PlayFab Party and direct peer-to-peer connections

Artigo
11/10/2023

This page explains how you can enable and use direct peer-to-peer connections in PlayFab Party using example game code. It also includes considerations to help you evaluate when to use direct peer-to-peer connections in your games.

When to use direct peer-to-peer connections

PlayFab Party supports a wide variety of communication topologies. Conceptually, all chat or data messages are from one peer device or user directly to others. However, Party will automatically leverage a transparent cloud relay service to avoid common environmental and security problems with establishing direct peer-to-peer connections. You can achieve low latency data transmission by leveraging its background quality of service (QoS) measurements. (For more info, see PlayFab Party QoS measurements.) You can optionally enable direct peer-to-peer connections to reduce data transmission latency further. Due to security concerns detailed under "Security considerations" below, Microsoft recommends that you use our cloud relay service instead of enabling direct peer-to-peer connection unless your title has strict latency requirements.

Platform support

Direct peer connectivity is supported in the Windows 10, Microsoft Game Core, Nintendo Switch, PlayStation®4, and PlayStation®5 versions of the Party library. Other versions of the library will always use the cloud relay for data transmission, regardless of the direct peer connectivity options specified through the client API.

"PlayStation" is a registered trademark or trademark of Sony Interactive Entertainment Inc.

Security considerations

Because direct peer connectivity are used to send data directly between clients, the clients all need to know how to connect to one another. This is done by sharing client IP addresses between clients in a game session together. For example, if a 16 player multiplayer game uses direct peer connectivity to update player positions, each of the 16 game clients needs to know the IP addresses of the 15 other clients to know who to send data to.

Sharing IP addresses between game clients is a security risk. Sharing IP addresses may allow bad actors to detect the IP address and use it to maliciously attack other players outside of games. A common method to carry out these attacks if through Denial-of-Service (DOS) attacks, or a variation called Distributed Denial of Service (DDOS) attacks. The attacks work by attempting to overwhelm a network with superfluous network traffic. If an attacker can send enough network traffic to their victim, the victim’s network hardware (modem and router) has to spend all its time processing the superfluous traffic, and doesn't have any time to do its normal jobs of processing legitimate networking connections. Effectively, this means that the victim can’t use their network for the entire duration of the attack. This is frequently referred to as getting "booted offline."

In conclusion, successful direct peer connectivity may provide lower latency between some devices. However, attempting to establish it also requires users to disclose their IP addresses to others, which may enable malicious users to attack their devices and internet connections outside of the title. Direct peer connection also may not be permitted on certain platforms for policy reasons. Be sure to use the appropriate direct peer connectivity options for your performance and security goals. If you decide to use direct peer connectivity after weighing the risks, use the following examples to opt-in your title on a per-network and per-device basis.

LAN scenarios

Direct peer connectivity in Party can be used to enable extremely low latency in LAN scenarios. Even in these scenarios, however, limited Internet connectivity is required to support user authentication, LiveOps data and insights, and voice chat accessibility features.

Upstream bandwidth considerations

Using direct peer-to-peer connectivity may increase your game's upstream bandwidth usage. When transmitting a game or voice message through the cloud relay service, Party sends a single message to the service; the service then replicates and forwards the message to each target device. When transmitting a game or voice message through direct peer-to-peer connections, Party replicates and sends the message through a direct connection for each target device to which a direct peer-to-peer connection has been established. Therefore, your game's upstream bandwidth usage will scale proportionally with the number of devices to which a direct peer-to-peer connection has been established. Consider whether this increase in upstream bandwidth is acceptable for your game before enabling direct peer-to-peer connections.

How to use direct peer-to-peer connections in your game

Enabling direct peer-to-peer connections in your network

When creating a network via PartyManager::CreateNewNetwork(), you can specify various network configuration parameters through the PartyNetworkConfiguration provided to the call. You can use the PartyNetworkConfiguration::directPeerConnectivityOptions field to specify whether and how direct peer-to-peer connectivity is supported for devices in the network.

The following example shows a network configuration that specifies direct peer-to-peer connections should be attempted among all devices in the network, regardless of platform type or login provider.

PartyNetworkConfiguration configuration = {};
configuration.directPeerConnectivityOptions = PartyDirectPeerConnectivityOptions::AnyPlatformType | PartyDirectPeerConnectivityOptions::AnyEntityLoginProvider;
// Initialize the rest of the network configuration parameters appropriately for your game before using.

As part of successfully authenticating an initial user into a network, a device may attempt to establish direct peer-to-peer connections with other devices already participating in the network when permitted by the network configuration. For attempts that are successful, endpoint messages and chat data between the devices will be transmitted using those direct connections. For attempts that fail due to environmental incompatibilities between the devices, all communication between those devices will be transmitted via transparent cloud relay servers instead. If the devices aren't permitted to attempt direct peer connections by the network configuration, then they never exchange IP address information and will always transmit endpoint messages and chat data via transparent cloud relay servers.

Note

Establishing direct peer connectivity is best effort and may not be possible due to environmental factors, per-device connectivity options, or platform policy. For more information about evaluating whether a direct peer-to-peer connection was established to a particular device, see Evaluating the connection type and latency.

Constraining direct peer connectivity per device

Besides the direct peer connectivity options in the network configuration, direct peer connectivity may be further constrained by a device for all networks into which it authenticates by using PartyManager::SetOption() to set PartyOption::LocalDeviceDirectPeerConnectivityOptionsMask. All flags are evaluated using a bitwise AND operation. That is, a particular flag is only in effect for a given network's pair of devices if it's enabled in three places: the network configuration, and both devices' respective local mask options. Even if the network configuration permits direct peer connectivity of the relevant form, either device can independently opt out of the IP address disclosure and direct connection attempts between them by not enabling the flag in its local device mask option. In versions of the library that support direct peer connectivity, the PartyOption::LocalDeviceDirectPeerConnectivityOptionsMask value defaults to permitting all direct peer connections enabled by networks. Therefore, you only need to configure it if you have device-specific requirements to prevent some or all direct peer connectivity involving the local device.

The following example shows how to constrain direct peer connectivity for the local device so that it will only attempt to establish direct peer connectivity to devices of the same platform.

PartyDirectPeerConnectivityOptions localDeviceMask = PartyDirectPeerConnectivityOptions::SamePlatformType | PartyDirectPeerConnectivityOptions::AnyEntityLoginProvider;
PartyError error = PartyManager::GetSingleton().SetOption(nullptr, PartyOption::LocalDeviceDirectPeerConnectivityOptionsMask, &localDeviceMask);
if (PARTY_FAILED(error))
{
    printf("Failed to set local device direct peer connectivity options mask! error = 0x%08x\n", error);
}

Evaluating the connection type and latency

You can determine whether the local device established a direct peer-to-peer connection to a specific remote device by calling PartyNetwork::GetDeviceConnectionType().

We recommend that you don't actively enforce the availability of a direct peer-to-peer connection for any given pair of devices (i.e., don't call PartyNetwork::LeaveNetwork() if PartyNetwork::GetDeviceConnectionType() reports a value other than PartyDeviceConnectionType::DirectPeerConnection) since the specific underlying transmission method in use doesn't alter the overall logical ability to communicate. If your game design has stringent requirements for maximum message latency that encourage direct peer connectivity, it's better to take action on the current concrete observations of that latency as reported by the PartyEndpointStatistic::AverageDeviceRoundTripLatencyInMilliseconds statistic rather than make abstract assumptions based on transmission mechanism. Otherwise you might continually hinder users trying to play with the same set of friends who always need to use nearby transparent cloud relay servers due to environmental factors beyond their control.

The following example shows how to inspect the round trip latency from a localEndpoint to a remoteEndpoint in a network.

// A helper for inspecting the connection type and average round trip latency between a local endpoint and a remote
// endpoint in a network.
void PrintConnectionTypeAndLatency(
    PartyNetwork* network,
    PartyLocalEndpoint* localEndpoint,
    PartyEndpoint* remoteEndpoint
    )
{
    // Retrieve the device associated with the remote endpoint.
    PartyDevice* remoteDevice;
    PartyError error = remoteEndpoint->GetDevice(&remoteDevice);
    if (PARTY_FAILED(error))
    {
        printf("Failed to get the remote device! error = 0x%08x\n", error);
        return;
    }

    // Get the device connection type.
    PartyDeviceConnectionType connectionType;
    PartyError error = network->GetDeviceConnectionType(remoteDevice, &connectionType);
    if (PARTY_FAILED(error))
    {
        printf("Failed to get device connection type! error = 0x%08x\n", error);
        return;
    }

    // Retrieve the latency statistic.
    PartyEndpointStatistic latencyStatistic = PartyEndpointStatistic::AverageDeviceRoundTripLatencyInMilliseconds;
    uint64_t latencyStatisticValue;
    error = localEndpoint->GetEndpointStatistics(
        1,                       // targetEndpointCount
        &remoteEndpoint,         // targetEndpoints
        1,                       // statisticCount
        &latencyStatistic,       // statisticTypes
        &latencyStatisticValue); // statisticValues
    if (PARTY_FAILED(error))
    {
        printf("Failed to get latency statistic! error = 0x%08x\n", error);
        return;
    }

    // Print the results.
    printf("Local endpoint 0x%p and remote endpoint 0x%p in network 0x%p have average round trip latency %llu ms and device connection type %i\n",
        localEndpoint,
        remoteEndpoint,
        network,
        latencyStatisticValue,
        static_cast<int32_t>(connectionType));
}

Changes in connection type

It's possible that changing environmental conditions can disrupt a direct peer connection such that it becomes unusable for PlayFab Party. If this happens, the devices attempt to fall back to communicating via the cloud relay server. If relayed communication is still possible then the PartyNetwork::GetDeviceConnectionType() function will begin reporting PartyDeviceConnectionType::RelayServer and the devices will remain in the Party network using the new connection type going forward. Otherwise, the devices with disrupted connectivity will leave the network.

Warning

Chat and game messages that were still in the process of being transmitted or received on the direct peer connection when it was disrupted may never arrive, even if they were sent using PartySendMessageOptions::GuaranteedDelivery, and even if they are no longer counted in the PartyEndpointStatistic::CurrentlyQueuedSendMessages or PartyEndpointStatistic::CurrentlyActiveSendMessages values returned by PartyLocalEndpoint::GetEndpointStatistics(). Additionally, messages transmitted during the connection type transition period could arrive out of order even if sent using PartySendMessageOptions::SequentialDelivery. Your title should be prepared for this possibility of data loss and misordering when using direct peer connections and these PartySendMessageOptions.

A connection type of PartyDeviceConnectionType::RelayServer will never change to another type, regardless of whether that value was assigned when the device initially joined the network or after a previously disrupted direct peer connection.

Billing meters

The same billing meters are applied in networks that use direct peer-to-peer connections as in networks that use the cloud relay service. However, only game or voice data that goes through the cloud relay service count toward the Network egress and Party voice meters.

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