Hi Tim, > Afraid not, still get exception.. ok, let's try step by step. (1) make a script with just one line "require 'socket'"; does it work? (2) two lines: local socket = require 'socket' print(socket.connect("localhost", 8172)) (3) two lines with mobdebug: require('mobdebug').start() print "hello" Do you get a (lua) error or do you get an exception (application crash)? Do steps 1 and 2 work? If one of them doesn't work, then the issue is not with the debugger or ZBS. If 2 works, but 3 doesn't work, I'll need to find a machine with similar configuration to yours and try myself. > Head scratching time. What version of luasocket are you running? Are you using your own luasocket or the one that comes with ZBS? Is it statically compiled into your application? Do you run this script from ZBS or outside of it? When you run from ZBS, ZBS will reference its own libraries, which may cause its socket dll to load, which is linked against lua51.dll, which may cause two interpreters to be loaded if your application includes statically linked lua interpreter. This could easily lead to a crash. There are ways to deal with it, but we need to figure out if that's the case. > Is the OS bright enough to not share the luasocket dll? No, this should not be a problem. Paul.