这里是对各种情况解释比较好的链接

ENETUNREACH,ECONNREFUSED ENETUNREACH,ECONNREFUSED​ ENOTSOCK ​​ENOTSOCK​​ EINTR EINTR EADDRINUSE ​​EADDRINUSE​​ EADDRNOTAVAIL EADDRNOTAVAIL EACCES ​​EACCES​​ EPERM ​​EPERM​​ EAFNOSUPPORT ​​EAFNOSUPPORT​​ EBADF,EALREADY ​​EBADF,EALREADY​​ GNU手册
EFAULT EFAULT