GServer

Note: This README is a work in progress 🛠️

A rudimentary TCP/UDP game server mimicking the architecture of Graal Online's GServer from the 90s-00s.

Projects

The repo is made up of the following projects:

• GServer.Server - the server to be connected to
• GServer.Client - the client that connects to the server
• GServer.Common - a class library used by both of the above projects. Contains shared code.

Networking

Packets are sent between the client and server to enable communication. Specific packets can carry data specific purposes, referred to as messages. A message has an ID that defines its type/purpose, as well as data related to its purpose.

The first byte of a message is used to denote its type, but no standard format is shared between messages for the data belonging to each message.

For example: when authenticating, the following message is used:

• Message ID (1 byte)
• Username length (1 byte)
• Username (x bytes, according to the username length)
• Password length (1 byte)
• Password (x bytes, according to the password length)

{message_id}{username_len}{username}{password_len}{password}

(see Messages section for this message and others' ASN.1 definitions)

All possible client and server message IDs can be found in GServer.Common/Networking/Enums/ClientPacketIn.cs (for packets processed by the client) or GServer.Common/Networking/Enums/ServerPacketIn.cs (for messages processed by the server)

Messages

The below lists ASN.1 definitions for each message exactly as they are intended to be send and received by the game client and server. All C# message definitons can be found in GServer.Common/Networking/Messages

AuthMessage

AuthMessage ::= SEQUENCE {
    messageId   INTEGER (0..255),
    usernameLen INTEGER (0..255),
    username    OCTET STRING (SIZE (0..usernameLen)),
    passwordLen INTEGER (0..255),
    password    OCTET STRING (SIZE (0..passwordLen))
}

AuthResponseMessage

AuthResponseMessage ::= SEQUENCE {
    messageId       INTEGER (0..255),
    isSuccessful    INTEGER (0..255),
    TODO implement CHOICE for conditional fields
}

ListServerResponseMessage (TODO)

ServerListingBlock ::= SEQUENCE {
    name        OCTET STRING (SIZE (50)),
    description OCTET STRING (SIZE (1000)),
    playercount INTEGER (0..65535),
    ip          OCTET STRING (SIZE (15)),
    port        INTEGER (0..65535),
    serverTier  INTEGER (0..255)
}

ServerListing ::= SEQUENCE {
    messageId           INTEGER (0..255),
    serverListingBlocks SEQUENCE OF ServerListingBlock
}