This is the same as
tcp_select/1 (see ipc-tcp-trm-select1), except
tcp_select/2 will return the atom
timeout if the timeout
interval expires before input is available or before a timer alarm is
tcp_schedule_wakeup/2, see ipc-tcp-tim-schedule_wakeup2).
Timeout is a floating point number indicating seconds.
tcp_select predicates must deal with three events:
tcp_select/2will sleep until there is input available from some connected process.
A poll is effected by specifying 0 for Timeout.