I find it strange that some people I speak to can't seem to accept that you can be alone but not lonely.
And to me the opposite can also be true - you can be surrounded by friends and family and still be very lonely.
Myself, I've been alone but not lonely since childhood, it was a survival thing for me I had to learn to get used to my own company. Recently through my recovery, I do find myself feeling lonely sometimes - but more so when I'm in company. There's probably something else from my past I need to work on but I can't quite put my finger on it. Maybe that's why I like the internet interaction too, it eases the loneliness but I'm not in a crowd as such.