svc_fds
extern int svc_fds;
int svc_fds = 0;
svc_fds |= (1 << sock);
svc_fds &= ~(1 << sock);
int readfds = rdfds & svc_fds;
readfds = svc_fds;
extern int svc_fds;
readfds = svc_fds;
readfds = svc_fds;
readfds = svc_fds;