//Project的build.gradle中添加rotobuf-gradle-plugin插件
buildscript {
 ...
 dependencies {
 ...
 classpath "com.google.protobuf:protobuf-gradle-plugin:0.8.0"
 ...
 }
 ...
}

//App的build.gradle中添加下面配置
apply plugin: 'com.google.protobuf'

protobuf {
 protoc {
 artifact = 'com.google.protobuf:protoc:3.0.0'
 }
 plugins {
 javalite {
  artifact = "com.google.protobuf:protoc-gen-javalite:3.0.0"
 }
 grpc {
  artifact = 'io.grpc:protoc-gen-grpc-java:1.0.0' // CURRENT_GRPC_VERSION
 }
 }
 generateProtoTasks {
 all().each { task ->
  task.plugins {
  javalite {}
  grpc {
   // Options added to --grpc_out
   option 'lite'
  }
  }
 }
 }
}

//App的build.gradle中添加下面配置
 dependencies {
 ...
 compile 'io.grpc:grpc-okhttp:1.1.2'
 compile 'io.grpc:grpc-protobuf-lite:1.1.2'
 compile 'io.grpc:grpc-stub:1.1.2'
 compile 'javax.annotation:javax.annotation-api:1.2'
 ...
}

configurations.all {
 resolutionStrategy.force 'com.google.code.findbugs:jsr305:3.0.1'
 }

Warning:Conflict with dependency ‘com.google.code.findbugs:jsr305'. Resolved versions for app (3.0.0) and test app (2.0.1) differ. See http://g.co/androidstudio/app-test-app-conflict for details.

android {
 ...
 configurations.all {
 resolutionStrategy.force 'com.google.code.findbugs:jsr305:3.0.1'
 }
 ...
}

public class MainActivity extends AppCompatActivity {
 private static final String TAG = "GrpcDemo";

 private static final int PROT = 55055;
 private static final String NAME = "linjw";
 private static final String HOST = "localhost";

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);

 startServer(PROT);
 startClient(HOST, PROT, NAME);
 }

 private void startServer(int port){
 try {
  Server server = ServerBuilder.forPort(port)
   .addService(new GreeterImpl())
   .build()
   .start();
 } catch (IOException e) {
  e.printStackTrace();
  Log.d(TAG, e.getMessage());
 }
 }

 private void startClient(String host, int port, String name){
 new GrpcTask(host, port, name).execute();
 }

 private class GreeterImpl extends GreeterGrpc.GreeterImplBase {
 public void sayHello(HelloRequest request, StreamObserver<HelloReply> responseObserver) {
  responseObserver.onNext(sayHello(request));
  responseObserver.onCompleted();
 }

 private HelloReply sayHello(HelloRequest request) {
  return HelloReply.newBuilder()
   .setMessage("hello "+ request.getName())
   .build();
 }
 }

 private class GrpcTask extends AsyncTask<Void, Void, String> {
 private String mHost;
 private String mName;
 private int mPort;
 private ManagedChannel mChannel;

 public GrpcTask(String host, int port, String name) {
  this.mHost = host;
  this.mName = name;
  this.mPort = port;
 }

 @Override
 protected void onPreExecute() {
 }

 @Override
 protected String doInBackground(Void... nothing) {
  try {
  mChannel = ManagedChannelBuilder.forAddress(mHost, mPort)
   .usePlaintext(true)
   .build();
  GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(mChannel);
  HelloRequest message = HelloRequest.newBuilder().setName(mName).build();
  HelloReply reply = stub.sayHello(message);
  return reply.getMessage();
  } catch (Exception e) {
  StringWriter sw = new StringWriter();
  PrintWriter pw = new PrintWriter(sw);
  e.printStackTrace(pw);
  pw.flush();
  return "Failed... : " + System.lineSeparator() + sw;
  }
 }

 @Override
 protected void onPostExecute(String result) {
  try {
  mChannel.shutdown().awaitTermination(1, TimeUnit.SECONDS);
  } catch (InterruptedException e) {
  Thread.currentThread().interrupt();
  }
  Log.d(TAG, result);
 }
 }
}

Caused by: io.grpc.ManagedChannelProvider$ProviderNotFoundException: No functional server found. Try adding a dependency on the grpc-netty artifact

dependencies {
 ...
 compile 'io.grpc:grpc-netty:1.1.2'
 compile 'io.grpc:grpc-protobuf-lite:1.1.2'
 compile 'io.grpc:grpc-stub:1.1.2'
 compile 'javax.annotation:javax.annotation-api:1.2'
 ...
}

com.android.build.api.transform.TransformException: com.android.builder.packaging.DuplicateFileException: Duplicate files copied in APK META-INF/INDEX.LIST

android {
 ...
 packagingOptions {
 pickFirst 'META-INF/INDEX.LIST'
 pickFirst 'META-INF/LICENSE'
 pickFirst 'META-INF/io.netty.versions.properties'
 }
 ...
}

03-03 00:04:20.000 6137-6137/linjw.com.grpcdemo D/GrpcDemo: hello linjw

// Copyright 2015, Google Inc.
// All rights reserved.
//
// redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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;

import "google/protobuf/any.proto";

// The greeting service definition.
service Greeter {
 // Sends a greeting
 rpc SayHello (google.protobuf.Any) 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;
}

google/protobuf/any.proto: File not found.
helloworld.proto: Import “google/protobuf/any.proto” was not found or had errors.
helloworld.proto:44:17: “google.protobuf.Any” is not defined.

dependencies {
 ...
 compile 'io.grpc:grpc-netty:1.1.2'
 compile 'io.grpc:grpc-protobuf:1.1.2'
 compile 'io.grpc:grpc-stub:1.1.2'
 compile 'javax.annotation:javax.annotation-api:1.2'
 ...
}

protobuf {
 protoc {
  artifact = 'com.google.protobuf:protoc:3.0.0'
 }
 plugins {
  grpc {
   artifact = 'io.grpc:protoc-gen-grpc-java:1.0.0' // CURRENT_GRPC_VERSION
  }
 }
 generateProtoTasks {
  all().each { task ->
   task.builtins {
    java {}
   }
   task.plugins {
    grpc {}
   }
  }
 }
}

public class MainActivity extends AppCompatActivity {
 private static final String TAG = "GrpcDemo";

 private static final int PROT = 55055;
 private static final String NAME = "linjw";
 private static final String HOST = "localhost";

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);

  startServer(PROT);
  startClient(HOST, PROT, NAME);
 }

 private void startServer(int port){
  try {
   Server server = ServerBuilder.forPort(port)
     .addService(new GreeterImpl())
     .build()
     .start();
  } catch (IOException e) {
   e.printStackTrace();
   Log.d(TAG, e.getMessage());
  }
 }

 private void startClient(String host, int port, String name){
  new GrpcTask(host, port, name).execute();
 }

 private class GreeterImpl extends GreeterGrpc.GreeterImplBase {
  public void sayHello(Any request, StreamObserver<HelloReply> responseObserver) {
   try {
    responseObserver.onNext(sayHello(request.unpack(HelloRequest.class)));
    responseObserver.onCompleted();
   } catch (InvalidProtocolBufferException e) {
    e.printStackTrace();
   }
  }

  private HelloReply sayHello(HelloRequest request) {
   return HelloReply.newBuilder()
     .setMessage("hello "+ request.getName())
     .build();
  }
 }

 private class GrpcTask extends AsyncTask<Void, Void, String> {
  private String mHost;
  private String mName;
  private int mPort;
  private ManagedChannel mChannel;

  public GrpcTask(String host, int port, String name) {
   this.mHost = host;
   this.mName = name;
   this.mPort = port;
  }

  @Override
  protected void onPreExecute() {
  }

  @Override
  protected String doInBackground(Void... nothing) {
   try {
    mChannel = ManagedChannelBuilder.forAddress(mHost, mPort)
      .usePlaintext(true)
      .build();
    GreeterGrpc.GreeterBlockingStub stub = GreeterGrpc.newBlockingStub(mChannel);
    HelloRequest message = HelloRequest.newBuilder().setName(mName).build();
    HelloReply reply = stub.sayHello(Any.pack(message));
    return reply.getMessage();
   } catch (Exception e) {
    StringWriter sw = new StringWriter();
    PrintWriter pw = new PrintWriter(sw);
    e.printStackTrace(pw);
    pw.flush();
    return "Failed... : " + System.lineSeparator() + sw;
   }
  }

  @Override
  protected void onPostExecute(String result) {
   try {
    mChannel.shutdown().awaitTermination(1, TimeUnit.SECONDS);
   } catch (InterruptedException e) {
    Thread.currentThread().interrupt();
   }
   Log.d(TAG, result);
  }
 }
}