C# Discussion Boards - CodeProject

4-Oct-09 22:55

Its about Tcp/Ip and threading
Here i am modifing some others work and have very little clue about both tcp & threading.

The application is about sending and recv data thru tcp
On Intialize() method :

try
{
	Thread trStartListening = new Thread(new ThreadStart(ListenThread));
	trStartListening.Name = "Thread_tcp_Listen_" + addTcp.PortNo.ToString();
	trStartListening.IsBackground = true;
	trStartListening.Start();
}
catch(Exception e)
{
	OnSocketError(e.Message);
}

In ListenThread() method:

IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Any, addTcp.PortNo);
// Establish the local endpoint for the socket.
TcpListener server = new TcpListener(localEndPoint);
try
{
	server.Start();
	while (!ShuttingDown)
	{		
		TcpClient client = server.AcceptTcpClient();
		// Buffer for reading data
		byte[] bytes = new Byte[256];
		string data = null;
		// Get a stream object for reading and writing
		NetworkStream stream = client.GetStream();
		lock(this)
		{
			int i;
			// Loop to receive all the data sent by the client.
			while((i = stream.Read(bytes, 0, bytes.Length))!=0) 
			{   
				....//relative code
			}
		}
	}

	server.Stop();
}
catch (Exception e)
{
	OnSocketError(e.Message);
}

On Send method

try 
{
	curXmt = TransmittDir;
 	string Conn = CDS.GetConnectionString(curXmt);
	int port = 13000;
	string Ip = "";
	ParseConnectionString(Conn,ref Ip,ref port);
	Sendingip = Conn;
	TcpClient client = new TcpClient(Ip, port);
	
	string Message = CDS.GetMessage();
	byte[] data = System.Text.Encoding.ASCII.GetBytes(Message);         
	// Get a client stream for reading and writing.	
	NetworkStream stream = client.GetStream();
	
	// Send the message to the connected TcpServer. 
	stream.Write(data, 0, data.Length);
	
	// Close everything.
	client.Close();         
} 
catch (ArgumentNullException e) 
{
	.....	
} 
catch (SocketException e) 
{
	.....
}

And On UnIntialize()

public void UnIntialize()
{
	ShuttingDown = true;
}

Application working fine if condition are ideal, but when i call UnIntialize(), recv and sending stop.

Then i have to restart the whole application again for proper working.

A few question i have

a) Do i have to abort the thread in UnIntialize()?
b) If a thread started does it calls itself without any explicit calling?
Or we have to call/create it again?
c) What is life of a thread(if we set IsBackGround = true, then it aborted by OS). But what if we dont mention it.
d) When we starts Tcp/Ip listner, how long it listens. any life period?

N a v a n e e t h5-Oct-09 0:14

5-Oct-09 0:14

Hum Dum wrote:
Do i have to abort the thread in UnIntialize()?

Nope. Aborting a thread forcefully using Thread.Abort is a bad practice. When you set ShuttingDown = true, the thread will exit safely.

Hum Dum wrote:
If a thread started does it calls itself without any explicit calling?

You need to explain what you meant here.

Hum Dum wrote:
What is life of a thread(if we set IsBackGround = true, then it aborted by OS). But what if we dont mention it.

When IsBackground is true, it ends when the parent thread ends. An active foreground thread can make the application alive and it can run to anytime.

Hum Dum wrote:
When we starts Tcp/Ip listner, how long it listens. any life period?

It listens until you stops it or timeout value reached.

Hum Dum wrote:

try
{
Thread trStartListening = new Thread(new ThreadStart(ListenThread));
trStartListening.Name = "Thread_tcp_Listen_" + addTcp.PortNo.ToString();
trStartListening.IsBackground = true;
trStartListening.Start();
}
catch(Exception e)
{
OnSocketError(e.Message);
}

The try/catch is pointless here. Exceptions thrown from a thread won't be caught here. It will be handled by the exception handler provided in the thread's executing method.

Hum Dum wrote:
Then i have to restart the whole application again for proper working.

Once thread stops, it will stop sending and receiving. You need to start the thread again if you need to continue listening.

Your code has lot of flaws and I'd suggest to take a book on networking in C# before you do serious network programming.

Navaneeth

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Hum Dum5-Oct-09 0:39

5-Oct-09 0:39

N a v a n e e t h wrote:
Hum Dum wrote:
If a thread started does it calls itself without any explicit calling?

You need to explain what you meant here.

With reference to my previous post,
we setting ShuttingDown = true in UnIntialize() method?
program checking its value in ListenThread(), and it is on the thread i started. So, when will this ListenThread() get called next time?

It get called automatically?

Here problem i am facing is, if i call UnIntialize() and then call Intialize(One in which i am starting the thread) the app. not working.

I call them on Start, Stop button on form.
I have to exit main application, then only it works.

any help?

regards

N a v a n e e t h5-Oct-09 0:46

5-Oct-09 0:46

You are not resetting the ShuttingDown variable's value. On initialize method, add

ShuttingDown = false;
// other code

Navaneeth

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Hum Dum5-Oct-09 0:55

5-Oct-09 0:55

thanks for replay.

but what about my question?
When we assign a task to thread does it completes it and stops there.
and we have to call it again for same work.

And if yes?
then creating same thread again and again (if we are using that work frequently) going to create any overhead?

Do you spot me to any link for threading or refer me a book on networking and threading.

regards

N a v a n e e t h5-Oct-09 1:08

5-Oct-09 1:08

Hum Dum wrote:
When we assign a task to thread does it completes it and stops there.

It executes the method and returns. When method execution is done, thread ends.

Hum Dum wrote:
then creating same thread again and again (if we are using that work frequently) going to create any overhead?

You are not using the same thread. Each time a new thread will be created. There is an overhead associated with creating threads. It is negligible for small number of threads.

Hum Dum wrote:
Do you spot me to any link for threading or refer me a book on networking and threading.

Here is one for threading[^]. Here[^] is one MSDN article on network programming.

Navaneeth

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Hum Dum5-Oct-09 2:34

5-Oct-09 2:34

I debugged the application, when i press start button i.e calling Initialize()(after stopping thru stop), it jumps to ListenThread() method,

when server.Start(); //this lines comes, it exit thread by saying code with 0

but if i use server.Stop() in UnInitialize(), then its working fine.

Now, other problem is, what if server is already stopped, how can i check TcpListner state. (for server variable plz see original post, In ListenThread() method)

regards.

N a v a n e e t h5-Oct-09 15:47