import com.google.iot.m2m.LocalEndpointManager;
import com.google.iot.m2m.Client;
import com.google.iot.m2m.Transaction;
import com.google.iot.m2m.Message;

public class Main {

    public static void main(String[] args)
    {
        System.out.println("Hello coap!");

        LocalEndpointManager manager = new LocalEndpointManager();

        Client client = new Client(manager, "coap://coap.me/test");

        Transaction transaction = client.newRequestBuilder().send();

        Message response = transaction.getResponse();

        System.out.println("Got response: " + response);
    }

}

Information:java: Errors occurred while compiling module 'testCoapBluster.testCoap.main'
Information:javac 1.8.0_201 was used to compile java sources
Information:2/28/19 9:42 AM - Compilation completed with 10 errors and 0 warnings in 1 s 635 ms
/home/michael_k/IdeaProjects/testCoap/src/main/java/Main.java
Error:(1, 26) java: package com.google.iot.m2m does not exist
Error:(2, 26) java: package com.google.iot.m2m does not exist
Error:(3, 26) java: package com.google.iot.m2m does not exist
Error:(4, 26) java: package com.google.iot.m2m does not exist
Error:(12, 9) java: cannot find symbol
  symbol:   class LocalEndpointManager
  location: class Main
Error:(12, 44) java: cannot find symbol
  symbol:   class LocalEndpointManager
  location: class Main
Error:(14, 9) java: cannot find symbol
  symbol:   class Client
  location: class Main
Error:(14, 29) java: cannot find symbol
  symbol:   class Client
  location: class Main
Error:(16, 9) java: cannot find symbol
  symbol:   class Transaction
  location: class Main
Error:(18, 9) java: cannot find symbol
  symbol:   class Message
  location: class Main

plugins {
    id 'java'
}

group 'testCoapBluster'
version '1.0-SNAPSHOT'

sourceCompatibility = 1.8

repositories {
    mavenCentral()
}

dependencies {
    testCompile group: 'junit', name: 'junit', version: '4.12'
    compile 'com.google.iot.coap:coap:0.01.00'
}

public class MainActivity extends AppCompatActivity {
    final String TAG = "coap";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        final Button server = findViewById(R.id.server);
        server.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startServer();
            }
        });

        final Button client = findViewById(R.id.client);
        client.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                startClient();
            }
        });
    }

    private void startClient() {
        try {
            LocalEndpointManager manager = new LocalEndpointManager();
            Client client = new Client(manager, "coap://127.0.0.1/test/hello");
            Transaction transaction = client.newRequestBuilder().send();
            Message response = transaction.getResponse(5000);
            Log.e(TAG, "Got response: " + response.getPayloadAsString());
        }
        catch (Exception exception) {
            Log.e(TAG, "Client.Exception->" + exception.toString());
        }
    }

    private void startServer() {
        try {
            LocalEndpointManager manager = new LocalEndpointManager();
            Server server = new Server(manager);
            LocalEndpoint udpEndpoint = manager.getLocalEndpointForScheme(Coap.SCHEME_UDP);
            server.addLocalEndpoint(udpEndpoint);
            Resource<InboundRequestHandler> rootResource = new Resource<>();
            Resource<InboundRequestHandler> testFolder = new Resource<>();
            InboundRequestHandler helloHandler = new InboundRequestHandler() {
                public void onInboundRequest(InboundRequest inboundRequest) {
                    inboundRequest.sendSimpleResponse(Code.RESPONSE_CONTENT, "Hello, World!");
                }
            };
            testFolder.addChild("hello", helloHandler);
            rootResource.addChild("test", testFolder);
            server.setRequestHandler(rootResource);
            server.start();
            Log.e(TAG, "Server started");
        }
        catch (Exception exception) {
            Log.e(TAG, "Server.Exception->" + exception.toString());
        }
    }
}