In RFC 2396, "_" is taken as "Unreserved Characters".
Unreserved characters can be escaped without changing the semantics
of the URI, but this should not be done unless the URI is being
used
in a context that does not allow the unescaped character to appear.
However, URI.escape doesn't escape "_".
require 'URI'
original_uri = "
http://dr_gabriele.podomatic.com/enclosure/"
uri = URI.escape(original_uri)
puts uri == original_uri
I'm no expert on DNS, this is what I have found in appendix A:
host = hostname | IPv4address
hostname = *( domainlabel "." ) toplabel [ "." ]
domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum
toplabel = alpha | alpha *( alphanum | "-" ) alphanum
IPv4address = 1*digit "." 1*digit "." 1*digit "." 1*digit
alphanum = alpha | digit
alpha = lowalpha | upalpha
lowalpha = "a" | "b" | "c" | "d" | "e" | "f" | "g" | "h" | "i" |
"j" | "k" | "l" | "m" | "n" | "o" | "p" | "q" | "r" |
"s" | "t" | "u" | "v" | "w" | "x" | "y" | "z"
upalpha = "A" | "B" | "C" | "D" | "E" | "F" | "G" | "H" | "I" |
"J" | "K" | "L" | "M" | "N" | "O" | "P" | "Q" | "R" |
"S" | "T" | "U" | "V" | "W" | "X" | "Y" | "Z"
digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" |
"8" | "9"
There's no "_" there. YMMV ;-)