Verify host name properly maps to IP addr.

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open System
open System.IO
open System.Net

let hostname = "www.microsoft.com"      // This is the host name of your computer

[<EntryPoint>]
let main argv =     
    let host = Dns.GetHostEntry(hostname)
    let reverseIP = host.AddressList.[0].ToString()
    let req = WebRequest.Create("http://checkip.dyndns.org/")
    let resp = req.GetResponse()
    let stream = resp.GetResponseStream()
    let rdr = new StreamReader(stream)
    let html = rdr.ReadToEnd()
    let first = html.IndexOf("Address: ") + 9
    let last = html.LastIndexOf("</body>")
    let IP = html.Substring(first, last - first)
    if 0 = String.Compare(reverseIP,IP) then
        printfn "Match, ip address for %s = %s" hostname IP
    else
        printfn "Addresses do not match! %s resolves to %s, but local IP address reported as %s"
          hostname reverseIP IP
    Console.ReadKey() |> ignore
    0 // return an integer exit code

namespace System

namespace System.IO

namespace System.Net

val hostname : string

Full name: Script.hostname

Multiple items
type EntryPointAttribute =
  inherit Attribute
  new : unit -> EntryPointAttribute

Full name: Microsoft.FSharp.Core.EntryPointAttribute

--------------------
new : unit -> EntryPointAttribute

val main : argv:string [] -> int

Full name: Script.main

val argv : string []

val host : IPHostEntry

type Dns =
  static member BeginGetHostAddresses : hostNameOrAddress:string * requestCallback:AsyncCallback * state:obj -> IAsyncResult
  static member BeginGetHostByName : hostName:string * requestCallback:AsyncCallback * stateObject:obj -> IAsyncResult
  static member BeginGetHostEntry : hostNameOrAddress:string * requestCallback:AsyncCallback * stateObject:obj -> IAsyncResult + 1 overload
  static member BeginResolve : hostName:string * requestCallback:AsyncCallback * stateObject:obj -> IAsyncResult
  static member EndGetHostAddresses : asyncResult:IAsyncResult -> IPAddress[]
  static member EndGetHostByName : asyncResult:IAsyncResult -> IPHostEntry
  static member EndGetHostEntry : asyncResult:IAsyncResult -> IPHostEntry
  static member EndResolve : asyncResult:IAsyncResult -> IPHostEntry
  static member GetHostAddresses : hostNameOrAddress:string -> IPAddress[]
  static member GetHostByAddress : address:string -> IPHostEntry + 1 overload
  ...

Full name: System.Net.Dns

Dns.GetHostEntry(address: IPAddress) : IPHostEntry
Dns.GetHostEntry(hostNameOrAddress: string) : IPHostEntry

val reverseIP : string

property IPHostEntry.AddressList: IPAddress []

val req : WebRequest

type WebRequest =
  inherit MarshalByRefObject
  member Abort : unit -> unit
  member AuthenticationLevel : AuthenticationLevel with get, set
  member BeginGetRequestStream : callback:AsyncCallback * state:obj -> IAsyncResult
  member BeginGetResponse : callback:AsyncCallback * state:obj -> IAsyncResult
  member CachePolicy : RequestCachePolicy with get, set
  member ConnectionGroupName : string with get, set
  member ContentLength : int64 with get, set
  member ContentType : string with get, set
  member Credentials : ICredentials with get, set
  member EndGetRequestStream : asyncResult:IAsyncResult -> Stream
  ...

Full name: System.Net.WebRequest

WebRequest.Create(requestUri: Uri) : WebRequest
WebRequest.Create(requestUriString: string) : WebRequest

val resp : WebResponse

WebRequest.GetResponse() : WebResponse

val stream : Stream

WebResponse.GetResponseStream() : Stream

val rdr : StreamReader

Multiple items
type StreamReader =
  inherit TextReader
  new : stream:Stream -> StreamReader + 9 overloads
  member BaseStream : Stream
  member Close : unit -> unit
  member CurrentEncoding : Encoding
  member DiscardBufferedData : unit -> unit
  member EndOfStream : bool
  member Peek : unit -> int
  member Read : unit -> int + 1 overload
  member ReadLine : unit -> string
  member ReadToEnd : unit -> string
  ...

Full name: System.IO.StreamReader

--------------------
StreamReader(stream: Stream) : unit
StreamReader(path: string) : unit
StreamReader(stream: Stream, detectEncodingFromByteOrderMarks: bool) : unit
StreamReader(stream: Stream, encoding: Text.Encoding) : unit
StreamReader(path: string, detectEncodingFromByteOrderMarks: bool) : unit
StreamReader(path: string, encoding: Text.Encoding) : unit
StreamReader(stream: Stream, encoding: Text.Encoding, detectEncodingFromByteOrderMarks: bool) : unit
StreamReader(path: string, encoding: Text.Encoding, detectEncodingFromByteOrderMarks: bool) : unit
StreamReader(stream: Stream, encoding: Text.Encoding, detectEncodingFromByteOrderMarks: bool, bufferSize: int) : unit
StreamReader(path: string, encoding: Text.Encoding, detectEncodingFromByteOrderMarks: bool, bufferSize: int) : unit

val html : string

StreamReader.ReadToEnd() : string

val first : int

String.IndexOf(value: string) : int
String.IndexOf(value: char) : int
String.IndexOf(value: string, comparisonType: StringComparison) : int
String.IndexOf(value: string, startIndex: int) : int
String.IndexOf(value: char, startIndex: int) : int
String.IndexOf(value: string, startIndex: int, comparisonType: StringComparison) : int
String.IndexOf(value: string, startIndex: int, count: int) : int
String.IndexOf(value: char, startIndex: int, count: int) : int
String.IndexOf(value: string, startIndex: int, count: int, comparisonType: StringComparison) : int

val last : int

String.LastIndexOf(value: string) : int
String.LastIndexOf(value: char) : int
String.LastIndexOf(value: string, comparisonType: StringComparison) : int
String.LastIndexOf(value: string, startIndex: int) : int
String.LastIndexOf(value: char, startIndex: int) : int
String.LastIndexOf(value: string, startIndex: int, comparisonType: StringComparison) : int
String.LastIndexOf(value: string, startIndex: int, count: int) : int
String.LastIndexOf(value: char, startIndex: int, count: int) : int
String.LastIndexOf(value: string, startIndex: int, count: int, comparisonType: StringComparison) : int

val IP : string

String.Substring(startIndex: int) : string
String.Substring(startIndex: int, length: int) : string

Multiple items
type String =
  new : value:char -> string + 7 overloads
  member Chars : int -> char
  member Clone : unit -> obj
  member CompareTo : value:obj -> int + 1 overload
  member Contains : value:string -> bool
  member CopyTo : sourceIndex:int * destination:char[] * destinationIndex:int * count:int -> unit
  member EndsWith : value:string -> bool + 2 overloads
  member Equals : obj:obj -> bool + 2 overloads
  member GetEnumerator : unit -> CharEnumerator
  member GetHashCode : unit -> int
  ...

Full name: System.String

--------------------
String(value: nativeptr<char>) : unit
String(value: nativeptr<sbyte>) : unit
String(value: char []) : unit
String(c: char, count: int) : unit
String(value: nativeptr<char>, startIndex: int, length: int) : unit
String(value: nativeptr<sbyte>, startIndex: int, length: int) : unit
String(value: char [], startIndex: int, length: int) : unit
String(value: nativeptr<sbyte>, startIndex: int, length: int, enc: Text.Encoding) : unit

String.Compare(strA: string, strB: string) : int
String.Compare(strA: string, strB: string, comparisonType: StringComparison) : int
String.Compare(strA: string, strB: string, ignoreCase: bool) : int
String.Compare(strA: string, strB: string, ignoreCase: bool, culture: Globalization.CultureInfo) : int
String.Compare(strA: string, strB: string, culture: Globalization.CultureInfo, options: Globalization.CompareOptions) : int
String.Compare(strA: string, indexA: int, strB: string, indexB: int, length: int) : int
String.Compare(strA: string, indexA: int, strB: string, indexB: int, length: int, comparisonType: StringComparison) : int
String.Compare(strA: string, indexA: int, strB: string, indexB: int, length: int, ignoreCase: bool) : int
String.Compare(strA: string, indexA: int, strB: string, indexB: int, length: int, culture: Globalization.CultureInfo, options: Globalization.CompareOptions) : int
String.Compare(strA: string, indexA: int, strB: string, indexB: int, length: int, ignoreCase: bool, culture: Globalization.CultureInfo) : int

val printfn : format:Printf.TextWriterFormat<'T> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.printfn

type Console =
  static member BackgroundColor : ConsoleColor with get, set
  static member Beep : unit -> unit + 1 overload
  static member BufferHeight : int with get, set
  static member BufferWidth : int with get, set
  static member CapsLock : bool
  static member Clear : unit -> unit
  static member CursorLeft : int with get, set
  static member CursorSize : int with get, set
  static member CursorTop : int with get, set
  static member CursorVisible : bool with get, set
  ...

Full name: System.Console

Console.ReadKey() : ConsoleKeyInfo
Console.ReadKey(intercept: bool) : ConsoleKeyInfo

val ignore : value:'T -> unit

Full name: Microsoft.FSharp.Core.Operators.ignore