C / C++ / MFC

5-Sep-07 23:01

I would like my UDP server to send the data when the client connects; say at a rate of 100 msec.
But I can only get it working when the Server does a receive first (so the client has to do a send) then the Server does the send.

Can this be done? The server fails if I do not do the Receive and the client fails if I dont run the server first.

See code below:-

	while(g_bUDP_Socket_Created && g_bUDPStatus)<br />
	{<br />
		bytesRead = recvfrom (conn_socket, (char *)&RxBuffer, sizeof(RxBuffer), 0, (struct sockaddr *)&from, &length);<br />
		// bytesRead = recv(conn_socket, BufferIn, sizeof(BufferIn), 0);<br />
		// Check for error and terminate the thread if any found<br />
		if (bytesRead == SOCKET_ERROR) <br />
		{<br />
			g_szFormatting.Format("Couldn't receive data, %d",WSAGetLastError());<br />
			::MessageBox((HWND)NULL,g_szFormatting, NULL,MB_ICONEXCLAMATION );<br />
			closesocket (conn_socket);<br />
			WSACleanup();<br />
			return -1;<br />
		}<br />
<br />
		retval = sendto (conn_socket, (char*)TxBuffer, sizeof(Tx_Data), 0, (struct sockaddr *)&from, fromlen);<br />
		if (retval == SOCKET_ERROR)<br />
		{	<br />
			g_szFormatting.Format("Couldn't send data, %d",WSAGetLastError());<br />
			::MessageBox((HWND)NULL,g_szFormatting, NULL,MB_ICONEXCLAMATION );<br />
			closesocket (conn_socket);<br />
			WSACleanup();<br />
		}<br />
	}

Mark Salsbery6-Sep-07 5:51

Mark Salsbery

6-Sep-07 5:51

Are you getting an error? If so, what is the error code returned by WSAGetLastError()?

Andy202 wrote:
say at a rate of 100 msec.

That isn't a rate, that's a duration.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Andy2026-Sep-07 10:58

6-Sep-07 10:58

If I comment out the receive I get error 10057 on the send.

All I want to do is transmit a UDP message at 10Hz. The client can be running or not. I will use port 5001, but I do not need to know the client PC.

The client will need to know both Port and PC - correct?

Andy.

Mark Salsbery6-Sep-07 11:33

Mark Salsbery

6-Sep-07 11:33

Andy202 wrote:
If I comment out the receive I get error 10057 on the send.

The error is WSAENOTCONN.
That's expected since you're using the "from" address from the recvfrom(),
which isn't going to be a valid address without a successful recvfrom() call.

Andy202 wrote:
I would like my UDP server to send the data when the client connects;

UDP is connectionless so you don't know if a client is connected or not.

It sounds like you need to either...

1) Keep track of clients that are listening - that would mean a client has to send a notification to
the server when it's ready to receive datagrams. The server can store a list of "connected" clients and
send the periodic datagrams to every address on the list.

2) Broadcast the periodic datagrams. Set the socket option SO_BROADCAST on the socket and send
to the broadcast address (INADDR_BROADCAST). The clients need to set the SO_BROADCAST socket option
as well.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Andy2027-Sep-07 4:48

7-Sep-07 4:48

Thanks again for your Post Mark, I now get Error = 10057 when the Client is not running and Error = 10093 when the Client is running.

// Setup port addresses<br />
local.sin_family = AF_INET;<br />
local.sin_addr.s_addr = INADDR_BROADCAST;<br />
local.sin_port = htons(port);<br />
<br />
conn_socket = socket(AF_INET, socket_type, 0); /* Open a socket */<br />
<br />
if (setsockopt (conn_socket, SOL_SOCKET, SO_BROADCAST, (char *) &TxBuffer, sizeof (TxBuffer)) == SOCKET_ERROR)<br />
{<br />
	closesocket (conn_socket);<br />
	g_szFormatting.Format("setsockopt() failed: %d\n",WSAGetLastError());<br />
	ReportMessages(g_szFormatting);<br />
	WSACleanup();<br />
	return false;<br />
}<br />
<br />
//Make it so you can attach more than one thing to a socket<br />
if (setsockopt (conn_socket, SOL_SOCKET, SO_REUSEADDR , (char *) &optval, sizeof(optval))  == SOCKET_ERROR)<br />
{				<br />
	g_szFormatting.Format("Couldn't set SO_REUSEADDR %d\n ", WSAGetLastError());<br />
	ReportMessages(g_szFormatting);<br />
	closesocket (conn_socket);<br />
	WSACleanup();<br />
	return false;<br />
}

And in the Writer Thread:-

while(g_bUDP_Socket_Created && g_bUDPStatus)<br />
{<br />
<br />
retval = sendto (conn_socket, (char*)TxBuffer, sizeof(Tx_Data), 0, NULL , 0);<br />
	if (retval == SOCKET_ERROR)<br />
	{	<br />
		g_szFormatting.Format("Couldn't send data, %d",WSAGetLastError());<br />
		::MessageBox((HWND)NULL,g_szFormatting, NULL,MB_ICONEXCLAMATION );<br />
		closesocket (conn_socket);<br />
		WSACleanup();<br />
	}<br />
	Sleep(1000);<br />
}<br />
// Close the Winsock and tidy up<br />
closesocket(conn_socket);<br />
WSACleanup();

Mark Salsbery7-Sep-07 5:22

Mark Salsbery

7-Sep-07 5:22

Error 10093 WSANOTINITIALISED Successful WSAStartup not yet performed

Also...

You need to create a proper UDP socket:

conn_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP

); /* Open a socket */<br />
<br />

and sendto() needs a destination address.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

Andy2027-Sep-07 9:13

7-Sep-07 9:13

One final question Mark, if I just want to Broadcast UDP packets out on a local network, what destination address do I use?

how to establish usb communication in MFC?

Moak8-Nov-07 12:37

Moak

8-Nov-07 12:37

Andy202 wrote:
I just want to Broadcast UDP packets out on a local network, what destination address do I use

You could use the limited broadcast address 255.255.255.255, however it is best to use the correct IP broadcast address of your local network segment (more successful in my own experience). You can calculate the correct broadcast address, see here.

/M

Home page

ashokbngr5-Sep-07 22:43

ashokbngr

5-Sep-07 22:43

Hi,

I need any sample..code or advice for usb communication in MFC.
I need to do read and write operations on a usb device.. Confused | :confused:

thanks in advance
Ashok

Re: how to establish usb communication in MFC?

Cedric Moonen5-Sep-07 23:16

Cedric Moonen

5-Sep-07 23:16

Which kind of device are you communicating with ? USB doesn't work like a serial port: you don't have access directly to the port but instead you get the handle of a driver. This driver is shipped with the device you want to communicate with and manages all the communication with the device.

To get the handle of the driver, simply call CreateFile supplying the correct driver name, then you should be able to use ReadFile and WriteFile. You can also do some more specific stuff by calling DeviceIOControl (in which you can pass some specific IO code which is dependent of your driver).

So, if you want more help, you'll need to give a lot more information (which device do you try to access, if you have documentation with it, ...).

Cédric Moonen
Software developer

Charting control [v1.2]

numerical methods

mitsui585-Sep-07 22:00

mitsui58

5-Sep-07 22:00

can anybody help me make a program that can do any of these numerical method?

moss,newton method, secant method, taylor-maclauren,bisection method,gaussian elimination, gauss-seindal,lagrange method.

thanks guys!! Big Grin | :-D

Russell^'5-Sep-07 22:39

Russell^'

5-Sep-07 22:39

homework?

don't tell me that you don't find the way to implement the secant-method or bisection method! Big Grin | :-D

You have only to implement the algorithm:

ask for a function f(x) and for the borders x1 and x2.
check that sign(f(x1)) != sign(f(x2)) .
Then compute x3 inside the interval (x1, x2). This according on the algorithm, in bisection case x3=(x1+x2)/2,....in secant method it's only the point where the line from (x1,f(x1)) to (x2,f(x2)) intercept the x-axe.
then choose the new interval (or x1-x3 or x3-x2) according on where is the root.
Then start again on the new interval.
Do this 10000...000 times and stop it. Or stop when the interval is "too small".

That's it.
Smile | :)

Russell

mitsui585-Sep-07 22:53

mitsui58

5-Sep-07 22:53

thanks russell!

it a project actually.. Smile | :)

Russell^'5-Sep-07 23:13

Russell^'

5-Sep-07 23:13

ok, you convinced me.;)
Then you won this link[^].
Big Grin | :-D

(the routines are in C, not in C++. but it is easy to translate they)

Russell

mitsui587-Sep-07 4:35

mitsui58

7-Sep-07 4:35

thanks for the link Smile | :)

that's really helpful.

David Crow6-Sep-07 3:28

David Crow

6-Sep-07 3:28

mitsui58 wrote:
can anybody help me make a program that can do any of these numerical method?

Yes, I'm sure someone can.

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne