MLAPI Relay by MidLevel - 4


This is the repository for the MLAPI.Relay, a UNET Relay. This is where documentation and issues can be found and reported

Unknown VersionOtherUpdated 3 years agoCreated on May 27th, 2018
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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)
  • Update checking (optional). This will check for updates and inform you of new updates.
  • Deploy-and-forget Auto-update (optional). The auto update feature allows you to deploy the relay and it will auto update whenever needed. (NOT YET IMPLEMENTED)
  • Disable home calling. The MLAPI will only do connections to external sources for update checking purposes. This can be disabled.
  • Non external license checking. Even if, our servers were to go down (or in the unlikely event that we would shut down this service), your license would continue to work.


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)
  • updateChecking toggles wheter or not the relay should do web requests to check for updates. NOTE: this will not enable auto-update! If auto-update is disabled and this is enabled it will simply notify you if there is a newer version available.
  • autoUpdate toggles whether or not the relay will automatically download and deploy the latest release of the MLAPI.Relay (if there is a newer version than the currently used one). This requires updateChecking to be turned on.
  • licenceKey is the license key you got when purchasing your license. If this is empty or invalid, a trial license will be used.
  • 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.

Trial license

The trial license has no limitations except that only 20 concurrent connections are allowed. This is to allow for endless evaluation and development.

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