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A Voice Chat Application in C#

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5 Jul 2007CPOL2 min read 713.7K   42.9K   248   155
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

Introduction

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:

C#
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:

C#
//Using UDP sockets
clientSocket = new Socket(AddressFamily.InterNetwork, 
    SocketType.Dgram, 
    ProtocolType.Udp);
EndPoint ourEP = new IPEndPoint(IPAddress.Any, 1450);

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

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

//Receive data asynchornously.
clientSocket.BeginReceiveFrom(byteData,
    0, byteData.Length,
    SocketFlags.None,
    ref remoteEP,
    new AsyncCallback(OnReceive),
    null);

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:

C#
private void InitializeCall()
{
    try
    {
        //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.
        receiverThread.Start();
        senderThread.Start();
        btnCall.Enabled = false;
        btnEndCall.Enabled = true;
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message, 
            "VoiceChat-InitializeCall ()", MessageBoxButtons.OK, 
        MessageBoxIcon.Error);
    }
}

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

References

History

  • 5 July, 2007 -- Original version posted

License

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


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Comments and Discussions

 
GeneralMy vote of 5 Pin
Member 446500731-Mar-11 14:29
Member 446500731-Mar-11 14:29 
GeneralHi Pin
Kiya161-Mar-11 7:33
Kiya161-Mar-11 7:33 
Generali want to make it over internet Pin
crysis8928-Feb-11 11:28
crysis8928-Feb-11 11:28 
Generalerror Pin
samathu22-Feb-11 20:11
samathu22-Feb-11 20:11 
Generalerror Pin
samathu21-Feb-11 4:19
samathu21-Feb-11 4:19 
GeneralSome question Pin
Mohammad Reza Valadkhani19-Jan-11 2:27
professionalMohammad Reza Valadkhani19-Jan-11 2:27 
GeneralMy vote of 3 Pin
lxxlxx4-Jan-11 2:09
lxxlxx4-Jan-11 2:09 
GeneralMuLawEncoder Vs ALawEncoder What's the difference Pin
jibin.mn30-Oct-10 0:09
jibin.mn30-Oct-10 0:09 
Hi,
a very good article on every aspect and code is 100% error free...
I had some doubt..??
1. What is the difference between 2 Encryptions technique MuLawEncoder and ALawEncode..I found nearly 50% compression for both..
2.What is the advantage of UdpClient over Socket
Pls reply


Thanks.
Generalerrors regarding the project "A Voice Chat Application in C#". Pin
hemendrapsingh28-Feb-10 9:17
hemendrapsingh28-Feb-10 9:17 
GeneralMy vote of 2 Pin
somireddy25-Feb-10 22:04
somireddy25-Feb-10 22:04 
GeneralCompact Framework Pin
sonia108211-Jan-10 19:20
sonia108211-Jan-10 19:20 
QuestionError while calling on second time [modified] Pin
hiran53612-Oct-09 21:08
hiran53612-Oct-09 21:08 
Generalnot working in studio 2008 Pin
surpatel785-Oct-09 2:21
surpatel785-Oct-09 2:21 
AnswerRe: not working in studio 2008 Pin
Smacky31125-May-10 3:44
Smacky31125-May-10 3:44 
GeneralNotify Pin
mayuwi1-Oct-09 15:12
mayuwi1-Oct-09 15:12 
QuestionHow to select the device dynamically ? Pin
Jack98739-Sep-09 0:23
Jack98739-Sep-09 0:23 
AnswerRe: How to select the device dynamically ? Pin
mayuwi1-Oct-09 13:52
mayuwi1-Oct-09 13:52 
GeneralVoiveChat-InitializeCall() Only one usage of each socket address (protocol/ network address/ port) is nomally permitted Pin
aadiost24-Aug-09 2:49
aadiost24-Aug-09 2:49 
GeneralRe: VoiveChat-InitializeCall() Only one usage of each socket address (protocol/ network address/ port) is nomally permitted Pin
sloaken6-Sep-09 21:18
sloaken6-Sep-09 21:18 
GeneralOnly one usage of each socket address(protocol/network address/port) is normally permitted Pin
goitom219-Aug-09 4:36
goitom219-Aug-09 4:36 
GeneralRe: Only one usage of each socket address(protocol/network address/port) is normally permitted [modified] Pin
sloaken6-Sep-09 9:49
sloaken6-Sep-09 9:49 
GeneralRe: Only one usage of each socket address(protocol/network address/port) is normally permitted Pin
surpatel785-Oct-09 2:48
surpatel785-Oct-09 2:48 
QuestionCan this project be ported for Compact Framework? Pin
m_mughalz18-Aug-09 19:55
m_mughalz18-Aug-09 19:55 
AnswerRe: Can this project be ported for Compact Framework? Pin
jerome51366-Jan-10 10:58
jerome51366-Jan-10 10:58 
QuestionHave you implement on silent detection? Pin
Roathvb2-Aug-09 7:52
Roathvb2-Aug-09 7:52 

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