本頁面由 Cloud Translation API 翻譯而成。

連結元件

通訊協定控制代碼為知名物件，提供實作 FIDL 通訊協定，可透過元件命名空間探索。功能轉送描述應做為任何特定用戶端的供應器。

請參考下列 fuchsia.example.Foo 通訊協定的範例：

這張圖表顯示連結元件如何結合能力轉送和通訊協定提供。元件必須支援其他元件提供的通訊協定實作。

下圖醒目顯示執行連線的主要元素：

供應商元件會以靜態方式宣告資訊清單 capabilities 區段中的通訊協定。這讓元件架構可以執行能力轉送。
用戶端元件會以靜態方式要求資訊清單 use 區段中的通訊協定。如果能力轉送成功，這會在用戶端的命名空間中建立 /svc/fuchsia.example.Foo 通訊協定項目。
供應商程式碼會在執行階段發布實作項目。這會在供應器的傳出目錄的 /svc/fuchsia.example.Foo 建立通訊協定項目。
用戶端程式碼會在執行階段與通訊協定控制代碼連線。這個動作會開啟 FIDL 連線，連結至在供應器元件中執行的實作。

發布通訊協定實作

實作 FIDL 通訊協定的元件會在其元件資訊清單中宣告並公開該通訊協定為能力。這可讓元件架構執行能力轉送，從這個元件到要求該能力的拓撲中的其他項目。

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

功能轉送會說明通訊協定的存取權限，但不會建立連線所需的端點。元件必須使用 fuchsia.io 通訊協定，將實作內容以 /svc/ 控制代碼發布至傳出目錄。產生的 FIDL 繫結會包裝此控點，並讓提供者連結要求控制代碼，以開始接收 FIDL 訊息。

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));

連線至通訊協定實作

用戶端元件會在其元件資訊清單中，將通訊協定宣告為必要能力。這可讓元件架構判斷元件是否有權存取通訊協定實作。如果路徑存在，元件的命名空間就會包含對應的 /svc/ 控制代碼。

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

用戶端元件使用 fuchsia.io 通訊協定與通訊協定實作建立連線，並開啟管道。產生的 FIDL 繫結會包裝這個管道，並讓用戶端開始傳送訊息至供應器。

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());

練習：Echo 伺服器和用戶端

在本節中，您將使用針對 fidl.examples.routing.echo 產生的 FIDL 繫結，在 Rust 中實作用戶端和伺服器元件。

啟動模擬器

如果您尚未有一個執行中的執行個體，請啟動模擬器：

啟動新的模擬器執行個體：

ffx emu start --headless

啟動完成後，模擬器會輸出下列訊息並傳回：

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.

啟動套件伺服器，讓模擬器載入軟體套件：
```
fx serve
```

建立伺服器元件

請先建立新的元件專案來實作 echo 伺服器。這個元件將提供 Echo 通訊協定並處理傳入要求。

在 //vendor/fuchsia-codelab 目錄中為名為 echo-server 的新元件建立專案鷹架：

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

將以下建構規則新增至 BUILD.gn 檔案，以便建構及套件伺服器元件：

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" ]
}

將 Echo 通訊協定宣告為伺服器元件提供的能力，並公開該通訊協定供父項運作領域使用：

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",
        },
    ],
}

實作伺服器

開啟主要來源檔案，並將匯入陳述式替換為下列程式碼：

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 繫結會產生以 FIDL library 命名的 Rust 程式庫 Crate。針對 fidl.examples.routing.echo 程式庫，產生的 Crate 名稱為 fidl_fidl_examples_routing_echo。詳情請參閱「Rust 繫結」。

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>

將下列程式碼新增至 main()，以提供 Echo 通訊協定：

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(())
}

這個程式碼會執行下列步驟來提供 Echo 通訊協定：

初始化 ServiceFs，然後在傳出目錄的 /svc/fidl.examples.routing.echo.Echo 底下新增項目。
提供目錄，然後開始監聽連入連線。
針對任何相符的 Echo 要求，將 handle_echo_request() 函式新增為要求處理常式。

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();
}

這個程式碼會執行下列步驟來提供 Echo 通訊協定：

初始化 ComponentContext，然後在傳出目錄的 /svc/fidl.examples.routing.echo.Echo 底下新增項目。
提供目錄，然後開始監聽連入連線。
針對任何相符的 Echo 要求，將 EchoImplementation 執行個體做為要求處理常式進行附加。

新增以下程式碼，實作通訊協定要求處理常式：

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 中的每個要求都會以方法名稱 (EchoString) 輸入，並附上回應器介面來傳回傳回值。

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_;
};

每個 Echo 通訊協定方法都有對應的覆寫函式 (EchoString())，並提供可傳回傳回值的回呼介面。

這種實作方式會直接「echo」在回應酬載中從要求傳回相同的字串值。

建立用戶端元件

建立另一個元件專案以實作 echo 用戶端。這個元件會連線至通訊協定實作並傳送要求。

在 //vendor/fuchsia-codelab 目錄中為名為 echo-client 的新元件建立專案鷹架：

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

在 BUILD.gn 檔案中加入以下建構規則，即可建構及套件用戶端元件：

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" ]
}

設定用戶端的元件資訊清單，以要求伺服器公開的 fidl.examples.routing.echo.Echo 能力：

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" },
    ],
}

實作用戶端

與 echo-args 類似，用戶端會將程式引數做為訊息傳送至伺服器。在 echo_client.cml 中新增下列程式引數：

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!" ],
},

開啟主要來源檔案，並將匯入陳述式替換為以下程式碼：

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>

將下列程式碼新增至 main()，以便連線至 Echo 通訊協定並傳送要求：

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 提供包裝函式，可依名稱連線至已公開的能力，並將控制代碼傳回至已開啟的 EchoProxy 介面。這個 Proxy 包含 echo_string() FIDL 通訊協定方法。

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 提供包裝函式，可依名稱連線至已公開的能力，並將控制代碼傳回開啟 Proxy 介面。這個 Proxy 包含 EchoString() FIDL 通訊協定方法。

整合元件

伺服器提供的功能必須透過元件架構轉送至用戶端。如要啟用這項功能，您須實作運作領域元件做為父項，並管理能力轉送。

針對領域產品定義建立新的專案目錄：

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

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

使用下列內容建立新的元件資訊清單檔案 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",
            ],
        },
    ],
}

這項操作會建立具有伺服器和用戶端的元件運作領域做為子項元件，並將 fidl.examples.routing.echo.Echo 通訊協定能力轉送至用戶端。

新增 BUILD.gn 檔案，為領域元件建立建構目標：

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",
  ]
}

更新建構設定，加入新元件：

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

再次執行 fx build 以建構元件：

fx build

將元件新增至拓撲

您會將元件新增至 ffx-laboratory，這是在產品「核心領域」中用於開發作業的受限集合。集合可讓在執行階段動態建立及刪除元件。

如要建立元件執行個體，請將 echo-realm 元件網址和 ffx-laboratory 中的適當路徑名稱傳遞至 ffx component create：

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

然後，使用 ffx component resolve 解析 echo-realm 元件：

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

使用 ffx component show 驗證伺服器和用戶端的執行個體是否已建立為子項元件：

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

驗證元件互動

使用 ffx component start 啟動現有的用戶端元件執行個體：

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

開啟另一個終端機視窗，並驗證用戶端元件的輸出記錄：

ffx log --filter echo

裝置記錄中應會顯示下列輸出內容：

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

伺服器元件會在用戶端與 fidl.examples.routing.echo.Echo 能力連線後啟動，並繼續提供其他 FIDL 要求。

請使用 ffx component show 查看在元件執行個體樹狀結構中執行的 echo 伺服器：

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

刪除執行個體

使用下列指令清除 echo-realm 例項：

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

Fuchsia 介面定義語言

整合測試