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
