NetworkDesign: Difference between revisions

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* <i>Protocol version ( 1 byte )

* Type of Message ( 1 byte )

* Client ID ( 4 bytes )

Each message is held in one or more UDP Packets and the UDP Packet format is as follows: <br>

<b>1st UDP Packet is composed of:</b>

* <i>Total number of packets (1 byte)

* Type of Message (1 byte)

* Client ID (4 bytes)

<b>All other UDP Packets making up the one message are composed of:</b>

* Signature of the message (2 bytes)

* Rest of Message (up to 1497 bytes)</i>

Messages are sent from the Server by simply serializing them. So the message itself contains the protocol version, the type of message and the Client id.

Receiving the message is a bit more complex. First we need to determine that we are running a compatible version of the protocol by comparing the protocol version with the expected version in the message. Once we have agreed that the protocol is compatible we read the type of message and we ask the Message Factory ( see [[RolePlayingDesign]]) to build an object of that type with the corresponding data. Once the message is built we simply store it in a queue of incoming messages waiting to be processed.

The Network Manager is our router that sends and receives messages to and from the network. The manager exposes the interfaces that allow:

* Reading a message from the network

That is the basic idea of the Network Manager; however, the manager gets a bit more complex as a result of the need to support Server to Client messages that are bigger than one UDP package. Note that the manager just sends the stream of packets once and doesn't confirm if any of the messages are received. Please refer to [[NetworkDesign#UDP_Packet_Format | UDP Packet Format]] for more info about it.

To communicate, the Client and Server of Marauroa use a stream of UDP packets. The message system belongs to the marauroa.common.net package, so refer to the code for a detailed knowledge of the system.

Let's discuss in detail each message type.

This Login Message is sent from the Client to the Server to request the RSA public key of the server.

This Login Message is sent from the Server to the Client in response to a key request. It is composed of two bytes arrays. The first one contains the value of 'n', and the second the value of 'e'.

This is the first real action of authentification from the client. It computes a nonce (a random number) and sends a hash of its nonce to the server. This message contains the hash as a bytes array.

The server responds to the client promise by computing a nonce and sending it in this message. This message contains the nonce as a bytes array.

The client now sends its nonce, its username and the value Crypt(xor(xor(client nonce, server nonce), password). This message contains 3 fields. The first one is a bytes array containing the client nonce, the second one a string containing the username and the third one a bytes array containing the encrypted password. On reception, the server checks that the hash he received at first is the hash of the nonce he just received. It then decodes the password field, and having the value of the client nonce and its nonce, it gets the value of the password. If the username/password combination is correct then the Server must send a Login ACK Message to indicate to the Client that the message has been correctly processed. However, if the username/password is wrong the Server will send a Login NACK (Not ACKnoledge).

The LoginACK Message is sent from the Server to the Client to indicate that the login process has been completed correctly and that it can proceed to the next step. It has no params.

The LoginNACK Message is sent from the Server to the Client to tell the Client that its login message is incorrect because either the username or password is wrong or because Server has decided to reject the login request, e.g. if the Server is full or because the IP is banned.

The message is composed of: Message indicating the resolution.

The CharacterList Message is sent from the Server to the Client to give the Client a choice of character to play with. This feature models the behavior of having several characters associated with a single account ( see [[DesignOverview#What_is_Marauroa.3F | the Marauroa Feature List]] ).

Each character name must be unique at Server level, and it is assigned when the character is created.

The Server Info Message is sent from the Server to the Client to tell the Client about what Server is running, and details on how to inform the Server administrator of any problems (e.g. their email address).

The message is composed of: A List of strings of the type "attribute=value"

The ChooseCharacter Message is sent from the Client to the Server to indicate what character the user wishes to play the game with.

Once a character is chosen, the only way to choose a new one is by logging out and logging in again.

The Choose Character ACK Message is sent from the Server to the Client to notify the Client that the character has been chosen.

We need this value to track our own character.

The Choose Character NACK Message is sent from the Server to the Client to notify the Client that the character has not been chosen. This also implies to the Client that it should send another ChooseCharacter Message.

It has no params.

The Logout Message is sent from the Client to the Server to indicate that it wants to finish the session. It has no params.

If the Client can logout the Server will send a Logout ACK Message and the Client can safely close the connection, but if the Server sends a Logout NACK Message, the Client should keep playing as disconnecting at that moment will leave its avatar in the game uncontrolled ( idle ).

The Logout ACK Message is sent from the Server to the Client to notify the Client that the logout has been accepted.

It has no params.

The Logout NACK Message is sent from the Server to the Client to tell the Client that the logout has not been accepted, possibly because something related to the RP entity, for example, combat is in progress.

It has no params.

The Action message is sent from the Client to the Server to notify the Server of the Clients desire to execute an action. The message is simply composed of a single action.

The Action ACK is sent from the Server to the Client to identify that the action has been received in the Server. It doesn't acknowledge that the action has been accepted by the RP Manager, it just means that the action successfully arrived at the Server.

It has 1 param: action_id - is used to identify to which action you referred. In Marauroa you can command several actions per turn.

The Perception message is a message sent from the Server to the Client to notify the Client about changes to the objects that exist near it. The message is based on the idea explained in the [[RolePlayingDesign#Perceptions| Delta Perception document]].

Read the Delta perception algorithm to understand what it is for.

The perception ACK message is sent from the Client to the Server. We use this message to inform the Server that the Client is still there and listening. It has no params.

The TransferREQ message is a message sent from the Server to the Client to notify the Client of the server's desire to send content useful for game play.

The message is composed of: An array of TransferContent objects containing the name of each resource, its timestamp (or checksum) and if the resource is cacheable or not.

The TransferACK message is a message sent from the Client to the Server to notify the Server about what of the given TransferContent elements recieved from TransferREQ should be sent.

The message is composed of: An array of TransferContent objects containing all the name of each resource and a flag indicating ack or not.

The Transfer message is a message sent from the Server to the Client to send the Client content useful for the game where play will happen.

The message is composed of: An array of TransferContent objects containing all the name of each resource, its timestamp, a flag indicating if the resource is cacheable or not and a byte array with the content itself.

[[Category:Marauroa]]