Diarkis RUDP

Overview

Reliable User Datagram Protocol (RUDP) is an implementation of UDP communication where data delivery is guaranteed. Diarkis client can use RUDP to transmit data either in server communications or P2P communications, ensuring that crucial information necessary for game progression is reliably delivered to the other party. This page explains the specifications and settings of Diarkis RUDP.

Specifications of Diarkis RUDP

The combinations in which Diarkis RUDP can be established include server-client and client-client (P2P communication). Some features are only available in P2P communications.

In Diarkis RUDP, when data is received, an Acknowledgement (ACK) is returned to inform the sender of the data's arrival. If an ACK is not received within a specified timeframe, the Diarkis client will resend the same data. In this document, this timeframe is referred to as RetryInterval. Furthermore, if an ACK is not received after resending the data a specified number of times, the Diarkis client will disconnect the communication with the other party due to a timeout. In this document, this number of retries is referred to as RetryMaxCount.

Exclusively in P2P communications with RUDP, a sequence guarantee toggle feature is provided in addition to data delivery assurance. When sequence guarantee is enabled, it ensures that the data received by the application is in the order sent by the peer user. The Diarkis library will not pass data to the application until packets are received in the correct sequential order. If the sequence guarantee is disabled, the Diarkis library will pass packets to the application in the order they are received, and this order may vary due to network conditions or retransmission.

In server-client RUDP communication, the sequence guarantee is always enabled.

Configuration of Diarkis RUDP

Setting the RetryInterval

The RetryInterval can be adjusted using the following function:

udp.h

void SetSendRetryInterval(uint32_t minMs, uint32_t maxMs)

The RetryInterval starts at the time specified by minMs (milliseconds) and doubles each time the client resends until it reaches the time specified by maxMs. For example, if minMs=300ms, maxMs=1000ms, and RetryMaxCount is 5, the RetryInterval changes as 300ms, 600ms, 900ms, 1000ms, 1000ms. If the fifth resend times out, the client disconnects the communication.

By making the RetryInterval exponential, you can reduce the client's network processing load. If you wish to have a fixed RetryInterval, specify the same value for both minMs and maxMs to keep the RetryInterval constant regardless of the number of retries.

Setting the RetryMaxCount

The RetryMaxCount can be adjusted using the following function:

udp.h

void SetSendRetryMaxCount(uint32_t count)

The RetryMaxCount will be set to the value specified by count.

Configuring Sequence Guarantee

a. When using the Diarkis Module, the behavior of RUDP can be controlled through the type argument in functions like SendBroadcast defined in DiarkisP2PBase.h. Specify a value of the enumerated type RudpType for the type argument.

DiarkisP2PBase.h

uint16_t SendBroadcast(const uint8_t* payload, size_t payloadSize, RudpType type)

p2p.h

enum RudpType : uint8_t
{
    UNRELIABLE_UNORDERED = 0, // No delivery guarantee, no sequence guarantee (UDP)
    RELIABLE_UNORDERED = 1,   // Delivery guarantee, no sequence guarantee
    RELIABLE_ORDERED = 2      // Delivery guarantee, sequence guarantee
};

b. When directly using the library, set the bFixedOrder flag to true in the P2P communication data sending function found below.

p2p.h

Diarkis::System::Result RSend(const uint8_t* message, size_t messageSize, bool bFixedOrder)

Important Notes on Configuration

• SetSendRetryInterval and SetSendRetryMaxCount configure the settings for RUDP communication with the server. For P2P communication, use SetSendRetryIntervalP2P and SetSendRetryMaxCountP2P.

• If the RetryInterval is set too low or RetryMaxCount is too high, the client may need to send a large number of packets, significantly increasing network processing load.