741 		-- Check hostname validity

   742 		do

   743 			local idna = require "util.encodings".idna;

   744 			local invalid_hosts = {};

   745 			local alabel_hosts = {};

   746 			for host in it.filter("*", pairs(configmanager.getconfig())) do

   747 				local _, h, _ = jid_split(host);

   748 				if not h or not idna.to_ascii(h) then

   749 					table.insert(invalid_hosts, host);

   750 				else

   751 					for label in h:gmatch("[^%.]+") do

   752 						if label:match("^xn%-%-") then

   753 							table.insert(alabel_hosts, host);

   754 							break;

   755 						end

   756 					end

   757 				end

   758 			end

   759 

   760 			if #invalid_hosts > 0 then

   761 				table.sort(invalid_hosts);

   762 				print("");

   763 				print("    Your configuration contains invalid host names:");

   764 				print("        "..table.concat(invalid_hosts, "\n        "));

   765 				print("");

   766 				print("    Clients may not be able to log in to these hosts, or you may not be able to");

   767 				print("    communicate with remote servers.");

   768 				print("    Use a valid domain name to correct this issue.");

   769 			end

   770 

   771 			if #alabel_hosts > 0 then

   772 				table.sort(alabel_hosts);

   773 				print("");

   774 				print("    Your configuration contains incorrectly-encoded hostnames:");

   775 				for _, ahost in ipairs(alabel_hosts) do

   776 					print(("        '%s' (should be '%s')"):format(ahost, idna.to_unicode(ahost)));

   777 				end

   778 				print("");

   779 				print("    Clients may not be able to log in to these hosts, or you may not be able to");

   780 				print("    communicate with remote servers.");

   781 				print("    To correct this issue, use the Unicode version of the domain in Prosody's config file.");

   782 			end

   783 

   784 			if #invalid_hosts > 0 or #alabel_hosts > 0 then

   785 				print("");

   786 				print("WARNING: Changing the name of a VirtualHost in Prosody's config file");

   787 				print("         WILL NOT migrate any existing data (user accounts, etc.) to the new name.");

   788 				ok = false;

   789 			end

   790 		end

   791