1 -*- outline -*-

     2 

     3 * What characters may be used for host name?

     4 

     5 As say RFC 952 hostname is a text string up to 24 characters drawn from the alphabet

     6 (A-Z), digits (0-9), minus sign (-), and period (.).

     7 

     8 As say RFC 1035:

     9 

    10   <domain> ::= <subdomain> | " "

    11 

    12   <subdomain> ::= <label> | <subdomain> "." <label>

    13 

    14   <label> ::= <letter> [ [ <ldh-str> ] <let-dig> ]

    15 

    16   <ldh-str> ::= <let-dig-hyp> | <let-dig-hyp> <ldh-str>

    17 

    18   <let-dig-hyp> ::= <let-dig> | "-"

    19 

    20   <let-dig> ::= <letter> | <digit>

    21 

    22   <letter> ::= any one of the 52 alphabetic characters A through Z in

    23   upper case and a through z in lower case

    24 

    25   <digit> ::= any one of the ten digits 0 through 9