You can use RTCS_selectset() but I would not recommend it as it cannot distinguish between write and read activity as POSIX like select(). We consider this function as obsolete and recommend new applications to either use POSIX like select() or multi-task design.
We have introduced POSIX-like select() in last released versions of RTCS and (MQX 4.2.0 will be out very soon). However, even POSIX like select() is useful only for single task design. Example for the single task design with select() is the ECHOSRV application in RTCS 4.2.0. If you wish to have multi task desing, as we have for example in HTTPSRV, FTPSRV applications, you can just create separate task per connected client. In the per-client task you would recv()/send() with the client and then close the socket and destroy the task after communication is done. Exactly this way we do the sessions in HTTPSRV/FTPSRV.
Martin