How can I use sockets without callbacks?
Cash GEDNY -- ccoyne@equityny.ml.com
Thursday, March 27, 1997
Environment: NT 3.51 Visual C++ 4.0
In using sockets, I want to be able to have a DLL that handles socket
communications for my apps. One of the things I want this DLL to be able
to do is to have a send method that the app calls and then the send method
would return the results of my socket send (i.e. from the Receive), so that
the app does not have to provide a callback function. Everything I've
tried so far just seems to hang up the system (using regular callbacks,
response time is instantaneous).
Does anyone have any suggestions about how to go about this or can point me
in the right direction?
TIA,
C Coyne
ccoyne@gedny.ml.com
Paul Gerhart -- pgerhart@voicenet.com
Friday, March 28, 1997
[Mini-digest: 2 responses]
Coyne, Cash ( GEDNY) wrote:
>
> Environment: NT 3.51 Visual C++ 4.0
>
> In using sockets,
I have two sample sockets, MFC 4.0, VC++ 4.0, Win95 programs that are
Freeware. They live at
http://www.voicenet.com/~pgerhart/_shware.html
Neither uses a hand-crafted DLL - you make no claim as to why that is of
benefit. Also, neither uses CSocket. Both are tutorials that I wrote for
my own benefit.
The first example is called SockTest and it is at
http://www.voicenet.com/~pgerhart/socktst2.zip
It features a CWnd derived class wrapper around the sockets API. Donald
C. Asonye wrote that class as freeware. SockTest is a client that lets
you ping, get HTML source etc. from a server.
The second example is called MiniFTP and it is at
http://www.voicenet.com/~pgerhart/miniftp1.zip
It uses the API directly (not Donald's class wrapper) in the
Asynchronous fashion (i.e. driven by the Windows message pump). It is an
actual FTP client done as a tutorial. Don't expect to tolerate every
wacky condition imaginable but it will let you up/down load ASCII or
binary files.
Both are simple CView apps - while they are 32 bit, no Win32 common
controls are used.
If you want to stay a 4.0 then these may be of help.
Hope this helps.
I want to be able to have a DLL that handles socket
> communications for my apps. One of the things I want this DLL to be able
> to do is to have a send method that the app calls and then the send method
> would return the results of my socket send (i.e. from the Receive), so that
> the app does not have to provide a callback function. Everything I've
> tried so far just seems to hang up the system (using regular callbacks,
> response time is instantaneous).
>
> Does anyone have any suggestions about how to go about this or can point me
> in the right direction?
>
> TIA,
>
> C Coyne
> ccoyne@gedny.ml.com
--
#########################
# Paul Gerhart #
# pgerhart@voicenet.com #
#########################
-----From: Dean Grimm
Use select() instead of WSAAsyncSelect() to check when data is ready at the socket.
I use the following code to check for data on my non-blocking socket (m_s is the
socket descriptor)
void CBsdStreamSocket::WaitForRecvReady()
{
fd_set rfds;
int nResponse;
struct timeval tv = {0,0};
do
{
FD_ZERO(&rfds);
FD_SET(m_s, &rfds);
if((nResponse = select(m_s+1,&rfds, 0,0,&tv)) == SOCKET_ERROR)
{
ErrorLog("CBsdStreamSocket::WaitForRecvReady: Select Error");
}
}
while(!(nResponse !=0 && FD_ISSET(m_s,&rfds)));
}
Hope this helps.
Dean Grimm
Software Engineer / Cortron Corp.
----------
From: Coyne, Cash ( GEDNY)
Sent: Thursday, March 27, 1997 5:13 AM
To: 'mfc-l@netcom.com'
Subject: How can I use sockets without callbacks?
Environment: NT 3.51 Visual C++ 4.0
In using sockets, I want to be able to have a DLL that handles socket
communications for my apps. One of the things I want this DLL to be able
to do is to have a send method that the app calls and then the send method
would return the results of my socket send (i.e. from the Receive), so that
the app does not have to provide a callback function. Everything I've
tried so far just seems to hang up the system (using regular callbacks,
response time is instantaneous).
Does anyone have any suggestions about how to go about this or can point me
in the right direction?
TIA,
C Coyne
ccoyne@gedny.ml.com
John Moulder -- jm@wg.icl.co.uk
Tuesday, April 01, 1997
Take a look at WSAAsyncSelect(). This allows you to register a user defined
message (WM_USER + xxx) that is sent to your window's message handler when
a specific socket event, or events occur.
The trick is to set some flags in your window's message handler according
to each socket notification, and check these flags in a message loop within
your DLL's send/receive function.
The example below is in C pseudo code.
switch (message)
{
case WM_SOCKET_NOTIFY :
{
switch (WSAGETSELECTEVENT(lParam))
{
case FD_READ : bCanRead = TRUE; break;
case FD_WRITE : bCanWrite = TRUE;
case FD_CONNECT : bConnecting = FALSE;
default : ...
}
}
}
When reading and writing, you need to await the appropriate socket
notification before calling recv() or send().
bCanWrite = FALSE;
if (SOCKET_ERROR != WSAAsyncSelect(sd, hwnd, WM_SOCKET_NOTIFY, FD_READ |
FD_CLOSE))
{
/*
* MESSAGE LOOP
*
* await the asynchronous notification message
* and allow other applications to run.
*/
while (GetMessage(&msg, NULL, 0, 0))
{
/* handle the message normally */
TranslateMessage(&msg);
/* Send it to our window */
DispatchMessage(&msg);
if (bCanWrite)
{
/* cancel the asynchronous select */
WSAAsyncSelect(_sd, _hwnd, 0, 0);
break;
}
} /* while */
// now do the send()
send(...);
}
Repeat the above with FD_READ notifications to do the recv().
Of course, the error management is omitted from this example for clarity!
And if your code is in a DLL, your should consider if you will have
multiple, concurrent calling applications, and so require the state
information (bCanWrite etc) per task or per socket connection. You may be
able to get some advantage from C++ and MFC's classes; I don't know as I
did it in raw C and WinSock calls.
----------
> From: Coyne, Cash ( GEDNY)
> To: 'mfc-l@netcom.com'
> Subject: How can I use sockets without callbacks?
> Date: 27 March 1997 14:13
>
> Environment: NT 3.51 Visual C++ 4.0
>
> In using sockets, I want to be able to have a DLL that handles socket
> communications for my apps. One of the things I want this DLL to be able
> to do is to have a send method that the app calls and then the send
method
> would return the results of my socket send (i.e. from the Receive), so
that
> the app does not have to provide a callback function. Everything I've
> tried so far just seems to hang up the system (using regular callbacks,
> response time is instantaneous).
>
> Does anyone have any suggestions about how to go about this or can point
me
> in the right direction?
>
> TIA,
>
> C Coyne
> ccoyne@gedny.ml.com
>
>
>
Andrew L. Snow -- als@fl.net.au
Wednesday, April 02, 1997
[Mini-digest: 2 responses]
> From: Coyne, Cash ( GEDNY)
> Subject: How can I use sockets without callbacks?
> Date: 27 March 1997 14:13
> Environment: NT 3.51 Visual C++ 4.0
> In using sockets, I want to be able to have a DLL that handles socket
> communications for my apps. One of the things I want this DLL to be able
> to do is to have a send method that the app calls and then the send method
> would return the results of my socket send (i.e. from the Receive), so that
> the app does not have to provide a callback function. Everything I've
> tried so far just seems to hang up the system (using regular callbacks,
> response time is instantaneous).
Once again, the Visual C++ online help :-)
If using MFC is OK (you don't specifically state it isn't) then check out
CSocket. It makes your life easier by blocking (ie. the calls to
read/write/connect don't return unless something has actually happened).
So what I have done is start a thread which will handle all your
communications,
then:
CSocket mysocket;
mysocket.Create();
mysocket.Connect(address, port); // address can be name or IP number
The last function returns 0 if theres an error.
After it has connected, you can either use mysocket.Send() and
mysocket.Receive()
or use a CSocketFile to trick yourself into thinking its a file you're
reading/writing to, not a socket.
But for send ::Send() and ::Receive(), the examples are:
char buf[]="Hmmm... ";
mysocket.Send(buf, strlen(buf) );
the call returns 0 or SOCKET_ERROR if there's a problem.
and to receive 128 bytes,
char buf[128];
mysocket.Receive(buf, 128);
the call returns the number of bytes read, SOCKET_ERROR if there's an error,
or zero if the other end closed.
Again, see the online help for details. The help says that if you use CSocket,
your messages are still pumped so in theory you don't have to create a thread.
In practice a thread may be a better idea, so your interface is more
responsive.
The "Windows Sockets: Sequence of operations" article is particularly useful.
-----From: "Jay F."
Or you may just want to consider using threads and turn off
notifications.
Just make sure your socket is blocking.
With threads there is no reason to worry about using AsyncSelect calls,
or using a notification when messages come in.
When a message arrives, the socket unblocks, you read it , stick it on
a queue, and block again.
--
Jay Ferguson (Because the Best Things in The Net are FREE)
http://www.cse.psu.edu/~ferguson
jhf@hrb.com
John Moulder wrote:
Take a look at WSAAsyncSelect(). This allows you to register a user
defined
message (WM_USER + xxx) that is sent to your window's message
handler when
a specific socket event, or events occur.
The trick is to set some flags in your window's message handler
according
to each socket notification, and check these flags in a message loop
within
your DLL's send/receive function.
The example below is in C pseudo code.
switch (message)
{
case WM_SOCKET_NOTIFY :
{
switch (WSAGETSELECTEVENT(lParam))
{
case FD_READ : bCanRead = TRUE; break;
case FD_WRITE : bCanWrite = TRUE;
case FD_CONNECT : bConnecting = FALSE;
default : ...
}
}
}
When reading and writing, you need to await the appropriate socket
notification before calling recv() or send().
bCanWrite = FALSE;
if (SOCKET_ERROR != WSAAsyncSelect(sd, hwnd, WM_SOCKET_NOTIFY,
FD_READ |
FD_CLOSE))
{
/*
* MESSAGE LOOP
*
* await the asynchronous notification message
* and allow other applications to run.
*/
while (GetMessage(&msg, NULL, 0, 0))
{
/* handle the message normally */
TranslateMessage(&msg);
/* Send it to our window */
DispatchMessage(&msg);
if (bCanWrite)
{
/* cancel the asynchronous select */
WSAAsyncSelect(_sd, _hwnd, 0, 0);
break;
}
} /* while */
// now do the send()
send(...);
}
Repeat the above with FD_READ notifications to do the recv().
Of course, the error management is omitted from this example for
clarity!
And if your code is in a DLL, your should consider if you will have
multiple, concurrent calling applications, and so require the state
information (bCanWrite etc) per task or per socket connection. You
may be
able to get some advantage from C++ and MFC's classes; I don't know
as I
did it in raw C and WinSock calls.
----------
> From: Coyne, Cash ( GEDNY)
> To: 'mfc-l@netcom.com'
> Subject: How can I use sockets without callbacks?
> Date: 27 March 1997 14:13
>
> Environment: NT 3.51 Visual C++ 4.0
>
> In using sockets, I want to be able to have a DLL that handles
socket
> communications for my apps. One of the things I want this DLL to
be able
> to do is to have a send method that the app calls and then the
send
method
> would return the results of my socket send (i.e. from the
Receive), so
that
> the app does not have to provide a callback function. Everything
I've
> tried so far just seems to hang up the system (using regular
callbacks,
> response time is instantaneous).
>
> Does anyone have any suggestions about how to go about this or can
point
me
> in the right direction?
>
> TIA,
>
> C Coyne
> ccoyne@gedny.ml.com
>
>
>
Become an MFC-L member
| Вернуться в корень Архива
|