To be honest, sometimes I think that lots of socialisation with other pups is overrated! I don't mean to sound po-faced or miserable, but so many people take their pups to classes and allow or encourage unstructured, free-for-all play, without setting in place rules, even just down to letting it wrestle with the dog next to them while waiting their turn, and then wonder why their pup can't/won't pay them attention! The same applies when out on a walk, letting them play with every dog they see; so what is the pup going to think whenever it sees another dog? PLAYTIME!! There's nothing wrong with allowing a good romp, but it has to be with the understanding that when mum says come, you COME! Then you get something lovely and get to go back and play too!!
I must have looked a real killjoy when Dazzle was a baby at class, but I didn't want her saying hello to every dog she saw, or every person there, I didn't want her mugging others for food because she'd been given titbits by other people, I wanted her to see ME as the most exciting, fun and rewarding thing in her world. As a result we can mix with loose dogs and their people and she ignores them, she's not the least interested in playing until I tell her she can; she does love other people and likes other dogs (as long as they don't get too pushy or bounce all over her) but she'd much rather do stuff with me, and when we're training she has a tendency to tell any dogs that approach to bog off as she's doing stuff with mum, instead of checking out and bogging off.
I've said it before and I'll say it again; a dog that doesn't have a solid recall should be on a long line untill it's trained reliably. Every time the dog runs off it's reinforcing the behaviour of running off and making it more difficult to teach NOT running off. And it's dangerous! Find something that he REALLY loves, I mean goes nutso over, use it as his reward and condition an automatic head-turn response to his name or recall cue, such that he doesn't think just acts. Start it in the house, take it into the garden, a quiet park or field, gradually raise the level of distraction, and for now don't let him self-reward by running off to play with other dogs. If it were my dog I wouldn't let him socialise off-lead with other dogs for now, not until he could focus and listen to me around distractions, and found me amazingly fun and exciting. Then I would allow limited interaction under controlled conditions (using a long line and/or an enclosed space) and use lots and lots of recall/reward/release games.