I sure do know how it feels to be in that boat! Introverted software developer here, and the first several times I went to such an event I didn't talk to anyone. The talks are usually cool, but I have found that you can meet some pretty cool people, and you'd be surprised who you'll run into over and over again in those circles, so I always felt like I'd missed out on an opportunity afterwards.
An approach that has worked somewhat for me is that when I go to such an event I make it a goal to meet some number of people (started small, like 5 people), get to know a little bit about them, and get a business card if they carry one (Mostly just to keep myself honest at the end of the day, plus makes it easier to get in touch with them later!). Most of the time I found that by the time I'd talked to a few people, I was past most of the resistance and could continue talking to other people.
Obviously, everyone's different and that might not work for you. For me, just showing up is still the hardest part. I have a real hell of a time getting myself out the door and to events like this, and generally have to fight my way through being a nervous wreck leading up to it.