Question

为什么GetHostByName总是阻塞的

Answer 1

gethostbyname确实是阻塞的，但应该可以设置一个time_out免得DNS Server出问题时老是执行，关于设置Time_out，参阅一下code:
int timeout = TIMEOUT_VALUE;
int err;
SOCKET s;
s = socket( ... );
err = setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout, sizeof(timeout));