Listen to gRPC requests

index.js

function main() {
  const server = new grpc.Server();
  server.addService(calculatorProto.Calculator.service, {calculate});
  server.bindAsync(`0.0.0.0:${PORT}`, grpc.ServerCredentials.createInsecure(), (error, port) => {
    if (error) {
      throw error;
    }
    server.start();
  });
}