the game automatically starts, and the client send to the server the port chosen for the audio streaming:

{"service":"audio","username":"USERNAME","hashcode":HASHCODE,"audioPortClient":PORT,"name":"NAME_OF_THE_ROOM"}

The server responds with the server side port:

{"audioPortServer":PORT,"service":"audio"}

Game

In addition to the audio port, when a room it's full the client send to the server a request for the game map:

{"service":"game","username":"USERNAME","hashcode":HASHCODE,"serviceType":"map","name":"NAME_OF_THE_ROOM"}

Then the server send to the client the map:

{"height":"LENGTH_OF_THE_MAP","items":[{"position":"POSITION_ITEM¹","texture":"TEXTURE_ITEM¹","object":"ITEM¹","size":"SIZE_ITEM¹"},{"position":"POSITION_ITEM²","texture":"TEXTURE_ITEM²","object":"ITEM²","size":"SIZE_ITEM²"},{"position":"POSITION_ITEM³","texture":"TEXTURE_ITEM³","object":"ITEM³","size":"SIZE_ITEM³"}],"players":"SPAWN_POINT","width":"WIDTH_OF_THE_MAP","service":"game","serviceType":"map"}

In this example the map consists of three items.

If a user ask for a map of a room in which is not joined, the server send the map however, with no errors.

Before the game really starts, there is a loading phase. When the client it's ready it send to the server a message to say this:

{"service":"game","username":"USERNAME","hashcode":HASHCODE,"serviceType":"status","ready":true,"name":"NAME_OF_THE_ROOM"}

Then the client starts to send the position of the player in the map, to update other clients positions list:

{"position":{"z":Z,"y":Y,"x":X},"service":"game","username":"USERNAME","serviceType":"positions","direction":{"z":Z,"y":Y,"x":X},"name":"NAME_OF_THE_ROOM"}

The server responds with the positions of the other players:

{"players":[],"service":"game","serviceType":"positions"}