But based on personal experience in Europe I do find that networking with recruiters is a complete waste of time. Networking with past colleagues and popping into the local meetup scene plus targeted talks with recruiters at industry conferences such as oscon (rip!) are going to give you way better returns.
I've got 20+ years experience in the industry, I've worked at some well-known shops and I have a decent looking CV with some financial sector experience. I do get the regular Google and Facebook recruiters on LinkedIn but would probably not pass their interview because I am already gainfully employed and do not have the time to cram computing trivia to pass their screen. Due to the financial sector experience I seem to get a ton of recruiters from the UK (and now NL), plus an incredible large number of invites to talk about a "devops engineer position" from German recruiters.
Especially the German recruiters are a complete waste of time. They are so terrible, they keep offering junior to mid-level positions to someone with 20yoe and a tech-lead/staff title to match. Their base comp is usually below 50% of my current base, sometimes barely a third. The UK and NL offers are better financially but still not reaching current TC levels. At this point, it's not even worth replying to their LinkedIn or Xing messages.
If you're at the bottom of the market or just starting out, recruiters or headhunters can be helpful to get an in at a company. But once you have a few years experience, their value rapidly declines, especially if you're aiming at the top of the market comp wise. With experience and a network, you know where your friends are working, if they like the places and you have an easy way to get referrals.