Write your .proto file

.proto is a file which contains all definition of the gRPC service and the method request and response types using the format of protocol buffers.

Under the workspace, we create folders src/main/proto and create our .proto file, calculator.proto.

cd ~/grpclab
mkdir -p src/main/proto
nano src/main/proto/calculator.proto

calculator.proto

syntax = "proto3";

package calculator;
option java_package = "cslab.grpclab";

// define 2 rpcs for Calculator service
service Calculator {
    rpc Sum(CalculationRequest) returns(CalculationRespond) {};
    rpc Product(CalculationRequest) returns(CalculationRespond) {};
}

//Define the structure of `CalculationRequest` which is the input of the rpcs
message CalculationRequest {
    float a = 1;
    float b = 2;
}

//Define the structure of `CalculationRequest` which is the output of the rpcs
message CalculationRespond {
    float result = 1;
}