DCS gRPC Server

DCS gRPC is an RPC (Remote Procedure Call) server that allows network clients to interact with a currently running mission on a DCS server.

Installation

Download

Download the latest version of the server from the Releases and extract the zip file into your DCS Server directory.

This is typically found in C:\Users\USERNAME\Saved Games\DCS.openbeta_server. Once extracted you will have a Scripts\DCS-gRPC folder, a Mods\Tech\DCS-gRPC folder, and a Scripts\Hooks\DCS-gRPC.lua file in your server folder. As well as these scripts there will be a Docs/DCS-gRPC folder containing documentation and a Tools/DCS-gRPC folder containing client tools.

Prepare DCS

To make the gRPC server available in the mission scripting environment, add the following line to your MissionScripting.lua file that is found by default in the DCS World install folder at C:\Program Files\Eagle Dynamics\DCS World\Scripts\MissionScripting.lua. If you installed the server in another location then look for the Scripts\MissionScripting.lua file in there.

Note: The following file is in diff format to highlight the line that has been added. Do note include the + symbol when you paste into the MissionScripting.lua file.

  --Initialization script for the Mission lua Environment (SSE)

  dofile('Scripts/ScriptingSystem.lua')
+ dofile(lfs.writedir()..[[Scripts\DCS-gRPC\grpc-mission.lua]])

  --Sanitize Mission Scripting environment
  --This makes unavailable some unsecure functions.
  --Mission downloaded from server to client may contain potentialy harmful lua code that may use these functions.
  --You can remove the code below and make availble these functions at your own risk.

  local function sanitizeModule(name)
    _G[name] = nil
    package.loaded[name] = nil
  end

  do
    sanitizeModule('os')
    sanitizeModule('io')
    sanitizeModule('lfs')
    _G['require'] = nil
    _G['loadlib'] = nil
    _G['package'] = nil
  end

Running DCS-gRPC

There are two ways of running DCS-gRPC. One way allows it to run regardless of what mission is running and the other means that DCS-gRPC will only run if the mission scripting itself enables it.

Running regardless of mission

Create the file Saved Games\DCS\Config\dcs-grpc.lua and add the line below

autostart = true

As well as this you can set other options in this file. All options and the config file itself are optional – you only have to create the config file and set an option if you want to change any of the default values (the list below shows the default values). The available options are:

-- Whether the `Eval` method is enabled or not.
evalEnabled = false

-- The host the gRPC listens on (use "0.0.0.0" to listen on all IP addresses of the host).
host = "127.0.0.1"

-- The port to listen on.
port = 50051

-- Whether debug logging is enabled or not.
debug = false

-- Limit of calls per second that are executed inside of the mission scripting environment.
throughputLimit = 600

-- Whether the integrity check, meant to spot installation issues, is disabled.
integrityCheckDisabled = false

-- Whether or not authentication is required
auth.enabled = false 
-- Authentication tokens table with client names and their tokens for split tokens. 
auth.tokens = {
  -- client => clientName, token => Any token. Advice to use UTF-8 only. Length not limited explicitly 
  { client = "SomeClient", token = "SomeToken" }, 
  { client = "SomeClient2", token = "SomeOtherToken" }
}

-- The default TTS provider to use if a TTS request does not explicitly specify another one.
tts.defaultProvider = "win"

-- Your Azure access key.
tts.provider.azure.key = "..."

-- The Azure region to use (see https://learn.microsoft.com/en-us/azure/cognitive-services/speech-service/regions).
tts.provider.azure.region = "westeurope"

-- The default Azure voice to use (see https://learn.microsoft.com/azure/cognitive-services/speech-service/language-support).
tts.provider.azure.defaultVoice = "en-US-AriaNeural"

-- Your AWS key.
tts.provider.aws.key = "..."

-- Your AWS secret key.
tts.provider.aws.secret = "..."

-- Your AWS region (see https://docs.aws.amazon.com/general/latest/gr/pol.html).
tts.provider.aws.region = "eu-central-1"

-- The default AWS voice to use (see https://docs.aws.amazon.com/polly/latest/dg/voicelist.html).
tts.provider.aws.defaultVoice = "Brian"

-- Your Google Cloud access key.
tts.provider.gcloud.key = "..."

-- The default Google Cloud voice to use (see https://cloud.google.com/text-to-speech/docs/voices).
tts.provider.gcloud.defaultVoice = "en-GB-Neural2-A"

-- The default Windows voice to use (see https://support.microsoft.com/en-us/windows/appendix-a-supported-languages-and-voices-4486e345-7730-53da-fcfe-55cc64300f01).
-- Requires at least Windows Server 2019 to work properly.
tts.provider.win.defaultVoice = "David"

-- Your SRS server's address.
srs.addr = "127.0.0.1:5002"

Once you have done this start the DCS server and skip to the "Confirming that DCS-gRPC is running" section of this README.

Running only if the mission scripting enables it

Make sure that the file Saved Games\DCS\Config\dcs-grpc.lua does not exist (Delete if it does).

Add the following code to your mission. This will start the DCS-gRPC server. You can add this code to a DO SCRIPT trigger in your .miz file or you can add this code to an existing lua file that your mission may be running.

-- Load the gRPC server into the mission
GRPC.load()

As well as this you can set other options in the script before GRPC.Load() . These are listed below:

-- Whether the `Eval` method is enabled or not.
GRPC.evalEnabled = false

-- The host the gRPC listens on (use "0.0.0.0" to listen on all IP addresses of the host).
GRPC.host = '127.0.0.1'

-- The port to listen on.
GRPC.port = 50051

-- Whether debug logging is enabled or not.
GRPC.debug = false

-- Limit of calls per second that are executed inside of the mission scripting environment.
GRPC.throughputLimit = 600

For example:

GRPC.host = '0.0.0.0'
GRPC.load()

Confirming that DCS-gRPC is running

To confirm that the server is running check the \Logs\dcs.log file and look for entries prefixed with GRPC. You can also check for the present of a \Logs\grpc.log file.

The server will be running on port 50051 by default.

Lua API

DCS-gRPC provides the following Lua APIs to interact with the server from within Lua.

• GRPC.tts(ssml, frequency[, options]) - Synthesize text (ssml; SSML tags supported) to speech and transmit it over SRS on the frequency with the following optional options (and their defaults):

  {
      -- The plain text without any transformations made to it for the purpose of getting it spoken out
      -- as desired (no SSML tags, no FOUR NINER instead of 49, ...). Even though this field is
      -- optional, please consider providing it as it can be used to display the spoken text to players
      -- with hearing impairments.
      plaintext = null, -- e.g. `= "Hello Pilot"`
  
      -- Name of the SRS client.
      srsClientName = "DCS-gRPC",
  
      -- The origin of the transmission. Relevant if the SRS server has "Line of
      -- Sight" and/or "Distance Limit" enabled.
      position = {
          lat = 0.0,
          lon = 0.0,
          alt = 0.0, -- in meters
      },
  
      -- The coalition of the transmission. Relevant if the SRS server has "Secure
      -- Coalition Radios" enabled. Supported values are: `blue` and `red`. Defaults
      -- to being spectator if not specified.
      coalition = null,
  
      -- TTS provider to be use. Defaults to the one configured in your config or to Windows'
      -- built-in TTS. Examples:
      -- `= { aws = {} }` / `= { aws = { voice = "..." } }` enable AWS TTS
      -- `= { azure = {} }` / `= { azure = { voice = "..." } }` enable Azure TTS
      -- `= { gcloud = {} }` / `= { gcloud = { voice = "..." } }` enable Google Cloud TTS
      -- `= { win = {} }` / `= { win = { voice = "..." } }` enable Windows TTS
      provider = null,
  }

Client Development

DCS-gRPC, as the name implies, uses the gRPC framework to handle communication between clients and the server. gRPC supports a wide variety of languages which allows you to develop clients in the languages of your choice.

In order to develop clients for DCS-gRPC you must be familiar with gRPC concepts so we recommend reading the gRPC documentation for your language.

The gRPC .proto files are available in the Docs/DCS-gRPC folder and also available in the Github repo

Client Authentication

If authentication is enabled on the server you will have to add X-API-Key to the metadata/headers. Below are some example on what it could look like in your code.

Examples

dotnet / c#

You can either set the Metadata for each request or you can create a GrpcChannel with an interceptor that will set the key each time.

For a single request:

var client = new MissionService.MissionServiceClient(channel);

Metadata metadata = new Metadata()
{
    { "X-API-Key", "<yourKey>" }
};

var response = client.GetScenarioCurrentTime(new GetScenarioCurrentTimeRequest { }, headers: metadata, deadline: DateTime.UtcNow.AddSeconds(2));

For all requests on a channel:

public GrpcChannel CreateChannel(string host, string post, string? apiKey)
{
  GrpcChannelOptions options = new GrpcChannelOptions();
  if (apiKey != null)
  {
      CallCredentials credentials = CallCredentials.FromInterceptor(async (context, metadata) =>
      {
          metadata.Add("X-API-Key", apiKey);
      });

      options.Credentials = ChannelCredentials.Create(ChannelCredentials.Insecure, credentials) ;
  }

  return GrpcChannel.ForAddress($"http://{host}:{port}", options);
}

Server Development

The following section is only applicable to people who want to developer the DCS-gRPC server itself.

Build Dependencies

• Rust >=1.64
• rustfmt (rustup component add rustfmt)

Build

make build

You may need to use the following in powershell

cargo build

Or if you want to use the hot reloading DLL (this is the same as make build):

cargo build --features hot-reload
copy target/debug/dcs_grpc.dll target/debug/dcs_grpc_hot_reload.dll

Prepare DCS

For development:

• update your MissionScripting.lua to load grpc-mission.lua from your local clone, e.g.:

  - dofile(lfs.writedir()..[[Scripts\DCS-gRPC\grpc-mission.lua]])
  + dofile([[C:\Development\DCS-gRPC\rust-server\lua\DCS-gRPC\grpc-mission.lua]])

• add custom dllPath and luaPath settings to your Saved Games\DCS\Config\dcs-grpc.lua:

  dllPath = [[C:\Development\DCS-gRPC\rust-server\target\debug\]]
  luaPath = [[C:\Development\DCS-gRPC\rust-server\lua\DCS-gRPC\]]

• copy the hook script from lua\Hooks\DCS-gRPC.lua to Scripts\Hooks\DCS-gRPC.lua

• set integrityCheckDisabled = true in your Saved Games\DCS\Config\dcs-grpc.lua to allow changes to Lua without having to re-compile the dll

Debugging

• Search for [GRPC] in the DCS logs
• Consult the gRPC Server logs at Saved Games\DCS.openbeta\Logs\gRPC.log

Test the running server via grpcurl: (Remove the .exe when running on Linux).

Tip

FOR WINDOWS USERS on the command prompt, you may need to wrap the JSON in double quotes instead of single quotes in the commands below. Try this if you get "Too Many Arguments" error

grpcurl.exe -plaintext -import-path ./protos -proto ./protos/dcs/dcs.proto -d '{\"text\": \"Works!\", \"display_time\": 10, \"clear_view\": false}' 127.0.0.1:50051 dcs.trigger.v0.TriggerService/OutText

or watch the mission event stream via:

grpcurl.exe -plaintext -import-path ./protos -proto ./protos/dcs/dcs.proto -d '{}' 127.0.0.1:50051 dcs.mission.v0.MissionService/StreamEvents

REPL

DCS-gRPC provides the facility to directly run lua code inside the mission scripting environment. This feature is mainly intended for development and is disabled by default. You can enable it via the GRPC settings (See Settings section above)

To build and run the repl run the following commands

cargo build -p dcs-grpc-repl
# Make sure your DCS mission is running
cargo run -p dcs-grpc-repl

Note that the REPL is hardcoded to connect to localhost on the default port

Once connected you can enter lua code to execute. Prefix the lua with return to have the lua code return a value to the client. For example:

return Group.getByName('Aerial-1')
= {
    "id_": 1
}

return Group.getByName('Aerial-1'):getName()
= Aerial-1

The REPL is also available in the release and can be run by running Tools/DCS-gRPC/repl.exe

Contributions

This repository is powered by GitHub Actions for the Continuous Integration (CI) services. The same CI checks would be triggered and executed as you push code to your forked repository, and providing early feedback before a maintainer executes a manual execution on the pull request.

Troublshooting

Linker Error 1104

If you see LINK : fatal error LNK1104: cannot open file when running cargo build make sure that there is no running DCS mission as that locks the DLL files. Exit the mission (You do not have to exit DCS) then re-run the command before restarting the mission.