I'd recommend using a network library, based on UDP, that adds some TCP-like functionality.
Check the toolbox and code-archive sections of this site linked in the menus on this page. There may be a Blitz compatible solution in there.
Also check out the links below.
http://www.gamedev.net/community/forums/showfaq.asp?forum_id=15
http://www.gamedev.net/reference/list.asp?categoryid=30
http://www.devmaster.net/articles/building-mmorpg/
http://www.devmaster.net/articles/mmorpg-postmortem/part1.php
http://www.devmaster.net/articles/mmo-economy/part1.php
Check the toolbox and code-archive sections of this site linked in the menus on this page. There may be a Blitz compatible solution in there.
Also check out the links below.
http://www.gamedev.net/community/forums/showfaq.asp?forum_id=15
http://www.gamedev.net/reference/list.asp?categoryid=30
http://www.devmaster.net/articles/building-mmorpg/
http://www.devmaster.net/articles/mmorpg-postmortem/part1.php
http://www.devmaster.net/articles/mmo-economy/part1.php