Eric Radman

Description

More than ten years after IPv6 was standardized very few corporate systems have adopted it, but the programming interfaces that emerged to support it have already benefited system programmers because the interfaces themselves are protocol agnostic. getaddrinfo(3) provides a mechanism for binding sockets to addresses specified in their native, numeric format, or by a hostname that is resolved according the order specified in /etc/resolv.conf. To start, establish a addrinfo structure with some data about the kind of connection you're trying to make and a pointer to an array of results that the OS is going to give us. *ai will refer to an array because a hostname can refer to more than one protocol family (IPv6 is sorted first). If we actually wanted to listen on more than one address we would have to loop through the results by following the *ai_next pointer. If no error is reported the structure ai can then be used to set up socket(2), bind(2), and then listen(2). The primary goal of kqueue(2) was to create an scalable way to monitor a large number of file descriptors, but kqueue is also a generic, deterministic event notification mechanism. First initialize a queue, then add filters that indicate when an event is to hold true. EV_SET is a macro that simply fills in the kevent structure. The call to kevent(2) indicates that there is one change to kq: the addition of EVFILT_READ. The following loop waits for events and then uses any combination of meaninful conditions to determine what the event is, and what should be done about it. All of the error-checking code has been removed for this example, but if you may want to add some to recognize a singal by testing errno so that you don't try to process them as a kevent() failure

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