RPC概念学习笔记

• RPC是是什么

• Remote procedure call -远程过程调用 对应与本地过程调用也就是本地方法调用
• 它本身并不是一个具体的协议，而是一种调用方式。

• TCP 粘包

• 什么是粘包:TCP面向字节流,没有内容分割符,可能将两条消息同时从缓存区读出来.发送两条消息 1:这是李东 2:**亚**健康终结者.接收端可能会接收到1:这是李东**亚** 2:健康终结者.如果没有正确的读取字节的话
• 怎么解决:通过分隔符or定义消息长度等.
• 直接使用TCP,需要去定义消息边界和格式,要解决这个通用的问题,所以一般的应用不会直接在TCP上构建自己的应用层协议.
• 演示demo

• 服务端

public class ServerDemo {
    public static void main(String[] args) throws IOException {
        // Create a server socket on port 1234
        ServerSocket serverSocket = new ServerSocket(1234);
        // Wait for a client to connect
        Socket clientSocket = serverSocket.accept();
        // Create input and output streams for the client socket
        BufferedReader in = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        PrintWriter out = new PrintWriter(clientSocket.getOutputStream(), true);
        // Read input from the client and send a response
        String inputLine = "";
        char[] buffer = new char[5];
        int bytesRead;
        while ((bytesRead = in.read(buffer)) != -1) {
            inputLine = new String(buffer, 0, bytesRead);
            System.out.println("received "+ inputLine);
            out.println("Server received: " + inputLine);
        }
        // Close the streams and sockets
        out.close();
        in.close();
        clientSocket.close();
        serverSocket.close();
    }
}

• 客户端

public class ClientDemo {
    public static void main(String[] args) throws IOException {
        // Create a socket to connect to the server on port 1234
        Socket socket = new Socket("localhost", 1234);
        
        // Create input and output streams for the socket
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
        
        // Send a message to the server
        out.printf("这是李东");
        out.printf("亚健康终结者");
//        out.println("Hello, server!");
        // Read the server's response
        String inputLine;
        while ((inputLine = in.readLine()) != null) {
            System.out.println("get response = "+inputLine);
        }
        // Close the streams and socket
        out.close();
        in.close();
        socket.close();
    }
}

RPC框架使用

• IDL : Interface Definition Language

• Proto

• syntax = "proto3";
  option java_multiple_files = true;
  option java_package = "io.grpc.examples.helloworld";
  option java_outer_classname = "HelloWorldProto";
  option objc_class_prefix = "HLW";
  package helloworld;
  // The greeting service definition.
  service Greeter {
    // Sends a greeting
    rpc SayHello (HelloRequest) returns (HelloReply) {}
  }
  // The request message containing the user's name.
  message HelloRequest {
    string name = 1;
  }
  // The response message containing the greetings
  message HelloReply {
    string message = 1;
  }

• AIDL

• RPC和HTTP的区别

• RPC是一种思想,比HTTP出现的早
• HTTP是一种协议

RPC的使用场景是是什么

• HTTP 浏览器->服务器
• RPC 客户端->服务器
• RPC在服务端内部集群
• Android的RPC

• 常见的RPC框架和实现方式

• Dubbo 基于TCP,性能更好,可定制
• gRPC 基于HTTP,兼容性更好.

• RPC的优势

• 像调用本地方法一样调用

• gPRC

channel = ManagedChannelBuilder.forAddress(host, port).usePlaintext().build();
GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(channel);
HelloRequest request = HelloRequest.newBuilder().setName(message).build();
HelloReply reply = stub.sayHello(request);
return reply.getMessage();

• Android上的RPC

val clipboard: ClipboardManager =            getContext().getSystemService(Context.CLIPBOARD_SERVICE) as ClipboardManager 
          val clip = ClipData.newPlainText("label", "text")
          clipboard.setPrimaryClip(clip)

• 使用IDL定义方法-能够在编译时,检测出类型错误

• 总结

• 应该说RPC和HTTP应该不是同一个概念层次上的东西
• RPC是一种调用方式,可以基于HTTP,TCP,UDP.常见的RPC应该算是一种框架,包含服务发现,注册等功能

参考

• Build client-server applications with gRPC