因为Grpc采用HTTP/2作为通信协议，默认采用LTS/SSL加密方式传输，比如使用.net core启动一个服务端（被调用方）时：
public static IHostBuilder CreateHostBuilder(string[] args) => Host.CreateDefaultBuilder(args) .ConfigureWebHostDefaults(webBuilder => { webBuilder.ConfigureKestrel(options => { options.ListenAnyIP(5000, listenOptions => { listenOptions.Protocols = HttpProtocols.Http2; listenOptions.UseHttps("xxxxx.pfx", "password"); }); }); webBuilder.UseStartup<Startup>(); });
其中使用UseHttps方法添加证书和秘钥。
但是，有时候，比如开发阶段，我们可能没有证书，或者是一个自己制作的临时测试证书，那么在客户端（调用方）调用是可能就会出现下面的异常：
Call failed with gRPC error status. Status code: 'Internal', Message: 'Error starting gRPC call. HttpRequestException: The SSL connection could not be established, see inner exception. AuthenticationException: The remote certificate is invalid according to the validation procedure.'. fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1] An unhandled exception has occurred while executing the request. Grpc.Core.RpcException: Status(StatusCode="Internal", Detail="Error starting gRPC call. HttpRequestException: The SSL connection could not be established, see inner exception. AuthenticationException: The remote certificate is invalid according to the validation procedure.", DebugException="System.Net.Http.HttpRequestException: The SSL connection could not be established, see inner exception. ---> System.Security.Authentication.AuthenticationException: The remote certificate is invalid according to the validation procedure. at System.Net.Security.SslStream.StartSendAuthResetSignal(ProtocolToken message, AsyncProtocolRequest asyncRequest, ExceptionDispatchInfo exception) at System.Net.Security.SslStream.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslStream.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslStream.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslStream.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslStream.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslStream.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslStream.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslStream.ProcessReceivedBlob(Byte[] buffer, Int32 count, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslStream.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest) at System.Net.Security.SslStream.PartialFrameCallback(AsyncProtocolRequest asyncRequest) --- End of stack trace from previous location where exception was thrown --- at System.Net.Security.SslStream.ThrowIfExceptional() at System.Net.Security.SslStream.InternalEndProcessAuthentication(LazyAsyncResult lazyResult) at System.Net.Security.SslStream.EndProcessAuthentication(IAsyncResult result) at System.Net.Security.SslStream.EndAuthenticateAsClient(IAsyncResult asyncResult) ..........
然而我们可能没有办法得到有效的证书，这时，我们有两个办法：
1、使用http协议
想想，我们为什么要使用Grpc？因为高性能，高效率，简单易用吧，但是https相比http就是多个加密的过程，这可能会有一定的性能损失（一般可忽略）。
而一般的，我们在微服务架构中使用Grpc比较多，而微服务一般部署在我们自己的一个子网下，这也就没必要使用https了吧？
首先我们知道，Grpc是基于HTTP/2作为通信协议的，而HTTP/2默认是基于LTS/SSL加密技术的，或者说默认需要https协议支持（https=http+lts/ssl），而HTTP/2又支持明文传输，即对http也是支持，但是一般需要我们自己去设置。
当我们使用Grpc时，又不去改变这个默认行为，那可能就会导致上面的报错。
在.net core开发中，Grpc要支持http，我们需要显示的指定不需要TLS支持，官方给出的做法是添加如下配置（比如客户端（调用方）在ConfigureServices添加）：
public void ConfigureServices(IServiceCollection services) { //显式的指定HTTP/2不需要TLS支持 AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2UnencryptedSupport", true); AppContext.SetSwitch("System.Net.Http.SocketsHttpHandler.Http2Support", true); services.AddGrpcClient<Greeter.GreeterClient>(nameof(Greeter.GreeterClient), options => { options.Address = new Uri("http://localhost:5000"); }); ... }
2、调用时不对证书进行验证
如果是控制台程序，我们可以这么做：
public static void Main(string[] args) { var channel = GrpcChannel.ForAddress("https://localhost:5000", new GrpcChannelOptions() { HttpClient = null, HttpHandler = new HttpClientHandler { //方法一 ServerCertificateCustomValidationCallback = HttpClientHandler.DangerousAcceptAnyServerCertificateValidator //方法二 //ServerCertificateCustomValidationCallback = (a, b, c, d) => true } }); var client = new Greeter.GreeterClient(channel); var result = client.SayHello(new HelloRequest() { Name = "Grpc" }); }
其中 HttpClientHandler 的 ServerCertificateCustomValidationCallback 是对证书的自定义验证，上面给出了两种方式验证。
如果是.net core的webmvc或者webapi程序，因为.net core 3.x开始已经支持了Grpc的引入，所以我只需要在ConfigureServices中注入Grpc的客户端是进行设置：
public void ConfigureServices(IServiceCollection services) { services.AddGrpcClient<Greeter.GreeterClient>(nameof(Greeter.GreeterClient), options => { options.Address = new Uri("https://localhost:5000"); }).ConfigurePrimaryHttpMessageHandler(() => { return new HttpClientHandler { //方法一 ServerCertificateCustomValidationCallback = HttpClientHandler.DangerousAcceptAnyServerCertificateValidator //方法二 //ServerCertificateCustomValidationCallback = (a, b, c, d) => true }; }); ... }
因为.net core3.x中Grpc的使用是基于它的HttpClient机制，比如 AddGrpcClient 方法返回的就是一个 IHttpClientBuilder 接口对象，上面的配置我们还可以这么写：
public void ConfigureServices(IServiceCollection services) { services.AddGrpcClient<Greeter.GreeterClient>(nameof(Greeter.GreeterClient)); services.AddHttpClient(nameof(Greeter.GreeterClient), httpClient => { httpClient.BaseAddress = new Uri("https://localhost:5000"); }).ConfigurePrimaryHttpMessageHandler(() => { return new HttpClientHandler { //方法一 ServerCertificateCustomValidationCallback = HttpClientHandler.DangerousAcceptAnyServerCertificateValidator //方法二 //ServerCertificateCustomValidationCallback = (a, b, c, d) => true }; }); ... }
总之，不管怎么调用，机制都是一样的，最终都是像上面的客户端调用一样去创建Client，只要能理解就好了。
