Services: list, call, response

[jhurliman]

No description provided.

[jhurliman]

An example implementation of calling ROS 2 services from a bridge can be found here: https://github.com/v-kiniv/rws/blob/main/src/client_handler.cpp#L406-L450. The method is straightforward, most of the work is in JSON<->CDR serde. We can avoid this by using our client binary serialization already used for topic publishing.

ROS 2 listing services: std::map<std::string, std::vector<std::string>> services = node_->get_service_names_and_types();

ROS 2 calling a service:

auto client = node_->create_generic_client(serviceName, serviceType, rmw_qos_profile_services_default, nullptr);
// if we include an immediate response back to clients calling a service, we can skip
// the wait_for_service() call and just return a failure if the service isn't available
while (!client->wait_for_service(1s)) { ... }
using ServiceResponseFuture = rws::GenericClient::SharedFuture;
auto callback = [&](ServiceResponseFuture future) {
  ConstSharedMessage msg = future.get();
  // send this message back to the client
};
client->async_send_request(msgFromClient, callback);
// send a confirmation to the client their service call was initiated?

[jhurliman]

Based on the ROS 2 notes above, I think the bridge protocol for services could roughly look like this:

• op: advertiseService // server -> client
• op: unadvertiseService // server -> client
• op: callService // client -> server
• op: serviceAcknowledgement // server -> client
• op: serviceResponse // server -> client

[achim-k]

• op: serviceAcknowledgement // server -> client

What is this for? Acknowledging a client's service call request?

[jhurliman]

Let's drop serviceAcknowledgement, but send an error back if the service is not running or there's another failure to initiate the service call.