Click here to Skip to main content
Click here to Skip to main content

A Voice Chat Application in C#

, 5 Jul 2007 CPOL
Rate this:
Please Sign up or sign in to vote.
In this article I will discuss a simple voice chat application. We will grab the audio from the microphone using DirectSound and transmit it in UDP packets.

Screenshot - VoiceChat.jpg


In this article, I will discuss a simple voice chat application. We will grab the audio from the microphone using DirectSound and transmit it in UDP packets. To make things interesting, I used G711 vocoder to compress the data before transmission. I won't discuss here how to capture the audio from microphone and play it back using DirectSound or how G711 is implemented. For all these things you can look into the references given at the end of this article. Before we go further, let's discuss the architecture of the application. We will use the following call messages between the parties.

|             Invite                | 

| --------------------------------> |

|               OK                  |

| <-------------------------------- |

|                                   |

| --------------------------------> |

|            Audio flow             |

| <-------------------------------- |

|               Bye                 | 

| --------------------------------> |

A                                   B

Using the code

Here are the commands for interaction between the two parties:

enum Command
    Invite, //Make a call.
    Bye,    //End a call.
    Busy,   //User busy.
    OK,     //Response to an invite message. OK is sent to 
            //indicate that call is accepted.
    Null,   //No command.

When the user wants to make a call, we send an Invite message and wait for an OK response. When we receive an OK, we start receiving/sending audio captured from the microphone. If the remote party rejects the call then a Busy response is sent. To drop a call, we simply send a Bye message. The application will asynchronously receive/send call messages on port 1450 and synchronously receive/send audio data on port 1550. In other words, the application listens on two ports: one for call messages and the other for audio data. I will now walk you through some code. When the application starts, we start listening for call messages on port 1450:

//Using UDP sockets
clientSocket = new Socket(AddressFamily.InterNetwork, 
EndPoint ourEP = new IPEndPoint(IPAddress.Any, 1450);

//Listen asynchronously on port 1450 for 
//coming messages (Invite, Bye, etc).

//Receive data from any IP.
EndPoint remoteEP = (EndPoint)(new IPEndPoint(IPAddress.Any, 0));
byteData = new byte[1024];

//Receive data asynchornously.
    0, byteData.Length,
    ref remoteEP,
    new AsyncCallback(OnReceive),

When we receive a message, we process it to see what type of message it is and act accordingly. Please see the OnReceive handler for it in the attached project files. To receive/send audio from a microphone, we start two threads so that the synchronous send/receive doesn't block our UI. This is done as follows, noting that the audio is received/sent on port 1550:

private void InitializeCall()
        //Start listening on port 1500.
        udpClient = new UdpClient(1550);
        Thread senderThread = new Thread(new ThreadStart(Send));
        Thread receiverThread = new Thread(new ThreadStart(Receive));
        bIsCallActive = true;

        //Start the receiver and sender thread.
        btnCall.Enabled = false;
        btnEndCall.Enabled = true;
    catch (Exception ex)
            "VoiceChat-InitializeCall ()", MessageBoxButtons.OK, 

The Send and Receive methods can be seen in the attached project; understanding them is easy.



  • 5 July, 2007 -- Original version posted


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


About the Author

Hitesh Sharma

United States United States
No Biography provided

Comments and Discussions

Questionconnection problem PinprofessionalMember 1043437817-Feb-14 5:25 
QuestionNoise PinmemberMember 88923497-Jan-14 2:32 
AnswerRe: Noise PinmemberZaryab Iftikhar27-May-14 6:55 
QuestionDirectX Problem PinmemberMember 1006022322-May-13 8:37 
AnswerRe: DirectX Problem PinmemberAletheuein3-Jun-13 3:17 
QuestionIs it possible to voice call to remote desktop using this code? Pinmemberrajesh@198910-Apr-13 4:17 
Questionmo me so rotto il cazzo PinmemberCrisLoveStefy1-Sep-12 23:23 
QuestionzxxczcZCZC Pinmembersaravanan33323-Aug-12 20:48 
Questionfor all Pinmemberkumeneger11-May-12 4:06 
AnswerRe: for all PinmemberHelldrake1-Jul-13 22:57 
BugProblem! PinmemberJrPacheco17-Apr-12 4:59 
Questiononly one usage of each socket address (protocol/network address/port) is normally permitted PinmemberMember 84226775-Apr-12 2:34 
Questionis it possible to encrypt a voice in your application? PinmemberThendral.N27-Mar-12 2:02 

i need to convert the voice using encryption and decrytion.
is it possible?
If it is means can you tell me the solution?
QuestionVoice chat application doesnt connect with another machine PinmemberThendral.N24-Jan-12 2:00 
Questiononly one usage of each socket address protocol network address port is normally permitted PinmemberThendral.N24-Jan-12 0:19 
QuestionSend message issue Pinmemberdanm3612-Jan-12 11:12 
Questionhi sir how can I add Microsoft.directx and Microsoft.directx .DirectSound and voicechat.vhost.exe.manifest refferance files tell me plz [modified] Pinmemberbahidab4-Jan-12 1:17 
QuestionQuerry.. PinmemberTarun Khatana14-Dec-11 9:45 
Generalno sound while lost focus PinmemberAkeeq14-Jun-11 2:39 
GeneralRe: no sound while lost focus PinmemberAkeeq16-Jun-11 21:40 
GeneralRe: no sound while lost focus Pinmemberharshad3654-Dec-12 18:43 
GeneralRe: no sound while lost focus PinmemberAkeeq11-Dec-12 1:52 
GeneralSound Quality PinmemberOblivion1707-Jun-11 6:51 
GeneralRe: Sound Quality Pinmemberbubifengyun7-Jan-13 17:36 
Questionhi Pinmembermaktumpashal22-May-11 3:15 
GeneralMDA LoaderLock Error; Error in Application PinmemberAkeeq13-May-11 20:36 
GeneralRe: MDA LoaderLock Error; Error in Application PinmemberAkeeq16-Jun-11 21:44 
GeneralMy vote of 5 PinmemberMember 446500731-Mar-11 15:29 
GeneralHi PinmemberKiya161-Mar-11 8:33 
Generali want to make it over internet Pinmembercrysis8928-Feb-11 12:28 
Generalerror Pinmembersamathu22-Feb-11 21:11 
Generalerror Pinmembersamathu21-Feb-11 5:19 
GeneralSome question PinmemberRezabest19-Jan-11 3:27 
GeneralMy vote of 3 Pinmemberlxxlxx4-Jan-11 3:09 
GeneralMuLawEncoder Vs ALawEncoder What's the difference Pinmemberjibin.mn30-Oct-10 1:09 
Generalerrors regarding the project "A Voice Chat Application in C#". Pinmemberhemendrapsingh28-Feb-10 10:17 
GeneralMy vote of 2 Pinmembersomireddy25-Feb-10 23:04 
GeneralCompact Framework Pinmembersonia108211-Jan-10 20:20 
QuestionError while calling on second time [modified] Pinmemberhiran53612-Oct-09 22:08 
Generalnot working in studio 2008 Pinmembersurpatel785-Oct-09 3:21 
AnswerRe: not working in studio 2008 PinmemberSmacky31125-May-10 4:44 
GeneralNotify Pinmembermayuwi1-Oct-09 16:12 
QuestionHow to select the device dynamically ? PinmemberJack98739-Sep-09 1:23 
AnswerRe: How to select the device dynamically ? Pinmembermayuwi1-Oct-09 14:52 
GeneralVoiveChat-InitializeCall() Only one usage of each socket address (protocol/ network address/ port) is nomally permitted Pinmemberaadiost24-Aug-09 3:49 
GeneralRe: VoiveChat-InitializeCall() Only one usage of each socket address (protocol/ network address/ port) is nomally permitted Pinmembersloaken6-Sep-09 22:18 
GeneralOnly one usage of each socket address(protocol/network address/port) is normally permitted Pinmembergoitom219-Aug-09 5:36 
GeneralRe: Only one usage of each socket address(protocol/network address/port) is normally permitted [modified] Pinmembersloaken6-Sep-09 10:49 
GeneralRe: Only one usage of each socket address(protocol/network address/port) is normally permitted Pinmembersurpatel785-Oct-09 3:48 
QuestionCan this project be ported for Compact Framework? Pinmemberm_mughalz18-Aug-09 20:55 

General General    News News    Suggestion Suggestion    Question Question    Bug Bug    Answer Answer    Joke Joke    Rant Rant    Admin Admin   

Use Ctrl+Left/Right to switch messages, Ctrl+Up/Down to switch threads, Ctrl+Shift+Left/Right to switch pages.

| Advertise | Privacy | Terms of Use | Mobile
Web03 | 2.8.1411022.1 | Last Updated 5 Jul 2007
Article Copyright 2007 by Hitesh Sharma
Everything else Copyright © CodeProject, 1999-2014
Layout: fixed | fluid