You mean by this.socket.close()? It's not working since Uncaught Error: Function "close" not found!.

Here is my current workaround: Before calling net.socket(), I delete all members of MyClass.socket manually:

...
for (var member in this.socket) delete this.socket[member];
this.socket = net.connect(...

Edit:

This workaround seemed to free some memory but obviously does not prevent old sockets from connecting server when possible, hence consuming memory. (I don't understand what is going on...)