Resolve a host or service name to one or more addresses. The AddrInfo values that this function returns contain SocketAddr values that you can use to init TCP connection.

This function is protocol independent. It can return both IPv4 and IPv6 address information.

The AddrInfo argument specifies the preferred query behaviour, socket options, or protocol. You can override these conveniently using Haskell's record update syntax on defaultHints, for example as follows:

>>> let hints = defaultHints { addrFlags = [AI_NUMERICHOST], addrSocketType = Stream }

You must provide non empty value for at least one of the HostName or ServiceName arguments. HostName can be either a numeric network address (dotted quad for IPv4, colon-separated hex for IPv6) or a hostname. In the latter case, its addresses will be looked up unless AI_NUMERICHOST is specified as a hint. If you do not provide a HostName value and do not set AI_PASSIVE as a hint, network addresses in the result will contain the address of the loopback interface.

If the query fails, this function throws an IO exception instead of returning an empty list. Otherwise, it returns a non-empty list of AddrInfo values.

There are several reasons why a query might result in several values. For example, the queried-for host could be multihomed, or the service might be available via several protocols.

Note: the order of arguments is slightly different to that defined for getaddrinfo in RFC 2553. The AddrInfo parameter comes first to make partial application easier.

>>> addr:_ <- getAddrInfo (Just hints) "127.0.0.1" "http"
>>> addrAddress addr
127.0.0.1:80

Either a host name e.g., "haskell.org" or a numeric host address string consisting of a dotted decimal IPv4 address or an IPv6 address e.g., "192.168.0.1".

Either a service name e.g., "http" or a numeric port number.

Flags that control the querying behaviour of getAddrInfo. For more information, see https://tools.ietf.org/html/rfc3493#page-25

Indicate whether the given AddrInfoFlag will have any effect on this system.

Address info

Default hints for address lookup with getAddrInfo.

>>> addrFlags defaultHints
[]
>>> addrFamily defaultHints
AF_UNSPEC
>>> addrSocketType defaultHints
NoSocketType
>>> addrProtocol defaultHints
0

Peek addrinfo linked list.

Resolve an address to a host or service name. This function is protocol independent. The list of NameInfoFlag values controls query behaviour.

If a host or service's name cannot be looked up, then the numeric form of the address or service will be returned.

If the query fails, this function throws an IO exception.

>>> addr:_ <- getAddrInfo (Just defaultHints) "127.0.0.1" "http"
>>> getNameInfo [NI_NUMERICHOST, NI_NUMERICSERV] True True $ addrAddress addr
("127.0.0.1", "80")

Flags that control the querying behaviour of getNameInfo. For more information, see https://tools.ietf.org/html/rfc3493#page-30