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Open source relay for UNET. Works with the HLAPI, MLAPI and all other UNET projects.
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MLAPI.Relay Bug fixes and client transport rewrite Aug 8, 2019
.gitignore Initial commit (Open source publish) Aug 7, 2018
LICENCE Rewrote most of the relays internal Aug 7, 2019
MLAPI.Relay.sln Rewrote most of the relays internal Aug 7, 2019 Update Aug 7, 2018

Please note that the MLAPI.Relay was an experimental implementation of a relay. This was written in the span of a few days. Might not be stable (probably is), but should be fairly performant. It has no fancy features to support client meshing, and direct connections for peer to peer


The documentation and the relay itself is currently WIP. This is subject to change.

The MLAPI.Relay is a relay designed for the UNET Transport to relay traffic between peers that are hidden behind a NAT. Relaying traffic can be expensive but will allow communication between peers, regardless of the host's NAT configuration. The MLAPI.Relay works just like the NetworkTransport. Despite the naming, the MLAPI.Relay does not have to be used in conjunction with the MLAPI library, but rather with any game built on the NetworkTransport (including the HLAPI). The MLAPI.Relay includes default configurations for use with the MLAPI, HLAPI as well as an empty template for custom setups. To use the relay, simply replace "NetworkTransport" with "RelayTransport" where the following NetworkTransport methods are used:

  • Connect
  • ConnectEndPoint
  • ConnectWithSimulator
  • AddHost
  • AddHostWithSimulator
  • AddWebsocketHost
  • Disconnect
  • Send
  • QueueMessageForSending
  • SendQueuedMessages
  • Receive
  • ReceiveFromHost


  • Written in .NET Core for Cross platform
  • Allows you to limit bandwidth (optional)


Unlike Unity's relay, the MLAPI.Relay does not require you to use any specific matchmaker. The MLAPI.Relay will pass the destination address when connecting rather than a relay-specific roomId. This allows you to run the MLAPI.Relay with any matchmaker (or without a matchmaker all together).

Setup requirements

The MLAPI.Relay requires there be at least one reliable channel type (regardless of what subtype of reliable channel that is).


The relay has a configuration file called config.json which consists of the three following parts:


This is the NetworkTransport connectionConfig. These options have to match up with your game's connectionConfig.


This is the NetworkTransport GlobalConfig. This tells the NetworkTransport how it should work.


Relay config contains many different fields:

  • maxConnections is the maximum amount of connections the relay can support.
  • port is the the port on which the relay will operate
  • bufferSize is the size of the buffer that will be allocated for messages (both inbound and outbound)
  • channels is the list of channelTypes that should be used (in the order they are added). Note that some high level libraries have default channels that are added in addition to the user channels. Due to this tendency, the relay has templates for the default channel configurations of both the MLAPI and the HLAPI. When using these templates, the channels added are only the library channels; additional user channels must be added manually. NOTE: mismatched channel configurations will result in errors and will prevent clients and/or hosts from connecting to the relay!
  • bandwidthGracePeriodLength is the length of the bandwidth grace period from the point when a client connects.
  • gracePeriodBandwidthLimit is the amount of bytes per second that is allowed during the bandwidth grace period for each client. If this 0 or less, the traffic will not be limited during the grace period.
  • bandwidthLimit is the amount of bytes per second that is allowed for each client after their respective the grace periods. If this is 0 or less, no limit will be set.
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