摘要：fd_set是一个结构/* The fd_set member is required to be an array of longs. */typedef long int __fd_mask; /* Some versions of define this macros. */#undef __NFDBITS/* It's easier to assume 8-bit bytes than to get CHAR_BIT. */#define __NFDBITS (8 * (int) sizeof (__fd_mask)) //32#define __FD_ELT(d) (... 阅读全文