Winsock - FD_WRITE
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Hi all, i am developing client program using WSAAsyncselect() in Winsock2. i have few queries regarding FD_WRITE. i understood that when client is connected to server. There will be FD_WRITE event posted stating that we can send the data to server. However, i want to send data to server based on some other events that the application is interested in. i am not quite sure how the FD_WRITE event will be fired when i want send data to server. here is the pseudo.
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_SOMEOTHEREVENT:
// collect the data. we need to send collected data to sever (right now data is stored in a list).
break;
case WM_SOCKET:
switch (WSAGETSELECTEVENT(lParam))
{
// how to fire this event when application wants to send data ?
case FD_WRITE:break; } break; } return 0;}
Thanks in advance.
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Hi all, i am developing client program using WSAAsyncselect() in Winsock2. i have few queries regarding FD_WRITE. i understood that when client is connected to server. There will be FD_WRITE event posted stating that we can send the data to server. However, i want to send data to server based on some other events that the application is interested in. i am not quite sure how the FD_WRITE event will be fired when i want send data to server. here is the pseudo.
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_SOMEOTHEREVENT:
// collect the data. we need to send collected data to sever (right now data is stored in a list).
break;
case WM_SOCKET:
switch (WSAGETSELECTEVENT(lParam))
{
// how to fire this event when application wants to send data ?
case FD_WRITE:break; } break; } return 0;}
Thanks in advance.
Your application will receive an
FD_WRITEevent shortly after a connection is made. If your "write" operation receives aWSAEWOULDBLOCKresult, your application will find out that sends are again possible when anFD_WRITEnetwork event is recorded and the associated event object is set."One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
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Your application will receive an
FD_WRITEevent shortly after a connection is made. If your "write" operation receives aWSAEWOULDBLOCKresult, your application will find out that sends are again possible when anFD_WRITEnetwork event is recorded and the associated event object is set."One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
Hi David, Thanks for your reply. i am sorry, i couldn't get what you mean. i understand that application will receive an FD_WRITE event shortly after a connection is made but there is no data to send at that time. here is scenario i am trying for 1) connect to server 2) Connection established - FD_WRITE event is receive. 3) there is no data to send to server 4) some other event fired (not related to socket) -- data arrived, so store the data. 5) now data is available to send to server in the above steps 4 and 5 will happen one after the another. how can i raise FD_Write event after the data is available (means step 4) ?
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Hi David, Thanks for your reply. i am sorry, i couldn't get what you mean. i understand that application will receive an FD_WRITE event shortly after a connection is made but there is no data to send at that time. here is scenario i am trying for 1) connect to server 2) Connection established - FD_WRITE event is receive. 3) there is no data to send to server 4) some other event fired (not related to socket) -- data arrived, so store the data. 5) now data is available to send to server in the above steps 4 and 5 will happen one after the another. how can i raise FD_Write event after the data is available (means step 4) ?
Vijjuuu. wrote:
how can i raise FD_Write event after the data is available (means step 4) ?
Why would you need to raise the
FD_WRITEevent? It is sent to your application to let it know that it can now send data to the socket."One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
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Vijjuuu. wrote:
how can i raise FD_Write event after the data is available (means step 4) ?
Why would you need to raise the
FD_WRITEevent? It is sent to your application to let it know that it can now send data to the socket."One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
Thanks again David, i understood that its lets application know that it can send data to the socket, but when there is no data to send ? and does it mean after initial FD_Write (the time after connection established) , FD_WRITE will be polled to application to let know that it can send data ? i really appreciate your patience. Thanks.
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Thanks again David, i understood that its lets application know that it can send data to the socket, but when there is no data to send ? and does it mean after initial FD_Write (the time after connection established) , FD_WRITE will be polled to application to let know that it can send data ? i really appreciate your patience. Thanks.
Vijjuuu. wrote:
...but when there is no data to send ?
Then don't send any.
Vijjuuu. wrote:
and does it mean after initial FD_Write (the time after connection established) , FD_WRITE will be polled to application to let know that it can send data ?
Did you read the documentation that goes with that event? Your application gets the initial
FD_WRITEevent which means it can start sending data to the socket. In the event that whatever "send" function you are using returnsWSAEWOULDBLOCK, you would then have to wait for the nextFD_WRITEevent to resume sending data to the socket."One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
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Hi all, i am developing client program using WSAAsyncselect() in Winsock2. i have few queries regarding FD_WRITE. i understood that when client is connected to server. There will be FD_WRITE event posted stating that we can send the data to server. However, i want to send data to server based on some other events that the application is interested in. i am not quite sure how the FD_WRITE event will be fired when i want send data to server. here is the pseudo.
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_SOMEOTHEREVENT:
// collect the data. we need to send collected data to sever (right now data is stored in a list).
break;
case WM_SOCKET:
switch (WSAGETSELECTEVENT(lParam))
{
// how to fire this event when application wants to send data ?
case FD_WRITE:break; } break; } return 0;}
Thanks in advance.
As I understand it, the FD_WRITE message means you have a connection and room in the output buffer to accept data. After you get FD_WRITE, use send() to send data when you have it.