This project contains workers written in both C and C++ and use CMake as their build system. Your system needs to satisfy the C++ prerequisites. In practice, this just means having a fairly recent compiler that supports C++11 or later.

Build the project and start it with the default launch configuration:

spatial worker build --target windows
spatial local launch

(Replacing windows with macos on macOS, or linux on Linux).

This will launch SpatialOS locally with a single C++ "physics" worker that updates the position of a single entity. You may also see a 2nd entity called "physics-worker" created. This entity represents the managed worker itself.

Note: If you run spatial worker build without a --target parameter (or with the wrong target parameter), then the CMake cache for each worker (workers/<worker>/cmake_build) may end up in a corrupt state. To recover, just run spatial worker clean to delete the CMake caches.

Now, you can connect either one of the two C client workers (one implemented using "direct" serialization, the other implemented using "vtable" serialization). These workers can be launched with the following commands:

• Client (direct): spatial local worker launch client_direct local
• Client (vtable): spatial local worker launch client_vtable local

This project is used to showcase the C API and how it can be used to implement a simple client worker which visualizes the state of a single entity whose position is updated by a "physics" worker. As serialization in the C API can be implemented in two different ways, we provide two implementations of the same worker in workers/c_client_direct and workers/c_client_vtable. Either one of these can be used as a basis for further experimentation, and the client worker that's not being used can easily be deleted without breaking any other functionality.

When a client worker connects, it sends a command to the C++ worker (on the sample.Login component). The C++ worker then modifies the entity's write ACLs to delegate component 1001 (sample.ClientData) to the client, using the CallerWorkerAttributes field of the CommandRequestOp. This causes the entity to be checked out by the client worker, and the client worker will begin to receive component updates for position changes. The physics worker will also begin to send a simple command to the client every few seconds.

The snapshot exists in both json and binary format in the snapshots folder. There is no script to generate the snapshot as the snapshot was written by hand in the json format, but it's possible to make simple changes to the json format and regenerate the binary snapshot from it. To update the binary snapshot after making a change, run the following command:

spatial project history snapshot convert --input-format=text --input=snapshots/default.json --output-format=binary --output=snapshots/default.snapshot