void FreeRTOS_FD_SET( Socket_t xSocket, SocketSet_t xSocketSet, BaseType_t xSelectBits );
Add a socket to a socket set, and set the event bits of interest for the
added socket. A socket can only be a member of one set at any time.
ipconfigSUPPORT_SELECT_FUNCTION must be set to 1 in
for FreeRTOS_FD_SET() to be available.
Socket Sets allow an application RTOS task to block on multiple sockets
To use a socket set:
Create a socket set by calling FreeRTOS_CreateSocketSet().
A socket set is equivalent to the Berkeley sockets fd_set type.
Add one or more sockets to the set using calls to FreeRTOS_FD_SET().
FreeRTOS_FD_SET() is equivalent to the Berkeley sockets FD_SET() macro.
Call FreeRTOS_Select() to test the
sockets in the set to see if any of the sockets have an event
If FreeRTOS_select() returns a non-zero value then check all
sockets in the set using a call to FreeRTOS_FD_ISSET()
to determine which events are pending.
The event bits of interest are set using the xSelectBits parameter,
which can take a bitwise OR combination of one or more of the following
For a socket that is reading data, the eSELECT_READ event
will be pending in a socket as long as the socket contains
For a socket that is listening for new connections, the
eSELECT_READ event will be pended each time a new connection
The eSELECT_WRITE event will remain pending as long as the
socket has space for writing.
If a TCP socket is actively connecting to a pear the
eSELECT_WRITE event will be triggered as soon as the connection
One the eSELECT_WRITE event has been pended it should either
be disabled, or the caller should write enough data to the
socket so as to completely fill up the transmit buffer –
otherwise the pending eSELECT_WRITE event will not be cleared.
The eSELECT_EXCEPT event will become pending if the socket
The FreeRTOS_FD_CLR() API function is used to
clear event bits or remove a socket from a socket set.
The socket being added to the set.
The socket set to which the socket is being added.
The events that will cause the socket to unblock a call
to FreeRTOS_select(). See the table above for valid
See the example on the FreeRTOS_select()
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