Hey there,
Welcome to the forum!
IJTS is normally open on Saturday and Sundays, from about 14:00 GMT.
And it is usually in Marseille.
I believe I have that correct!
And if you have a look on the forum at IJTS you will see a little news section and it will say if the server is up or not. (www.ijts.co.uk)
And also sometimes when it is open, it is stated in this topic here: http://80.95.161.114/shipsim/forum/index.php/topic,15480.0.html
I hope you have a good time