The Standard ML Basis Library

The NetHostDB structure

Synopsis

signature NET_HOST_DB  (* OPTIONAL *)
structure NetHostDB :> NET_HOST_DB  (* OPTIONAL *)

This structure accesses the information contained in the network host data base. The data might be retrieved from a file such as /etc/hosts on Unix systems, or dynamically via some network communication. The structure can be used to convert host names (e.g., "cs.princeton.edu") to Internet addresses (e.g., "128.112.136.10").

Interface

eqtype in_addr
eqtype addr_family
type entry

val name : entry -> string
val aliases : entry -> string list
val addrType : entry -> addr_family
val addr : entry -> in_addr
val addrs : entry -> in_addr list
val getByName : string -> entry option
val getByAddr : in_addr -> entry option
val getHostName : unit -> string

val toString : in_addr -> string
val scan       : (char, 'a) StringCvt.reader
                   -> (in_addr, 'a) StringCvt.reader
val fromString : string -> in_addr option

Description

eqtype in_addr
The type representing an Internet address.

eqtype addr_family
The type representing address families (also known as domains).

type entry
The type representing an entry from the host database.

name en
returns the official name of the host described by entry en.

aliases en
returns the alias list of the host described by entry en.

addrType en
returns the address family of the host described by entry en.

addr en
returns the main Internet address of the host described by entry en. This is the first address of the list returned by addrs.

addrs en
returns the list of Internet addresses of the host described by entry en. The list is guaranteed to be non-empty.

getByName s
reads the network host data base for a host with name s. If successful, it returns SOME(en) where en is the corresponding data base entry; otherwise, it returns NONE.

getByAddr ia
reads the network host data base for a host with Internet address ia. If successful, it returns SOME(en) where en is the corresponding data base entry; otherwise, it returns NONE.

val getHostName : unit -> string
The standard hostname for the current processor.

toString ia
returns a string representation of the Internet address ia in the form "a.b.c.d".

scan getc strm
fromString s
These functions scan Internet address from a character source. The first returns SOME(ia,rest) if an Internet address can be parsed from a prefix of the character stream strm after skipping initial whitespace. ia is the resulting address, and rest is the remainder of the character stream. NONE is returned otherwise.

The second form returns SOME(ia) if an Internet address ia can be parsed from a prefix of string s. NONE is returned otherwise. It is equivalent to StringCvt.scanString scan.

Addresses in this notation have one of the following forms:

a
where a is a 32-bit unsigned integer constant.
a.b
where a is an 8-bit unsigned integer constant, and b is a 24-bit integer constant.
a.b.c
where a and b are 8-bit unsigned integer constants, and c is a 16-bit integer constant.
a.b.c.d
where a, b, c, and d are 8-bit integer constants.
The integer constants may be decimal, octal, or hexadecimal, as specified in the C language.

See Also

GenericSock, INetSock, NetProtDB, Socket
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Generated April 12, 2004
Last Modified June 5, 1998
Comments to John Reppy.

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