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Posted 5 Mar 2012
Licenced CPOL

Android: How to communicate with .NET application via TCP

, 6 Mar 2012
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Simple example showing how to communicate between Android and .NET application.
This is an old version of the currently published article.


The example bellow implements a simple request-response communication between Android and .NET application. The Android application is a simple client using the .NET application as a service to calculate length of the text message.

The example bellow uses Eneter Messaging Framework making the whole communication very simple. (The framework is free for non-commercial use and can be downloaded from You need to download Eneter for.NET and Eneter for Android. More detailed technical info can be found at technical info.)


TCP on Android

When you implement the communication via TCP on Android, you must count with two specifics:

  1. You must set INTERNET permission for your Android application!
  2. If the permission is not set, the application is not allowed to communicate across the network. To set the INTERNET permission you must add the following line to AndroidManifest.xml.

    <uses-permission android:name="android.permission.INTERNET"/>

    An example of AndroidManifest.xml allowing communication across the network:

    <?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android=""
        android:versionName="1.0" >
        <uses-sdk android:minSdkVersion="7" />
        <uses-permission android:name="android.permission.INTERNET"/>
            android:label="@string/app_name" >
                android:label="@string/app_name" >
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
  3. The IP address (loopback) cannot be set on the Android emulator to communicate with the .NET application!
  4. The emulator acts as a separate device. Therefore, the IP address is the loopback of that device and cannot be used for the communication with other applications running on the same computer as the emulator.

    Instead of that you must use a real IP address of the computer or the emulator can use the special address that is routed to (loopback) on the computer. In my example, the Android emulator uses and  the .NET service is listening to

Android Client Application

The Android client is a very simple application allowing user to put some text message and send the request to the service to get back the length of the text. When the response message is received it must be marshalled to the UI thread to display the result. Also please do not forget to set android.permission.INTERNET.

The whole implementation is very simple with using the Eneter framework:

package net.client;

import eneter.messaging.diagnostic.EneterTrace;
import eneter.messaging.endpoints.typedmessages.*;
import eneter.messaging.messagingsystems.messagingsystembase.*;
import eneter.messaging.messagingsystems.tcpmessagingsystem.TcpMessagingSystemFactory;
import android.os.Bundle;
import android.os.Handler;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.*;

public class AndroidNetCommunicationClientActivity extends Activity
    // Request message type
    // The message must have the same name as declared in the service.
    // Also, if the message is the inner class, then it must be static.
    public static class MyRequest
        public String Text;

    // Response message type
    // The message must have the same name as declared in the service.
    // Also, if the message is the inner class, then it must be static.
    public static class MyResponse
        public int Length;
    // UI controls
    private Handler myRefresh = new Handler();
    private EditText myMessageTextEditText;
    private EditText myResponseEditText;
    private Button mySendRequestBtn;
    // Sender sending MyRequest and as a response receiving MyResponse.
    private IDuplexTypedMessageSender<MyResponse, MyRequest> mySender;
    /** Called when the activity is first created. */
    public void onCreate(Bundle savedInstanceState)
        // Get UI widgets.
        myMessageTextEditText = (EditText) findViewById(;
        myResponseEditText = (EditText) findViewById(;
        mySendRequestBtn = (Button) findViewById(;
        // Subscribe to handle the button click.
        catch (Exception err)
            EneterTrace.error("Open connection failed.", err);
    public void onDestroy()
        // Stop listening to response messages.
    private void openConnection() throws Exception
        // Create sender sending MyRequest and as a response receiving MyResponse
        IDuplexTypedMessagesFactory aSenderFactory =
           new DuplexTypedMessagesFactory();
        mySender = aSenderFactory.createDuplexTypedMessageSender(MyResponse.class, MyRequest.class);
        // Subscribe to receive response messages.
        // Create TCP messaging for the communication.
        // Note: is a special alias to the loopback (
        //       on the development machine
        IMessagingSystemFactory aMessaging = new TcpMessagingSystemFactory();
        IDuplexOutputChannel anOutputChannel = 
        // Attach the output channel to the sender and be able to send
        // messages and receive responses.
    private void onSendRequest(View v)
        // Create the request message.
        MyRequest aRequestMsg = new MyRequest();
        aRequestMsg.Text = myMessageTextEditText.getText().toString();
        // Send the request message.
        catch (Exception err)
            EneterTrace.error("Sending the message failed.", err);
    private void onResponseReceived(Object sender, final TypedResponseReceivedEventArgs<MyResponse> e)
        // Display the result - returned number of characters.
        // Note: Marshal displaying to the correct UI thread. Runnable()
                public void run()
    private EventHandler<TypedResponseReceivedEventArgs<MyResponse>> myOnResponseHandler
         = new EventHandler<TypedResponseReceivedEventArgs<MyResponse>>()
        public void onEvent(Object sender,
                            TypedResponseReceivedEventArgs<MyResponse> e)
            onResponseReceived(sender, e);
    private OnClickListener myOnSendRequestClickHandler = new OnClickListener()
        public void onClick(View v)

.NET Service Application

The .NET service is a simple console application listening to TCP and receiving requests to calculate the length of a given text.

The implementation of the service is very simple:

using System;
using Eneter.Messaging.EndPoints.TypedMessages;
using Eneter.Messaging.MessagingSystems.MessagingSystemBase;
using Eneter.Messaging.MessagingSystems.TcpMessagingSystem;

namespace ServiceExample
    // Request message type
    public class MyRequest
        public string Text { get; set; }

    // Response message type
    public class MyResponse
        public int Length { get; set; }

    class Program
        private static IDuplexTypedMessageReceiver<MyResponse, MyRequest> myReceiver;

        static void Main(string[] args)
            // Create message receiver receiving 'MyRequest' and receiving 'MyResponse'.
            IDuplexTypedMessagesFactory aReceiverFactory = new DuplexTypedMessagesFactory();
            myReceiver = aReceiverFactory.CreateDuplexTypedMessageReceiver<MyResponse, MyRequest>();

            // Subscribe to handle messages.
            myReceiver.MessageReceived += OnMessageReceived;

            // Create TCP messaging.
            IMessagingSystemFactory aMessaging = new TcpMessagingSystemFactory();
            IDuplexInputChannel anInputChannel = 

            // Attach the input channel and start to listen to messages.

            Console.WriteLine("The service is running. To stop press enter.");

            // Detach the input channel and stop listening.
            // It releases the thread listening to messages.

        // It is called when a message is received.
        private static void OnMessageReceived(object sender, 
              TypedRequestReceivedEventArgs<MyRequest> e)
            Console.WriteLine("Received: " + e.RequestMessage.Text);

            // Create the response message.
            MyResponse aResponse = new MyResponse();
            aResponse.Length = e.RequestMessage.Text.Length;

            // Send the response message back to the client.
            myReceiver.SendResponseMessage(e.ResponseReceiverId, aResponse);

And here are applications communicating together:



This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


About the Author

Slovakia Slovakia
My programming path started in 1987 when I got my first computer Sharp MZ-800.
It came with 8 bit CPU Z80, 64Kb RAM and the tape recorder. It was a great machine. I think I still have it somewhere.
I was fascinated and I started to write first programs. Eventually I became developer and software architect. I like innovations and clean nice solutions.

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QuestionAny way refresh communication if C# app restarted? Pin
patongjs29-Mar-18 20:07
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GeneralMy vote of 5 Pin
DrABELL6-Dec-17 22:56
professionalDrABELL6-Dec-17 22:56 
GeneralMessage Closed Pin
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GeneralMessage Closed Pin
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QuestionTransferring files via TCP Pin
ArunHanu15-Jun-17 22:26
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QuestionImage transferring by eneter messaging Pin
Hamza Saleem13-May-17 9:50
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AnswerRe: Image transferring by eneter messaging Pin
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Question.NET as client Pin
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AnswerRe: .NET as client Pin
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QuestionCommunication Problem Pin
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Questionsend an image rather than a text ? Pin
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GeneralRe: send an image rather than a text ? Pin
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