Recommendation: Use only valid characters in hostnames
Tested with firmeware: 1.0.2 and 1.0.4
Note about valid charatcters in domain names from wikipedia:
Restrictions on valid host names Hostnames are composed of series of labels concatenated with dots, as are all domain names. For example, "en.wikipedia.org" is a hostname. Each label must be between 1 and 63 characters long, and the entire hostname has a maximum of 255 characters. RFCs mandate that a hostname's labels may contain only the ASCII letters 'a' through 'z' (case-insensitive), the digits '0' through '9', and the hyphen. Hostname labels cannot begin or end with a hyphen. No other symbols, punctuation characters, or blank spaces are permitted.