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NETWORK_PROTOCOL.md

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Network Communication

All binary communication over TCP sockets is done in network byte order (big endian).

Initial Connection

Establishing the initial connection between the client and the gameserver is done via the lobby server. The following sequence diagram illustrates a minimal sequence leading to an established connection. Connection Sequence Diagramm

Communication Between Client and Gameserver

Message Types

Each message starts with a message header consisting of the message type (uint8_t) and the payload size (uint16_t).

Value Message Type
0 Heartbeat
1 GridState
2 GameStart
3 EventBroadcast

Messages From Client to Server

  • For every frame that is divisible by 15, the client sends a message to the server that contains all input events that have happened since the last message and up until the current frame.

    Element Data Type Value
    message type uint8_t 0 (Heartbeat)
    payload size uint16_t 9 + 10 * <number of events>
    frame uint64_t the current frame (divisible by 15)
    number of events uint8_t number of events contained in the message (at least 0, at most 15)
    event key uint8_t <key>
    event type uint8_t <event_type> (OBPF_PRESSED or OBPF_RELEASED)
    event frame uint64_t <frame>
    more events...

  • If a new piece is spawned in a given frame, the client sends the complete grid state at this point in time to the server.

    Element Data Type Value
    message type uint8_t 1 (GridState)
    payload size uint16_t 228
    frame uint64_t the current frame
    grid contents uint8_t[10 * 22] tetromino type of each individual tetrion in the grid (OBPF_TETROMINO_TYPE_EMPTY, OBPF_TETROMINO_TYPE_I, OBPF_TETROMINO_TYPE_J, OBPF_TETROMINO_TYPE_L, OBPF_TETROMINO_TYPE_O, OBPF_TETROMINO_TYPE_S, OBPF_TETROMINO_TYPE_T, OBPF_TETROMINO_TYPE_Z)

Messages From Server to Clients

  • After the expected number of clients have connected, the server sends all clients informations about the start of the game.

    Element Data Type Value
    message type uint8_t 2 (GameStart)
    payload size uint16_t 17
    client id uint8_t <id of each individual client>
    start frame uint64_t 180 (subject to change)
    random seed uint64_t <random seed>

  • As soon as all heartbeat messages for a given frame (divisible by 15) have reached the server, the server sends all input commands of all clients during the last period to all clients.

    Element Data Type Value
    message type uint8_t 3 (EventBroadcast)
    payload size uint16_t 9 + <client count> * 2 + <total event count> * 10
    frame uint64_t <current frame> (divisble by 15)
    num clients uint8_t <client count>
    client id uint8_t <client id>
    num events for this client uint8_t <event count> (at least 1, at most 15)
    event key uint8_t <key>
    event type uint8_t <event_type> (OBPF_PRESSED or OBPF_RELEASED)
    event frame uint64_t <frame>
    more events...
    more clients...