The ACCEPT, READ, READV, RECV, RECVFROM, and RECVMSG macros are read operations. A socket is ready for reading when data is received on it, or when an exception condition occurs.

To determine if a socket is ready for the read operation, set the appropriate bit in RSNDMSK to 1 before issuing the SELECT macro. When the SELECT macro returns, the corresponding bits in the RRETMSK indicate sockets ready for reading.