Is There Any Way To Close All Existing Connections

I have a site which has extensive database activity. What I do is for each procedure I open a connection to the database and close it as and when I leave the procedure. However, in long run I find that some connection to the database is not properly closed causing the site to hang. This has become a big headache for me.

Trying to find what is going wrong I logged opening /closing of connections to the database and found that at some points the connections are not closed resulting in large no. of active connections to the database.

But if I go through the script I cannot really understand why that connection was not closed since the script ensure that the connection is closed before exiting the procedure.

Is there any way where I can check the database may be during night time and close all existing connections to the database. I repeat all my connections to the database are done at the procedure level.