[FreeRTOS+TCP API Reference]
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 FreeRTOSIPConfig.h for FreeRTOS_FD_SET() to be available.
Socket Sets allow an application RTOS task to block on multiple sockets simultaneously.
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 values:
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 is received.
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 is established.
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.
|eSELECT_EXCEPT||The eSELECT_EXCEPT event will become pending if the socket gets disconnected.|
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() documentation page.