Async socks in a separate thread

MuZZy,

-- FYI Managed Threading Best Practices does not recommend using Abort to
terminate a thread. Check item #1 in "General Recommendations " at this link:

http://msdn.microsoft.com/library/de...tpractices.asp

It's better to use your own event and/or boolean flag to signal that a
thread should stop processing.

-- I found the async socket documentation to be horrible... I burned up an
MSDN helpdesk call and got the following advice:

1) Do NOT try to use the manual wait handle returned with some async socket
APIs; it is not predictable. Declare and use your own events instead.

2) Your main listening loop should open the listener socket, issue
BeginAccept(), and then sleep until a connect attempt arrives or until the
program is stopped {this implies that you'll be waiting on 2 events}. When a
connection has been accepted by the callback handler loop around and issue
BeginAccept again.

Assuming that you have declared an event to signal program stop and an event
to signal an accepted connection, psuedo code for main listening loop looks
like this:

using (Socket listener = new Socket(...))
{
listener.Bind(. ..);
listener.Listen (...);

bool running = true;
while (running)
{
acceptEvent.Res et();
listener.BeginA ccept(new AsyncCallback(A cceptCallback), listener);
switch (WaitHandle.Wai tAny(acceptEven t, stopEvent))
{
case 0:
// acceptEvent - client connected, loop around again
break;
default:
// stopEvent or wait error - fall out of loop
running = false;
break;
}
}
}

3) When a client attempts to connect the accept callback handler should
issue EndAccept, signal the main thread that it has accepted a connection,
and then hand the accepted client off to another thread. The accept handler
MUST NOT process the client socket, it must EndAccept and return ASAP.

Assuming the "acceptEven t" from above, here is a working callback handler
that accepts a client connection, queues the client to the thread pool for
further processing, then signals the main loop that a client has been
accepted:

void AcceptCallback( IAsyncResult ar)
{
try
{
Socket socket = ((Socket)ar.Asy ncState).EndAcc ept(ar);
ThreadPool.Queu eUserWorkItem(n ew WaitCallback(So cketMain), socket);
}
catch (Exception ex)
{
trace.Exception (ex);
}
finally
{
acceptEvent.Set ();
}
}

4) The ThreadPool handler "SocketMain " receives a connected socket and it
can do whatever it wishes to do with the client:

void SocketMain(obje ct o)
{
using (Socket socket = (Socket)o)
{
... Do whatever ...
}
}

--Richard

"MuZZy" wrote:

Hi,

Could someone pls help me here:

If i use async sockets in the separate thread like this:

void ThreadFunction( )
{
.....
1. MySocket.BeginA ccept(AsyncCall Back(OnConnectR equest), MySocket);
2. ??????????
}

What do i do after line 1?
Do i put an endless loop in order to keep the thread alive?
And where do i put try{} catch{} to catch ThreadAbortExce ption thrown into the thread when i call Abort on the thread?

Thank you,
Andrey

Sample snippet:
AsyncCallback OnConnectReques t;

void OnConnectReques t(IAsyncResult ar)
{

// you have a connection, now start to receive---
try
{
Socket s = ar.AsyncState as Socket;
Socket s2 = s.EndAccept(ar) ;
// Keep the "Accept" process in motion
s.BeginAccept(a cceptCallback, s);
// Create a state object for client
StateObject state = new StateObject();
state.WorkerSoc ket = s2;
// Start an async receive
state.WorkerSoc ket.BeginReceiv e(state.Bytes, 0,
state.Bytes.Len gth, 0, receiveCallback , state);
}
catch(SocketExc eption e)
{
Debug.WriteLine (e.Message);
Console.WriteLi ne( "SocketExceptio n:"+ e.Message);
}
return; // Return the thread to the pool
}

Note that BeginAccept is called from within the callback method.

There are lots of different ways to do this, and it can be pretty confusing.
Some pretty good sample code to get you started at MSDN online.
Just look up "Asynchrono us sockets".
--Peter

"MuZZy" <le*******@yaho o.com> wrote in message
news:JP******** ************@rc n.net...

Hi,

Could someone pls help me here:

If i use async sockets in the separate thread like this:

void ThreadFunction( )
{
.....
1. MySocket.BeginA ccept(AsyncCall Back(OnConnectR equest), MySocket);
2. ??????????
}

What do i do after line 1?
Do i put an endless loop in order to keep the thread alive?
And where do i put try{} catch{} to catch ThreadAbortExce ption thrown into
the thread when i call Abort on the thread?

Thank you,
Andrey

Peter Bromberg [C# MVP] wrote:

Sample snippet:
AsyncCallback OnConnectReques t;

void OnConnectReques t(IAsyncResult ar)
{

// you have a connection, now start to receive---
try
{
Socket s = ar.AsyncState as Socket;
Socket s2 = s.EndAccept(ar) ;
// Keep the "Accept" process in motion
s.BeginAccept(a cceptCallback, s);
// Create a state object for client
StateObject state = new StateObject();
state.WorkerSoc ket = s2;
// Start an async receive
state.WorkerSoc ket.BeginReceiv e(state.Bytes, 0,
state.Bytes.Len gth, 0, receiveCallback , state);
}
catch(SocketExc eption e)
{
Debug.WriteLine (e.Message);
Console.WriteLi ne( "SocketExceptio n:"+ e.Message);
}
return; // Return the thread to the pool
}

Note that BeginAccept is called from within the callback method.

There are lots of different ways to do this, and it can be pretty confusing.
Some pretty good sample code to get you started at MSDN online.
Just look up "Asynchrono us sockets".
--Peter
Thank you for the reply!
But thing is that i already have what you mentioned above,
i just need to know how to keep the thread function from returning
after i've initiated BeginAccept(... ).

Thank you,
Andrey


"MuZZy" <le*******@yaho o.com> wrote in message
news:JP******** ************@rc n.net...

Hi,

Could someone pls help me here:

If i use async sockets in the separate thread like this:

void ThreadFunction( )
{
.....
1. MySocket.BeginA ccept(AsyncCall Back(OnConnectR equest), MySocket);
2. ??????????
}

What do i do after line 1?
Do i put an endless loop in order to keep the thread alive?
And where do i put try{} catch{} to catch ThreadAbortExce ption thrown into
the thread when i call Abort on the thread?

Thank you,
Andrey

Or spawn a listener thread and let that block.

Peter Wone wrote:

Or spawn a listener thread and let that block.

What do you mean here?

>> Or spawn a listener thread and let that block.

What do you mean here?

Never mind blocking. This is how you do it.

This code is excerpted from a custom control I wrote for an embedded
webserver. I use it to fulfil requests for addition resources like CSS or
images when I use an embedded webserver to render HTML. You can make it pick
a random port, and the widget exposes a LocalBaseUrl property that tells
your app the base URL for connecting to itself. That's what baseURL is
about.

Sockets aren't that hard but it takes a mind that's twisted in a special
way.

THIS CODE IS COPYRIGHT TO ME AND ANYONE PLANNING ON USING IT IN A
COMMERCIAL APPLICATION CAN JOLLY WELL PUBLICLY CREDIT ME.

The next Indian contractor to send a peremptory "UGENT: PLS HELP" message to
my private email address will receive pictures of dead cows in his work
inbox unless the request is accompanied by an offer to pay for my time and
trouble.
....
private TcpListener tcpListener;
private bool useRandomPort = true;
private int tcpListenerPort = 8080;
private bool shouldListen = false;
private Thread ListenerThread;
private string baseURL;

....
public void Start() {
if (useRandomPort)
tcpListenerPort = (new Random()).Next( 16384,65535);
baseURL = "http://localhost:" + tcpListenerPort + "/";
tcpListener = new TcpListener(IPA ddress.Loopback ,tcpListenerPor t);
if ((VirtualRoots. Count>0) && (null==filesys) )
filesys = new WebResourceProv iderFileSystem( );
shouldListen = true;
tcpListener.Sta rt();
ListenerThread = new Thread(new ThreadStart(Lis ten));
ListenerThread. Priority = ThreadPriority. BelowNormal;
ListenerThread. Name = string.Format(" {0} HTTP
Listener",this. GetType().ToStr ing());
ListenerThread. Start();
}
public void Stop() {
shouldListen = false;
}
....
private void Listen(){
while (shouldListen) {
if (tcpListener.Pe nding()){
Socket socket = tcpListener.Acc eptSocket();
socket.Blocking = false;
//Some applications disconnect immediately when just checking
//the continued presence of this app. These produce SelectError.
if (!socket.Poll(5 000,SelectMode. SelectError)) {
//spawn another thread to handle this request
HttpRequestHand ler handler = new
HttpRequestHand ler(this,socket );
Thread newThread = new Thread(new ThreadStart(han dler.Exec));
newThread.Name = string.Format(" {0} request
handler",this.G etType().ToStri ng());
newThread.Start ();
}
} else
Thread.Sleep(20 0);
}
}

> The next Indian contractor to send a peremptory "UGENT: PLS HELP" message

to my private email address will receive pictures of dead cows in his work

That comment was in poor taste. I hope you realize that.

--
Regards,
Alvin Bruney

[Shameless Author plug]
The Microsoft Office Web Components Black Book with .NET
Now Available @ http://tinyurl.com/27cok
----------------------------------------------------------
"Peter Wone" <pe****@wamoz.c om> wrote in message
news:Ox******** ******@TK2MSFTN GP15.phx.gbl...

Or spawn a listener thread and let that block.

What do you mean here?

Never mind blocking. This is how you do it.

This code is excerpted from a custom control I wrote for an embedded
webserver. I use it to fulfil requests for addition resources like CSS or
images when I use an embedded webserver to render HTML. You can make it
pick a random port, and the widget exposes a LocalBaseUrl property that
tells your app the base URL for connecting to itself. That's what baseURL
is about.

Sockets aren't that hard but it takes a mind that's twisted in a special
way.

THIS CODE IS COPYRIGHT TO ME AND ANYONE PLANNING ON USING IT IN A
COMMERCIAL APPLICATION CAN JOLLY WELL PUBLICLY CREDIT ME.

The next Indian contractor to send a peremptory "UGENT: PLS HELP" message
to my private email address will receive pictures of dead cows in his work
inbox unless the request is accompanied by an offer to pay for my time and
trouble.
...
private TcpListener tcpListener;
private bool useRandomPort = true;
private int tcpListenerPort = 8080;
private bool shouldListen = false;
private Thread ListenerThread;
private string baseURL;

...
public void Start() {
if (useRandomPort)
tcpListenerPort = (new Random()).Next( 16384,65535);
baseURL = "http://localhost:" + tcpListenerPort + "/";
tcpListener = new TcpListener(IPA ddress.Loopback ,tcpListenerPor t);
if ((VirtualRoots. Count>0) && (null==filesys) )
filesys = new WebResourceProv iderFileSystem( );
shouldListen = true;
tcpListener.Sta rt();
ListenerThread = new Thread(new ThreadStart(Lis ten));
ListenerThread. Priority = ThreadPriority. BelowNormal;
ListenerThread. Name = string.Format(" {0} HTTP
Listener",this. GetType().ToStr ing());
ListenerThread. Start();
}
public void Stop() {
shouldListen = false;
}
...
private void Listen(){
while (shouldListen) {
if (tcpListener.Pe nding()){
Socket socket = tcpListener.Acc eptSocket();
socket.Blocking = false;
//Some applications disconnect immediately when just checking
//the continued presence of this app. These produce SelectError.
if (!socket.Poll(5 000,SelectMode. SelectError)) {
//spawn another thread to handle this request
HttpRequestHand ler handler = new
HttpRequestHand ler(this,socket );
Thread newThread = new Thread(new ThreadStart(han dler.Exec));
newThread.Name = string.Format(" {0} request
handler",this.G etType().ToStri ng());
newThread.Start ();
}
} else
Thread.Sleep(20 0);
}
}

So are the peremptory demands to do unpaid work that they get paid for.

"Alvin Bruney [MVP]" <vapor at steaming post office> wrote in message
news:Ot******** ******@TK2MSFTN GP15.phx.gbl...

The next Indian contractor to send a peremptory "UGENT: PLS HELP" message
to my private email address will receive pictures of dead cows in his
work

That comment was in poor taste. I hope you realize that.

--
Regards,
Alvin Bruney

[Shameless Author plug]
The Microsoft Office Web Components Black Book with .NET
Now Available @ http://tinyurl.com/27cok
----------------------------------------------------------
"Peter Wone" <pe****@wamoz.c om> wrote in message
news:Ox******** ******@TK2MSFTN GP15.phx.gbl...

Or spawn a listener thread and let that block.

What do you mean here?

Never mind blocking. This is how you do it.

This code is excerpted from a custom control I wrote for an embedded
webserver. I use it to fulfil requests for addition resources like CSS or
images when I use an embedded webserver to render HTML. You can make it
pick a random port, and the widget exposes a LocalBaseUrl property that
tells your app the base URL for connecting to itself. That's what baseURL
is about.

Sockets aren't that hard but it takes a mind that's twisted in a special
way.

THIS CODE IS COPYRIGHT TO ME AND ANYONE PLANNING ON USING IT IN A
COMMERCIAL APPLICATION CAN JOLLY WELL PUBLICLY CREDIT ME.

The next Indian contractor to send a peremptory "UGENT: PLS HELP" message
to my private email address will receive pictures of dead cows in his
work inbox unless the request is accompanied by an offer to pay for my
time and trouble.
...
private TcpListener tcpListener;
private bool useRandomPort = true;
private int tcpListenerPort = 8080;
private bool shouldListen = false;
private Thread ListenerThread;
private string baseURL;

...
public void Start() {
if (useRandomPort)
tcpListenerPort = (new Random()).Next( 16384,65535);
baseURL = "http://localhost:" + tcpListenerPort + "/";
tcpListener = new TcpListener(IPA ddress.Loopback ,tcpListenerPor t);
if ((VirtualRoots. Count>0) && (null==filesys) )
filesys = new WebResourceProv iderFileSystem( );
shouldListen = true;
tcpListener.Sta rt();
ListenerThread = new Thread(new ThreadStart(Lis ten));
ListenerThread. Priority = ThreadPriority. BelowNormal;
ListenerThread. Name = string.Format(" {0} HTTP
Listener",this. GetType().ToStr ing());
ListenerThread. Start();
}
public void Stop() {
shouldListen = false;
}
...
private void Listen(){
while (shouldListen) {
if (tcpListener.Pe nding()){
Socket socket = tcpListener.Acc eptSocket();
socket.Blocking = false;
//Some applications disconnect immediately when just checking
//the continued presence of this app. These produce SelectError.
if (!socket.Poll(5 000,SelectMode. SelectError)) {
//spawn another thread to handle this request
HttpRequestHand ler handler = new
HttpRequestHand ler(this,socket );
Thread newThread = new Thread(new ThreadStart(han dler.Exec));
newThread.Name = string.Format(" {0} request
handler",this.G etType().ToStri ng());
newThread.Start ();
}
} else
Thread.Sleep(20 0);
}
}