Definition of USOCKET class has the comment the %READY-P slot is reset by SOCKET-ACCEPT function. But right now SOCKET-ACCEPT does not reset it, hence WAIT-FOR-INPUT will not actuall wait after the first it time it notices the readiness. Also, SB-BSD-SOCKETS:SOCKET-ACCEPT may return NIL (if accept call returned EWOULDBLOCK, for example), and USOCKET:SOCKET-ACCEPT will try to use it. Attached is a patch that fixes these two issues.