.netcore grpc服务端流方法详解

一、服务端流式处理概述

客户端向服务端发送请求，服务端可以将多个消息流式传输回调用方
和客户端流相反，客户端流发出请求，服务端可以传输一批消息给客户端，直至本次请求响应完全结束。
针对文件分段传输下载，该方式非常有用。

二、案例介绍

提供一个一元方法查询文件
提供一个文件流传输的服务端流式方法，进行文件流推送

三、服务端配置（注意：grpc相关配置参考我之前的文章）

// 1.提供公共的实体proto文件
// 2.服务引用对应的proto文件
// 3.定义三个客户流方法


syntax = "proto3";

option csharp_namespace = "GrpcProject";

package grpc.serviceing;


// 服务端流对应的请求流和响应流

message FileInfoRequest
{
	string fileName = 1;
}

message FileInfoResponse
{
	string fileName = 1;
	int64 fileSize = 2;
	string extension = 3;
}

message ProgressBarResponse
{
	FileInfoResponse fileMessage = 1;
	bytes fileBytes = 2;
}







// serverstream.proto定义service方法


syntax = "proto3";

import "google/protobuf/empty.proto";
import "Protos/messages.proto";

option csharp_namespace = "GrpcProject";

package grpc.serviceing;

service ServerStreamRpc{
	// 一元文件获取展示
	rpc GetFileMessage(google.protobuf.Empty) returns (FileInfoResponse);
	// 服务端文件流处理
	rpc StreamingFromServer	(FileInfoRequest) returns (stream ProgressBarResponse);
}

服务接口实现：

    public class ServerStreamService : ServerStreamRpc.ServerStreamRpcBase
    {
        /// <summary>
        /// 获取文件信息
        /// </summary>
        /// <param name="request">空请求</param>
        /// <param name="context">服务调用上下文</param>
        /// <returns></returns>
        public override Task<FileInfoResponse> GetFileMessage(Empty request, ServerCallContext context)
        {
            var filePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Files", "cn-Liang-y.rar");

            FileInfo fileInfo = new FileInfo(filePath);
            FileInfoResponse fileInfoResponse = new FileInfoResponse();
            fileInfoResponse.FileName = fileInfo.Name;
            fileInfoResponse.FileSize = fileInfo.Length;
            fileInfoResponse.Extension = fileInfo.Extension;

            return Task.FromResult(fileInfoResponse);
        }

        public override async Task StreamingFromServer(FileInfoRequest request,
                                                 IServerStreamWriter<ProgressBarResponse> responseStream,
                                                 ServerCallContext context)
        {

            var filePath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Files", request.FileName);
            if (!File.Exists(filePath))
            {
                throw new FileNotFoundException(nameof(filePath));
            }

            // 进度条按照 100百分比进行划分
            FileInfo fileInfo = new FileInfo(filePath);

            using var fileStream = fileInfo.OpenRead();
            // 插入固定长度

            int fixedLength = (int)fileStream.Length / 100;
            byte[] fileBytes = new byte[fixedLength];
            int len;
            while ((len = fileStream.Read(fileBytes, 0, fixedLength)) > 0)
            {
                await Console.Out.WriteLineAsync($"打印字节长度：{len}");
                var response = new ProgressBarResponse();
                response.FileMessage = new FileInfoResponse
                {
                    FileName = fileInfo.Name,
                    FileSize = fileInfo.Length,
                    Extension = fileInfo.Extension
                };
                response.FileBytes = ByteString.CopyFrom(fileBytes);
                await responseStream.WriteAsync(response);
            }

        }
    }

Program注入：

    public class Program
    {
        public static void Main(string[] args)
        {
            var builder = WebApplication.CreateBuilder(args);
            builder.Services.AddGrpc();
            var app = builder.Build();
            // 一元方法
            //app.MapGrpcService<DollarService>();
            // 客户端流
            //app.MapGrpcService<ClientStreamService>();
            // 服务端流
            app.MapGrpcService<ServerStreamService>();
            app.Run();
        }
    }

四、客户端配置

引用proto文件，配置为客户端类型
根据编译生成的函数进行传参调用
创建WPF客户端提供控制条显示

button按钮触发grpc

        private async void download_Click(object sender, RoutedEventArgs e)
        {
            Action<int> action = async i =>
            {
                progressBar.Value = i;
                await Task.Delay(100);
            };

            await WpfClient.Show(action);
        }

grpc客户端接口调用

    public class WpfClient
    {
        public static async Task Show(Action<int> action)
        {

            var channel = GrpcChannel.ForAddress("https://localhost:7188");


            var client = new GrpcProject.ServerStreamRpc.ServerStreamRpcClient(channel);

            var fileMessage = await client.GetFileMessageAsync(new Google.Protobuf.WellKnownTypes.Empty());

            FileInfoRequest request = new FileInfoRequest();
            request.FileName = fileMessage.FileName;

            var streaming = client.StreamingFromServer(request);

            var path = Path.Combine(Directory.GetCurrentDirectory(), "test.rar");

            using var stream = new FileStream(path, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.ReadWrite);
            int i = 0;
            await foreach (var item in streaming.ResponseStream.ReadAllAsync())
            {
                stream.Write(item.FileBytes.Span);
                action(i++);
            }
            stream.Flush();
            stream.Close();
        }
    }