此页面由 Cloud Translation API 翻译。

连接组件

协议句柄是一个众所周知的对象，它提供了可使用组件命名空间发现的 FIDL 协议实现。功能路由描述了哪个组件应该充当任何给定客户端的提供程序。

请参考以下示例，了解 fuchsia.example.Foo 协议：

展示连接组件如何同时兼顾功能路由和协议传送的示意图。组件必须实现它们向其他组件提供的协议。

下图突出显示了执行连接所涉及的主要元素：

提供程序组件在清单的 capabilities 部分中静态声明协议。这样，组件框架就能够执行功能路由。
客户端组件在清单的 use 部分中静态请求协议。如果功能路由成功，此操作会在客户端的命名空间中创建 /svc/fuchsia.example.Foo 协议条目。
提供方代码在运行时发布实现。这会在提供程序的传出目录中的 /svc/fuchsia.example.Foo 中创建一个协议条目。
客户端代码在运行时连接到协议句柄。这会打开与提供程序组件中运行的实现的 FIDL 连接。

发布协议实现

实现 FIDL 协议的组件会在其组件清单中声明该协议并将其作为功能进行声明和公开。这样，组件框架就可以执行从该组件到拓扑中请求该功能的其他组件的功能路由。

{
    // ...
    capabilities: [
        { protocol: "fuchsia.example.Foo" },
    ],
    expose: [
        {
            protocol: "fuchsia.example.Foo",
            from: "self",
        },
    ],
}

功能路由会描述对协议的访问权限，但不会为连接建立必要的端点。组件必须使用 fuchsia.io 协议将实现发布为传出目录中的 /svc/ 句柄。生成的 FIDL 绑定会封装此句柄，并使提供程序能够连接请求句柄以开始接收 FIDL 消息。

Rust

let mut service_fs = ServiceFs::new_local();

// Serve the protocol
service_fs.dir("svc").add_fidl_service(PROTOCOL_NAME);
service_fs.take_and_serve_directory_handle().context("failed to serve outgoing namespace")?;

C++

// Serve the protocol
FooImplementation instance;
fidl::Binding<fuchsia::example::Foo> binding(&instance);
instance.event_sender_ = &binding.events();
fidl::InterfaceRequestHandler<fuchsia::example::Foo> handler =
    [&](fidl::InterfaceRequest<fuchsia::example::Foo> request) {
      binding.Bind(std::move(request));
    };
context->outgoing()->AddPublicService(std::move(handler));

连接到协议实现

客户端组件会在其组件清单中将协议声明为必需功能。这样，组件框架就可以确定组件是否有权访问协议实现。如果存在有效路由，则组件的命名空间会包含相应的 /svc/ 句柄。

{
    // ...
    use: [
        { protocol: "fuchsia.example.Foo" },
    ],
}

客户端组件使用 fuchsia.io 协议与协议实现建立连接并打开一个通道。生成的 FIDL 绑定会封装此通道，并使客户端能够开始向提供程序发送消息。

Rust

// Connect to FIDL protocol
let protocol = connect_to_protocol::<FooMarker>().expect("error connecting to echo");

C++

// Connect to FIDL protocol
fuchsia::example::FooSyncPtr proxy;
auto context = sys::ComponentContext::Create();
context->svc()->Connect(proxy.NewRequest());

练习：Echo 服务器和客户端

在本部分中，您将使用为 fidl.examples.routing.echo 生成的 FIDL 绑定在 Rust 中实现客户端和服务器组件。

启动模拟器

如果您尚未运行实例，请启动模拟器：

启动一个新的模拟器实例：

ffx emu start --headless

启动完成后，模拟器会输出以下消息并返回：

Logging to "$HOME/.local/share/Fuchsia/ffx/emu/instances/fuchsia-emulator/emulator.log"
Waiting for Fuchsia to start (up to 60 seconds)........
Emulator is ready.

启动软件包服务器，以使模拟器能够加载软件包：
```
fx serve
```

创建服务器组件

首先，创建一个新的组件项目以实现 echo 服务器。此组件将提供 Echo 协议并处理传入请求。

在 //vendor/fuchsia-codelab 目录中为名为 echo-server 的新组件创建项目基架：

mkdir -p vendor/fuchsia-codelab/echo-server

Rust

//vendor/fuchsia-codelab/echo-server
                        |- BUILD.gn
                        |- meta
                        |   |- echo.cml
                        |
                        |- src
                            |- main.rs

C++

//vendor/fuchsia-codelab/echo-server
                        |- BUILD.gn
                        |- meta
                        |   |- echo.cml
                        |
                        |- main.cc

将以下构建规则添加到 BUILD.gn 文件中，以构建并打包服务器组件：

Rust

echo-server/BUILD.gn:

import("//build/components.gni")
import("//build/rust/rustc_binary.gni")


rustc_binary("bin") {
  output_name = "echo-server"
  edition = "2021"

  deps = [
    "//vendor/fuchsia-codelab/echo-fidl:echo_rust",
    "//src/lib/diagnostics/inspect/runtime/rust",
    "//src/lib/diagnostics/inspect/rust",
    "//src/lib/fuchsia",
    "//src/lib/fuchsia-component",
    "//third_party/rust_crates:anyhow",
    "//third_party/rust_crates:futures",
  ]

  sources = [ "src/main.rs" ]
}

# Unpackaged component "#meta/echo_server.cm"
fuchsia_component("echo_server_cmp") {
  component_name = "echo_server"
  manifest = "meta/echo_server.cml"
  deps = [ ":bin" ]
}

fuchsia_package("echo-server") {
  package_name = "echo-server"
  deps = [ ":component" ]
}

C++

echo-server/BUILD.gn:

import("//build/components.gni")


executable("bin") {
  output_name = "echo-server"
  sources = [ "main.cc" ]

  deps = [
    "//vendor/fuchsia-codelab/echo-fidl:echo_hlcpp",
    "//sdk/lib/inspect/component/cpp",
    "//sdk/lib/sys/cpp",
    "//zircon/system/ulib/async-loop:async-loop-cpp",
    "//zircon/system/ulib/async-loop:async-loop-default",
  ]
}

# Unpackaged component "#meta/echo_server.cm"
fuchsia_component("echo_server_cmp") {
  component_name = "echo_server"
  manifest = "meta/echo_server.cml"
  deps = [ ":bin" ]
}

fuchsia_package("echo-server") {
  package_name = "echo-server"
  deps = [ ":component" ]
}

将 Echo 协议声明为服务器组件提供的功能，并将其公开以供父领域使用：

Rust

echo-server/meta/echo_server.cml:

{
    include: [
        "inspect/client.shard.cml",
        "syslog/client.shard.cml",
    ],

    // Information about the program to run.
    program: {
        // Use the built-in ELF runner.
        runner: "elf",

        // The binary to run for this component.
        binary: "bin/echo-server",
    },

    // Capabilities provided by this component.
    capabilities: [
        { protocol: "fidl.examples.routing.echo.Echo" },
    ],
    expose: [
        {
            protocol: "fidl.examples.routing.echo.Echo",
            from: "self",
        },
    ],
}

C++

echo-server/meta/echo_server.cml:

{
    include: [
        "inspect/client.shard.cml",
        "syslog/client.shard.cml",
    ],

    // Information about the program to run.
    program: {
        // Use the built-in ELF runner.
        runner: "elf",

        // The binary to run for this component.
        binary: "bin/echo-server",
    },

    // Capabilities provided by this component.
    capabilities: [
        { protocol: "fidl.examples.routing.echo.Echo" },
    ],
    expose: [
        {
            protocol: "fidl.examples.routing.echo.Echo",
            from: "self",
        },
    ],
}

实现服务器

打开主源文件，并将 import 语句替换为以下代码：

Rust

echo-server/src/main.rs:

use anyhow::Context;
use fidl_fidl_examples_routing_echo::{EchoRequest, EchoRequestStream};
use fuchsia_component::server::ServiceFs;
use fuchsia_inspect::{component, health::Reporter};
use futures::prelude::*;

Rust 的 FIDL 绑定会生成以 FIDL library 命名的 Rust 库 crate。对于 fidl.examples.routing.echo 库，生成的 crate 名称为 fidl_fidl_examples_routing_echo。如需了解详情，请参阅 Rust 绑定。

C++

echo-server/main.cc:

#include <fidl/examples/routing/echo/cpp/fidl.h>
#include <lib/async-loop/cpp/loop.h>
#include <lib/async-loop/default.h>
#include <lib/fidl/cpp/binding.h>
#include <lib/inspect/component/cpp/component.h>
#include <lib/sys/cpp/component_context.h>

将以下代码添加到 main() 以提供 Echo 协议：

Rust

echo-server/src/main.rs:

// Wrap protocol requests being served.
enum IncomingRequest {
    Echo(EchoRequestStream),
}

#[fuchsia::main(logging = false)]
async fn main() -> Result<(), anyhow::Error> {
    let mut service_fs = ServiceFs::new_local();

    // Initialize inspect
    component::health().set_starting_up();
    let _inspect_server_task = inspect_runtime::publish(
        component::inspector(),
        inspect_runtime::PublishOptions::default(),
    );

    // Serve the Echo protocol
    service_fs.dir("svc").add_fidl_service(IncomingRequest::Echo);
    service_fs.take_and_serve_directory_handle().context("failed to serve outgoing namespace")?;

    // Component is serving and ready to handle incoming requests
    component::health().set_ok();

    // Attach request handler for incoming requests
    service_fs
        .for_each_concurrent(None, |request: IncomingRequest| async move {
            match request {
                IncomingRequest::Echo(stream) => handle_echo_request(stream).await,
            }
        })
        .await;

    Ok(())
}

此代码执行以下步骤以提供 Echo 协议：

初始化 ServiceFs，并在传出目录中的 /svc/fidl.examples.routing.echo.Echo 下添加一个条目。
提供目录并开始监听传入连接。
将 handle_echo_request() 函数附加为任何匹配的 Echo 请求的请求处理程序。

C++

echo-server/main.cc:

int main(int argc, const char** argv) {
  async::Loop loop(&kAsyncLoopConfigAttachToCurrentThread);
  auto context = sys::ComponentContext::CreateAndServeOutgoingDirectory();

  // Initialize inspect
  inspect::ComponentInspector inspector(loop.dispatcher(), inspect::PublishOptions{});
  inspector.Health().StartingUp();

  // Serve the Echo protocol
  EchoImplementation echo_instance;
  fidl::Binding<fidl::examples::routing::echo::Echo> binding(&echo_instance);
  echo_instance.event_sender_ = &binding.events();
  fidl::InterfaceRequestHandler<fidl::examples::routing::echo::Echo> handler =
      [&](fidl::InterfaceRequest<fidl::examples::routing::echo::Echo> request) {
        binding.Bind(std::move(request));
      };
  context->outgoing()->AddPublicService(std::move(handler));

  // Component is serving and ready to handle incoming requests
  inspector.Health().Ok();

  return loop.Run();
}

此代码执行以下步骤以提供 Echo 协议：

初始化 ComponentContext，并在传出目录中的 /svc/fidl.examples.routing.echo.Echo 下添加一个条目。
提供目录并开始监听传入连接。
将 EchoImplementation 实例附加为任何匹配的 Echo 请求的请求处理程序。

添加以下代码以实现协议请求处理程序：

Rust

echo-server/src/main.rs:

// Handler for incoming service requests
async fn handle_echo_request(mut stream: EchoRequestStream) {
    while let Some(event) = stream.try_next().await.expect("failed to serve echo service") {
        let EchoRequest::EchoString { value, responder } = event;
        responder.send(value.as_ref().map(|s| &**s)).expect("failed to send echo response");
    }
}

EchoRequestStream 中的每个请求都由方法名称 (EchoString) 输入，并包含用于发回返回值的响应程序接口。

C++

echo-server/main.cc:

// Handler for incoming service requests
class EchoImplementation : public fidl::examples::routing::echo::Echo {
 public:
  void EchoString(fidl::StringPtr value, EchoStringCallback callback) override { callback(value); }
  fidl::examples::routing::echo::Echo_EventSender* event_sender_;
};

每个 Echo 协议方法都有对应的替换函数 (EchoString())，并包含用于发回返回值的回调接口。

此实现只会在响应载荷中“回显”请求中的字符串值。

创建客户端组件

创建另一个新的组件项目以实现 echo 客户端。此组件将连接到协议实现并发送请求。

在 //vendor/fuchsia-codelab 目录中为名为 echo-client 的新组件创建项目基架：

mkdir -p vendor/fuchsia-codelab/echo-client

Rust

//vendor/fuchsia-codelab/echo-client
                        |- BUILD.gn
                        |- meta
                        |   |- echo.cml
                        |
                        |- src
                            |- main.rs

C++

//vendor/fuchsia-codelab/echo-client
                        |- BUILD.gn
                        |- meta
                        |   |- echo.cml
                        |
                        |- main.cc

将以下构建规则添加到 BUILD.gn 文件中，以构建并打包客户端组件：

Rust

echo-client/BUILD.gn:

import("//build/components.gni")
import("//build/rust/rustc_binary.gni")


rustc_binary("bin") {
  output_name = "echo-client"
  edition = "2021"
  deps = [
    "//vendor/fuchsia-codelab/echo-fidl:echo_rust",
    "//src/lib/fuchsia",
    "//src/lib/fuchsia-component",
    "//third_party/rust_crates:anyhow",
    "//third_party/rust_crates:tracing",
  ]

  sources = [ "src/main.rs" ]
}

# Unpackaged component "#meta/echo_client.cm"
fuchsia_component("echo_client_cmp") {
  component_name = "echo_client"
  manifest = "meta/echo_client.cml"
  deps = [ ":bin" ]
}

fuchsia_package("echo-client") {
  package_name = "echo-client"
  deps = [ ":component" ]
}

C++

echo-client/BUILD.gn:

import("//build/components.gni")


executable("bin") {
  output_name = "echo-client"
  sources = [ "main.cc" ]

  deps = [
    "//vendor/fuchsia-codelab/echo-fidl:echo_hlcpp",
    "//sdk/lib/sys/cpp",
    "//sdk/lib/syslog/cpp",
    "//zircon/system/ulib/async-loop:async-loop-cpp",
    "//zircon/system/ulib/async-loop:async-loop-default",
  ]
}

# Unpackaged component "#meta/echo_client.cm"
fuchsia_component("echo_client_cmp") {
  component_name = "echo_client"
  manifest = "meta/echo_client.cml"
  deps = [ ":bin" ]
}

fuchsia_package("echo-client") {
  package_name = "echo-client"
  deps = [ ":component" ]
}

配置客户端的组件清单，以请求服务器公开的 fidl.examples.routing.echo.Echo 功能：

Rust

echo-client/meta/echo_client.cml:

{
    include: [
        // Enable logging on stdout
        "syslog/client.shard.cml",
    ],

    // Information about the program to run.
    program: {
        // Use the built-in ELF runner.
        runner: "elf",

        // The binary to run for this component.
        binary: "bin/echo-client",

        // Program arguments
        args: [ "Hello Fuchsia!" ],
    },


    // Capabilities used by this component.
    use: [
        { protocol: "fidl.examples.routing.echo.Echo" },
    ],
}

C++

echo-client/meta/echo_client.cml:

{
    include: [
        // Enable logging.
        "syslog/client.shard.cml",
    ],

    // Information about the program to run.
    program: {
        // Use the built-in ELF runner.
        runner: "elf",

        // The binary to run for this component.
        binary: "bin/echo-client",

        // Program arguments
        args: [ "Hello Fuchsia!" ],
    },


    // Capabilities used by this component.
    use: [
        { protocol: "fidl.examples.routing.echo.Echo" },
    ],
}

实现客户端

与 echo-args 类似，客户端会将程序参数作为消息传递给服务器。将以下程序参数添加到 echo_client.cml：

Rust

echo-client/meta/echo_client.cml:

// Information about the program to run.
program: {
    // Use the built-in ELF runner.
    runner: "elf",

    // The binary to run for this component.
    binary: "bin/echo-client",

    // Program arguments
    args: [ "Hello Fuchsia!" ],
},

C++

echo-client/meta/echo_client.cml:

// Information about the program to run.
program: {
    // Use the built-in ELF runner.
    runner: "elf",

    // The binary to run for this component.
    binary: "bin/echo-client",

    // Program arguments
    args: [ "Hello Fuchsia!" ],
},

打开主源文件，并将 import 语句替换为以下代码：

Rust

echo-client/src/main.rs:

use fidl_fidl_examples_routing_echo::EchoMarker;
use fuchsia_component::client::connect_to_protocol;

C++

echo-client/main.cc:

#include <fidl/examples/routing/echo/cpp/fidl.h>
#include <lib/fidl/cpp/string.h>
#include <lib/sys/cpp/component_context.h>
#include <lib/syslog/cpp/log_settings.h>
#include <lib/syslog/cpp/macros.h>

#include <cstdlib>
#include <iostream>
#include <string>

将以下代码添加到 main() 以连接到 Echo 协议并发送请求：

Rust

echo-client/src/main.rs:

#[fuchsia::main]
async fn main() -> Result<(), anyhow::Error> {
    // Parse arguments, removing binary name
    let mut args: Vec<String> = std::env::args().collect();
    args.remove(0);

    // Connect to FIDL protocol
    let echo = connect_to_protocol::<EchoMarker>().expect("error connecting to echo");

    // Send messages over FIDL interface
    for message in args {
        let out = echo.echo_string(Some(&message)).await.expect("echo_string failed");
        tracing::info!("Server response: {}", out.as_ref().expect("echo_string got empty result"));
    }

    Ok(())
}

EchoMarker 提供了一个封装容器，用于按名称连接到公开的 capability，并返回打开的 EchoProxy 接口的句柄。此代理包含 echo_string() FIDL 协议方法。

C++

echo-client/main.cc:

int main(int argc, const char* argv[], char* envp[]) {
  // Set tags for logging.
  fuchsia_logging::SetTags({"echo_client"});

  // Connect to FIDL protocol
  fidl::examples::routing::echo::EchoSyncPtr echo_proxy;
  auto context = sys::ComponentContext::Create();
  context->svc()->Connect(echo_proxy.NewRequest());

  // Send messages over FIDL interface for each argument
  fidl::StringPtr response = nullptr;
  for (int i = 1; i < argc; i++) {
    ZX_ASSERT(echo_proxy->EchoString(argv[i], &response) == ZX_OK);
    if (!response.has_value()) {
      FX_SLOG(INFO, "echo_string got empty result");
    } else {
      FX_SLOG(INFO, "Server response", FX_KV("response", response->c_str()));
    }
  }

  return 0;
}

EchoSyncPtr 提供了一个封装容器，用于按名称连接到公开的 capability，并返回打开的代理接口的句柄。此代理包含 EchoString() FIDL 协议方法。

集成组件

服务器提供的功能必须通过组件框架路由到客户端。要实现这一点，您需要实现一个领域组件来充当父级并管理功能路由。

为领域产品定义创建新的项目目录：

mkdir -p vendor/fuchsia-codelab/echo-realm

//vendor/fuchsia-codelab/echo-realm
                        |- BUILD.gn
                        |- meta
                        |   |- echo_realm.cml

创建包含以下内容的新组件清单文件 meta/echo_realm.cml：

echo-realm/meta/echo_realm.cml:

{
    // Two children: a server and client.
    children: [
        {
            name: "echo_server",
            url: "#meta/echo_server.cm",
        },
        {
            name: "echo_client",
            url: "#meta/echo_client.cm",
        },
    ],
    offer: [
        // Route Echo protocol from server to client.
        {
            protocol: "fidl.examples.routing.echo.Echo",
            from: "#echo_server",
            to: "#echo_client",
        },

        // Route diagnostics protocols to both children.
        {
            protocol: [
                "fuchsia.inspect.InspectSink",
                "fuchsia.logger.LogSink",
            ],
            from: "parent",
            to: [
                "#echo_client",
                "#echo_server",
            ],
        },
    ],
}

这会创建一个组件领域，其中服务器和客户端作为子组件，并将 fidl.examples.routing.echo.Echo 协议功能路由到客户端。

添加 BUILD.gn 文件，以便为 Realm 组件创建构建目标：

echo-realm/BUILD.gn:

import("//build/components.gni")

fuchsia_component("echo_realm") {
  manifest = "meta/echo_realm.cml"
}

fuchsia_package("echo-realm") {
  deps = [
    ":echo_realm",
    "//vendor/fuchsia-codelab/echo-server:component",
    "//vendor/fuchsia-codelab/echo-client:component",
  ]
}

更新 build 配置以包含新组件：

fx set workstation_eng.x64 \
    --with //vendor/fuchsia-codelab/echo-server \
    --with //vendor/fuchsia-codelab/echo-client \
    --with //vendor/fuchsia-codelab/echo-realm

再次运行 fx build 以构建组件：

fx build

将组件添加到拓扑中

您要将组件添加到 ffx-laboratory（一个用于产品的核心领域内开发的受限集合）。通过集合，可以在运行时动态创建和销毁组件。

将 echo-realm 组件网址和 ffx-laboratory 内的相应名称传递给 ffx component create，以创建组件实例：

ffx component create /core/ffx-laboratory:echo-realm \
    fuchsia-pkg://fuchsia.com/echo-realm#meta/echo_realm.cm

然后，使用 ffx component resolve 解析 echo-realm 组件：

ffx component resolve /core/ffx-laboratory:echo-realm

使用 ffx component show 验证服务器和客户端的实例是否也同时创建为子组件：

ffx component show echo

               Moniker: /core/ffx-laboratory:echo-realm/echo_client
                   URL: #meta/echo_client.cm
                  Type: CML static component
       Component State: Unresolved
       Execution State: Stopped

               Moniker: /core/ffx-laboratory:echo-realm/echo_server
                   URL: #meta/echo_server.cm
                  Type: CML static component
       Component State: Unresolved
       Execution State: Stopped

               Moniker: /core/ffx-laboratory:echo-realm
                   URL: fuchsia-pkg://fuchsia.com/echo-realm#meta/echo_realm.cm
                  Type: CML dynamic component
       Component State: Resolved
       Execution State: Stopped
           Merkle root: 666c40477785f89b0ace22b30d65f1338f1d308ecceacb0f65f5140baa889e1b

验证组件交互

使用 ffx component start 启动现有的客户端组件实例：

ffx component start /core/ffx-laboratory:echo-realm/echo_client

打开另一个终端窗口，并验证客户端组件的日志输出：

ffx log --filter echo

您应该会在设备日志中看到以下输出：

[echo_client][I] Server response: Hello, Fuchsia!

在客户端连接到 fidl.examples.routing.echo.Echo capability 后，服务器组件便会启动，并会继续运行以处理其他 FIDL 请求。

使用 ffx component show 查看在组件实例树中运行的 echo 服务器：

ffx component show echo_server

               Moniker: /core/ffx-laboratory:echo-realm/echo_server
                   URL: #meta/echo_server.cm
                  Type: CML static component
       Component State: Resolved
 Incoming Capabilities: fuchsia.logger.LogSink
  Exposed Capabilities: diagnostics
                        fidl.examples.routing.echo.Echo
       Execution State: Running
                Job ID: 474691
            Process ID: 474712
           Running for: 2026280474361 ticks
           Merkle root: 666c40477785f89b0ace22b30d65f1338f1d308ecceacb0f65f5140baa889e1b
 Outgoing Capabilities: diagnostics
                        fidl.examples.routing.echo.Echo

销毁实例

使用以下命令清理 echo-realm 实例：

ffx component destroy /core/ffx-laboratory:echo-realm

Fuchsia 接口定义语言

集成测试